ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (4,270)
  • Oxford University Press  (4,270)
  • American Chemical Society (ACS)
  • 2015-2019  (2,645)
  • 1990-1994  (679)
  • 1980-1984  (665)
  • 1960-1964
  • 1925-1929  (281)
  • 2019  (712)
  • 2018  (1,075)
  • 2017  (858)
  • 1992  (679)
  • 1982  (665)
  • 1926  (177)
  • 1925  (104)
  • Mathematics  (4,096)
  • Geography  (174)
  • Psychology
Collection
  • Articles  (4,270)
Source
Publisher
Years
  • 2015-2019  (2,645)
  • 1990-1994  (679)
  • 1980-1984  (665)
  • 1960-1964
  • 1925-1929  (281)
Year
Journal
Topic
  • 1
    facet.materialart.
    Unknown
    Instability in the self-similar motion of a planar solidification front (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Understanding the solidification process of a binary alloy is important if one is to control the microstructure obtained during the casting of metals. Whilst much work has been done on the steady-state solidification problem, despite their relevance to metallurgical applications, there is less known about non-steady solidification problems and their stability. In the paper we shall consider the non-steady solidification problem in which the planar solidification front moves in a self-similar manner, in both infinite and semi-infinite planar 1D geometries. For each geometry exact solutions are known for the resulting Stefan problem. We direct our attention to the stability of each solution, demonstrating that whilst the concentration and thermal solutions remain stable, the interface corresponding to the solidification front can develop instabilities. For each geometry, we find that there are always unstable perturbations, although we observe qualitative differences in the form of the unstable perturbations for each case. These results generalize and extend several existing studies in the literature, and throw light on the instability inherent in the non-steady solidification process.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Reproducibility (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper has been removed, as it is a duplicate version. The citation information for the final Editorial is as follows:
    Print ISSN: 1471-678X
    Electronic ISSN: 1471-6798
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Cluster-based supply chain logistics: a case study of a Ukrainian food distributor (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This article deals with the logistics of a Ukrainian food and consumer goods distributor. Our main goal is to reduce the field costs of the company, which comprise the agent labour costs and company's transportation charges. The mathematical model used is an integer programming optimization one. The problem is heuristically decomposed into subproblems; methods to solve these subproblems are presented. In order to reduce company costs one is able to reduce company agents' staff, to optimize agents' daily routes, to minimize overall goods delivery charges and to reduce the number of rented vehicles. The developed software system offers considerable field costs reduction (28%), decision-making transparency for the planning group and a less prominent influence of human factors on decisions and schedules.
    Print ISSN: 1471-678X
    Electronic ISSN: 1471-6798
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    The vector derivative nonlinear Schrödinger equation on the half-line (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this paper, we analyse initial-boundary problems for the vector derivative nonlinear Schrödinger equation on the semi-infinite strip $(x, t) \in (0,\infty )\times (0, T)$ via the unified transform method of Fokas. Even though additional technical complications arise in the vector case compared with scalar ones, we show that it also can be expressed in terms of the solution of a matrix Riemann–Hilbert problem. The Riemann–Hilbert problem involves a jump matrix, uniquely defined in terms of four matrix functions called spectral functions and denoted by { a ( λ ), b ( λ ), A ( λ ), B ( λ )} that depend on the initial data and all boundary values, respectively. A key role is played by the so-called global relation which involves the known and unknown boundary values. By analysing the global relation, we present an effective characterization of the latter two spectral functions in terms of the given initial and boundary data.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Optimal investment and consumption in a continuous-time co-integration model (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper discusses an optimal investment–consumption problem in a continuous-time co-integration model, where an investor aims to maximize an expected, discounted utility derived from intertemporal consumption and terminal wealth in a finite time horizon. Using the dynamic programming principle approach, we obtain an Hamilton–Jacobi–Bellman equation related to the problem. In each of the power and logarithmic utility cases, we obtain semi-closed-form expressions of the investment–consumption strategy and the value function. We also provide some numerical examples to illustrate these theoretical results.
    Print ISSN: 1471-678X
    Electronic ISSN: 1471-6798
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Bayesian joint modelling of the health profile and demand of home care patients (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The estimation of uncertain future patient demands is a key factor for the appropriate planning of human and material resources in health care facilities, where unplanned demand variations may impact the quality of schedules and, consequently, of the provided services. This issue is even more important for health services that are provided outside of hospitals, e.g. for home care (HC) services, where patients are assisted for longer periods and additional planning decisions related to the service delivery in the territory must be taken. With the goal of helping HC management to make robust decisions, we propose a Bayesian model for the estimation and prediction of both the demand for care and the history of health conditions for patients under the charge of HC services. In particular, in this study, we jointly model the temporal evolution of patient care profiles and the weekly number of visits required to nurses. The model is built so that the prediction can be easily computed by means of a Gibbs sampler. To shed light on the features and the applicative impact of our model, we have applied it to data collected from one of the largest Italian HC providers.
    Print ISSN: 1471-678X
    Electronic ISSN: 1471-6798
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    Shape-constrained partial identification of a population mean under unknown probabilities of sample selection (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description:   Estimating a population mean from a sample obtained with unknown selection probabilities is important in the biomedical and social sciences. Using a ratio estimator, Aronow & Lee (2013) proposed a method for partial identification of the mean by allowing the unknown selection probabilities to vary arbitrarily between two fixed values. In this paper, we show how to use auxiliary shape constraints on the population outcome distribution, such as symmetry or log-concavity, to obtain tighter bounds on the population mean. We use this method to estimate the performance of Aymara students, an ethnic minority in the north of Chile, in a national educational standardized test. We implement this method in the R package scbounds.
    Print ISSN: 0006-3444
    Electronic ISSN: 1464-3510
    Topics: Biology , Mathematics , Medicine
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    A robust goodness-of-fit test for generalized autoregressive conditional heteroscedastic models (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description:   The estimation of time series models with heavy-tailed innovations has been widely discussed, but corresponding goodness-of-fit tests have attracted less attention, primarily because the autocorrelation function commonly used in constructing goodness-of-fit tests necessarily imposes certain moment conditions on the innovations. As a bounded random variable has finite moments of all orders, we address the problem by first transforming the residuals with a bounded function. More specifically, we consider the sample autocorrelation function of the transformed absolute residuals of a fitted generalized autoregressive conditional heteroscedastic model. With the corresponding residual empirical distribution function naturally employed as the transformation, a robust goodness-of-fit test is then constructed. The asymptotic distributions of the test statistic under the null hypothesis and local alternatives are derived, and Monte Carlo experiments are conducted to examine finite-sample properties. The proposed test is shown to be more powerful than existing tests when the innovations are heavy-tailed.
    Print ISSN: 0006-3444
    Electronic ISSN: 1464-3510
    Topics: Biology , Mathematics , Medicine
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Robust and consistent variable selection in high-dimensional generalized linear models (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description:   Generalized linear models are popular for modelling a large variety of data. We consider variable selection through penalized methods by focusing on resistance issues in the presence of outlying data and other deviations from assumptions. We highlight the weaknesses of widely-used penalized M-estimators, propose a robust penalized quasilikelihood estimator, and show that it enjoys oracle properties in high dimensions and is stable in a neighbourhood of the model. We illustrate its finite-sample performance on simulated and real data.
    Print ISSN: 0006-3444
    Electronic ISSN: 1464-3510
    Topics: Biology , Mathematics , Medicine
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Two-sample tests of high-dimensional means for compositional data (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description:   Compositional data are ubiquitous in many scientific endeavours. Motivated by microbiome and metagenomic research, we consider a two-sample testing problem for high-dimensional compositional data and formulate a testable hypothesis of compositional equivalence for the means of two latent log basis vectors. We propose a test through the centred log-ratio transformation of the compositions. The asymptotic null distribution of the test statistic is derived and its power against sparse alternatives is investigated. A modified test for paired samples is also considered. Simulations show that the proposed tests can be significantly more powerful than tests that are applied to the raw and log-transformed compositions. The usefulness of our tests is illustrated by applications to gut microbiome composition in obesity and Crohn’s disease.
    Print ISSN: 0006-3444
    Electronic ISSN: 1464-3510
    Topics: Biology , Mathematics , Medicine
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 11
    facet.materialart.
    Unknown
    Erratum: Lower bounds for the height in Galois extensions(Bull. London Math. Soc. 48 (2016) 1008–1012) (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Print ISSN: 0024-6093
    Electronic ISSN: 1469-2120
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 12
    facet.materialart.
    Unknown
    Profinite groups with NIP theory and p-adic analytic groups (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We consider profinite groups as 2-sorted first-order structures, with a group sort, and a second sort that acts as an index set for a uniformly definable basis of neighbourhoods of the identity. It is shown that if the basis consists of all open subgroups, then the first-order theory of such a structure is NIP (that is, does not have the independence property) precisely if the group has a normal subgroup of finite index that is a direct product of finitely many compact $p$-adic analytic groups, for distinct primes $p$. In fact, the condition NIP can here be weakened to NTP${}_2$. We also show that any NIP profinite group, presented as a 2-sorted structure, has an open prosoluble normal subgroup.
    Print ISSN: 0024-6093
    Electronic ISSN: 1469-2120
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 13
    facet.materialart.
    Unknown
    On the formation of small-time curvature singularities in vortex sheets (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The Kelvin–Helmholtz model for the evolution of an infinitesimally thin vortex sheet in an inviscid fluid is mathematically ill-posed for general classes of initial conditions. However, if the initial data, say imposed at t = 0, are in a certain class of analytic functions then the problem is well-posed for a finite time until a singularity forms, say at t = t s , on the vortex-sheet interface, e.g. as illustrated by Moore ( 1979 , The spontaneous appearance of a singularity in the shape of an evolving vortex sheet. Proc. Roy. Soc. Lond. A , 365 , 105–119). However, if the problem is analytically continued into the complex plane, then the singularity, or singularities, exist for t 〈 t s away from the physical real axis. More specifically, Cowley et al. ( 1999 , On the formation of Moore curvature singularities in vortex sheets. J. Fluid Mech. , 378 , 233–267) found that for a class of analytic initial conditions, singularities can form in the complex plane at t = 0+. They posed asymptotic expansions in the neighbourhood of these singularities for 0 〈 t ≪ 1 and found numerical solutions to the governing similarity differential equations. In this paper we obtain new exact solutions to these equations, show that the singularities always correspond to local ${\textstyle \frac {3}{2}}$-power singularities and determine both the number and precise locations of all branch points. Further, our analytical approach can be extended to a more general class of initial conditions. These new exact solutions can assist in resolving the small-time behaviour for the numerical solution of the Birkhoff–Rott equations.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 14
    facet.materialart.
    Unknown
    Model reduction of discrete-time linear systems using Meixner-like filters (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we explore the use of the Meixner-like functions in estimating transfer functions of linear discrete-time systems. By expanding transfer functions with some suitable orthonormal basis functions, it is possible to reduce the estimate parameter number. Thus far, many orthonormal functions have been widely used in this framework such as Laguerre functions and Kautz functions. However, when the system have a slow initial onset or delay, Meixner-like functions, which have a slow start, are more suitable in terms of providing a more accurate approximation to the system. In this article, a minimal state-space realizations for discrete-time linear systems are derived using Meixner-like filters. Further we propose, from input/output measurements, an iterative optimization algorithm for the free parameter (Meixner-like pole) of the Meixner-like filters. The method consists in applying the Newton–Raphson's technique in which their elements are expressed analytically by using the derivative of the Meixner-like functions.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 15
    facet.materialart.
    Unknown
    An ℋ∞ approach to data-driven simultaneous fault detection and control (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper proposes a data-driven ℋ∞ approach to simultaneous fault detection and control problem. This problem is formulated as a time domain ℋ∞ optimization problem and its solution produces a data-driven ℋ∞ controller/detector unit of modest complexity which is capable of achieving some control and fault detection objectives. The mathematical model is assumed to be unknown and only input/output data are used for controller/detector designing. The tradeoff between these objectives is established by tuning a scalar parameter and some weighting matrices. An easily implementable algorithm summarizes the methodology presented in the paper. The proposed algorithm is applied to a numerical example in order to illustrate its effectiveness.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 16
    facet.materialart.
    Unknown
    Stable variational approximations of boundary value problems for Willmore flow with Gaussian curvature (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We study numerical approximations for geometric evolution equations arising as gradient flows for energy functionals that are quadratic in the principal curvatures of a two-dimensional surface. Besides the well-known Willmore and Helfrich flows, we will also consider flows involving the Gaussian curvature of the surface. Boundary conditions for these flows are highly nonlinear, and we use a variational approach to derive weak formulations, which naturally can be discretized with the help of a mixed finite element method. Our approach uses a parametric finite element method, which can be shown to lead to good mesh properties. We prove stability estimates for a semidiscrete (discrete in space, continuous in time) version of the method and show existence and uniqueness results in the fully discrete case. Finally, several numerical results are presented involving convergence tests, as well as the first computations with Gaussian curvature and/or free or semifree boundary conditions.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 17
    facet.materialart.
    Unknown
    Convection and total variation flow—erratum and improvement (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper includes an erratum to ( Bouchut et al. (2014) Convection and total variation flow. IMA J. Numer. Anal., 34 , 1037–1071.) which deals with a nonlinear hyperbolic scalar conservation law, regularized by the total variation flow operator (or 1-Laplacian), and in which a mistake occurred in the convergence proof of the numerical scheme to the continuous entropy solution. For correcting the proof, it is necessary to introduce an additional vanishing viscous term in the scheme. This modification requires casting the whole paper in the framework of discrete and continuous solutions with unbounded support. This new version, nevertheless, leads to a better result than the previous one, since the bounded variation regularity and the compactness of the support of the initial data are no longer assumed.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 18
    facet.materialart.
    Unknown
    Stabilization of an Euler–Bernoulli beam system with a tip mass subject to non-uniform bounded disturbance (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We consider the stabilization problem of an Euler-Bernoulli beam with tip mass, which undergoes non-uniform bounded disturbance. We employ the idea of active disturbance rejection control to design a disturbance estimator that has a time-varying gain of exponential-type, and design a feedback controller, in which the estimate of disturbance is used to cancel the effect of disturbance. We apply the semigroup theory to prove the well-posedness of the resulting closed system. We prove the exponential stability of the closed loop system by the Lyapunov function approach. Some numerical simulations are given to support these results.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 19
    facet.materialart.
    Unknown
    Erratum “A second-order sequential optimality condition associated to the convergence of optimization algorithms” (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The order of the author listing was previously incorrect, and the email address for Paulo J. S. Silva was omitted. This has now been corrected online and in the print issue.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 20
    facet.materialart.
    Unknown
    Proof by model: a new knowledge-based reachability analysis methodology for Petri net (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: To solve the state explosion problem in the reachability analysis of Petri nets, Chao recently broke the NP(nondeterministic polynomial time)-complete barrier by developing the first closed-form solution of the number of Control Related States for the kth-order system. In this paper, we propose a new proof methodology known as proof by model, which is based on the validated information of the reverse net, to simplify and accelerate the construction of the closed-form solution for Petri nets. Here, we apply this methodology to the proof procedure of Top-Right systems with one non-sharing resource placed in the top position of the right-side process. The core theoretical and data basis are that any forbidden (resp. live) state in a Petri net is non-reachable (resp. live) in its reverse net; and the validated information of the Bottom-Right system, the reverse net of Top-Right .
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 21
    facet.materialart.
    Unknown
    H(div) conforming and DG methods for incompressible Euler’s equations (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: H(div) conforming and discontinuous Galerkin (DG) methods are designed for incompressible Euler’s equation in two and three dimension. Error estimates are proved for both the semidiscrete method and fully-discrete method using backward Euler time stepping. Numerical examples exhibiting the performance of the methods are given.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 22
    facet.materialart.
    Unknown
    Trigonometric time integrators for the Zakharov system (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The main challenge in the analysis of numerical schemes for the Zakharov system originates from the presence of derivatives in the nonlinearity. In this article, a new trigonometric time-integration scheme for the Zakharov system is constructed and convergence is proved. The time-step restriction is independent of a spatial discretization. Numerical experiments confirm the findings.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 23
    facet.materialart.
    Unknown
    Pure vorticity formulation and Galerkin discretization for the Brinkman equations (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We introduce a new finite element method for the approximation of the three-dimensional Brinkman problem formulated in terms of the velocity, vorticity and pressure fields. The proposed strategy exhibits the advantage that, at the continuous level, a complete decoupling of vorticity and pressure can be established under the assumption of sufficient regularity. The velocity is then obtained as a simple postprocess from vorticity and pressure, using the momentum equation. Well-posedness follows straightforwardly by the Lax–Milgram theorem. The Galerkin scheme is based on Nédélec and piecewise continuous finite elements of degree $k\ge1$ for vorticity and pressure, respectively. The discrete setting uses the very same ideas as in the continuous case, and the error analysis for the vorticity scheme is carried out first. As a byproduct of these error bounds and the problem decoupling, the convergence rates for the pressure and velocity are readily obtained in the natural norms with constants independent of the viscosity. We also present details about how the analysis of the method is modified for axisymmetric, meridian Brinkman flows; and modify the decoupling strategy to incorporate the case of Dirichlet boundary conditions for the velocity. A set of numerical examples in two and three spatial dimensions illustrate the robustness and accuracy of the finite element method, as well as its competitive computational cost compared with recent fully mixed and augmented formulations of incompressible flows.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 24
    facet.materialart.
    Unknown
    Numerical long-time energy conservation for the nonlinear Schrödinger equation (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Long-time near-conservation of energy by the widely used split-step Fourier method applied to the cubic nonlinear Schrödinger on a torus is investigated. For initial values that are small in the Sobolev space $H^1$, it is shown that the energy is nearly preserved on time intervals that scale polynomially in the inverse of the size of the initial values. This result holds under a nonresonance condition on the time step size of the method. It is shown with the help of a completely resonant modulated Fourier expansion.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 25
    facet.materialart.
    Unknown
    A $C^0$ linear finite element method for two fourth-order eigenvalue problems (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we construct a $C^0$ linear finite element method for two fourth-order eigenvalue problems: the biharmonic and the transmission eigenvalue problems. The basic idea of our construction is to use gradient recovery operator to compute the higher-order derivatives of a $C^0$ piecewise linear function, which do not exist in the classical sense. For the biharmonic eigenvalue problem, the optimal convergence rates of eigenvalue/eigenfunction approximation are theoretically derived and numerically verified. For the transmission eigenvalue problem, the optimal convergence rate of the eigenvalues is verified by two numerical examples: one for constant refraction index and the other for variable refraction index. Compared with existing schemes in the literature, the proposed scheme is straightforward and simpler, and computationally less expensive to achieve the same order of accuracy.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 26
    facet.materialart.
    Unknown
    Avoiding order reduction when integrating linear initial boundary value problems with Lawson methods (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Exponential Lawson methods are well known to have a severe order reduction when integrating stiff problems. In a previous article, the precise order observed with Lawson methods when integrating linear problems is justified in terms of different conditions of annihilation on the boundary. In fact, the analysis of convergence with all exponential methods when applied to parabolic problems has always been performed under assumptions of vanishing boundary conditions for the solution. In this article, we offer a generalization of Lawson methods to approximate problems with nonvanishing and even time-dependent boundary values. This technique is cheap and allows to avoid completely order reduction independently of having vanishing or nonvanishing boundary conditions.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 27
    facet.materialart.
    Unknown
    The web is watching you: A comprehensive review of web-tracking techniques and countermeasures (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-06
    Description: Web tracking is a commonly-used practice on the Internet devoted to retrieve user information for activities such as personalization or advertisement. These techniques are said to drive the web economy, although they are commonly used to invade users' privacy. In the last years, a general concern raised about web tracking, looking forward to combat it in many ways like regulations, anti-tracking methods and even standardization. In this paper, we analyze and discuss the current techniques for web-tracking as well as techniques for its detection and analysis, and countermeasures to prevent web tracking.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 28
    facet.materialart.
    Unknown
    Editorial: Special Issue CISIS15-IGPL (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-06
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 29
    facet.materialart.
    Unknown
    Architecture for adaptable smart spaces oriented on user privacy (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-06
    Description: Smart spaces are populated by users having evolving preferences that, directly or indirectly, reflect their spatial, temporal, financial and interaction patterns of service usage. These data, if disclosed, could draw a detailed picture of users’ life in public spaces. Protection of privacy-sensitive data is especially significant in scenarios employing negotiations where many non-trusted service providers, service consumers and payment processes are involved. For such scenarios an architecture and a protocol for secure and privacy-preserving smart space usage have been developed. The presented approach relies on a trusted party operating as a public service in the ‘security infrastructure as a service’ model. The solution is designed to minimize the risk of users privacy violation from the side of service providers and attackers impersonating regular users, as well as the risk of violating privacy of users’ payment patterns from the side of payment authorities. All parties benefit from fast and secure micropayments allowing for pay-per-use model implementation, which fulfils the non-invasiveness requirement of ubiquitous services. The presented use case scenario illustrates the possible application of this approach, and adversary model explains its privacy attributes.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 30
    facet.materialart.
    Unknown
    Packets tokenization methods for web layer cyber security (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-06
    Description: In this article we address the problem of automated Hypertext Transfer Protocol (HTTP) request structure analysis applied to web layer cyber attacks detection. In this method, we propose a multiple HTTP sequences clustering algorithm combined with the machine-learnt classifier. The main goal behind this approach is the fact that we use the request structure and the statistical measurements of its content in order to detect anomalous behaviour of connections established between client and server. One of the advantages of the proposed method is that our solution does not need any prior knowledge about protocols and APIs that use HTTP as a transportation layer (e.g. RESTFull API, SOAP, etc.). Our experiments prove that the proposed method can achieve satisfactory results and is competitive to other state-of-the-art solutions.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 31
    facet.materialart.
    Unknown
    Key features for the characterization of Android malware families (2017)
    Oxford University Press
    Details
    Publication Date: 2017-01-06
    Description: In recent years, mobile devices such as smartphones, tablets and wearables have become the new paradigm of user–computer interaction. The increasing use and adoption of such devices is also leading to an increased number of potential security risks. The spread of mobile malware, particularly on popular and open platforms such as Android, has become a major concern. This paper focuses on the bad-intentioned Android apps by addressing the problem of selecting the key features of such software that support the characterization of such malware. The accurate detection and characterization of this software is still an open challenge, mainly due to its ever-changing nature and the open distribution channels of Android apps. Maximum relevance minimum redundancy and evolutionary algorithms guided by information correlation measures have been applied for feature selection on the well-known Android Malware Genome (Malgenome) dataset, attaining interesting results on the most informative features for the characterization of representative families of existing Android malware.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 32
    facet.materialart.
    Unknown
    Dynamic discrete models for the granular matter formation process (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this paper, we introduce a new modelling approach for the dynamic granular matter formation process in the form of a system of difference equations, directly tailored to the physical nature of the process at hand. Respectively, the dynamic 1D and 2D discrete models, proposed in this paper, are not constructed as numerical schemes approximating some partial differential equations (PDEs). We propose here to look for the functions describing the standing and the rolling layers of the granular matter as the limits of discrete solutions to the aforementioned model equations as the size of the mesh tends to zero. In particular, this approach allows us to differentiate between the influx of the rolling layer coming down from different directions to the corner points of the standing layer. Such points are difficult to adequately describe by means of PDEs and their straightforward numerical approximations, typically ‘ignoring’ the system's behaviour on the sets of zero measure. However, these points are critical for understanding the dynamics of formation process when the standing layer is created by the moving front of the rolling matter or when the latter is filling a cavity and/or stops rolling. The existence of distributed (infinite-dimensional) limit solutions to our discrete models as the size of the mesh tends to zero is also discussed. We illustrate our findings by numerical examples which use our models as the direct algorithm.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 33
    facet.materialart.
    Unknown
    A hybrid approach for the implementation of the Heston model (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We propose an efficient hybrid tree/finite difference method in order to approximate the Heston model (and possibly other stochastic volatility models). We prove the convergence by embedding the procedure in a bivariate Markov chain and we study the approximation of European and American option prices. We finally provide numerical experiments that give accurate option prices in the Heston model, showing the reliability and the efficiency of the algorithm.
    Print ISSN: 1471-678X
    Electronic ISSN: 1471-6798
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 34
    facet.materialart.
    Unknown
    The solution bounds and fixed point iterative algorithm for the discrete coupled algebraic Riccati equation applied to automatic control (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, applying the special properties of nonnegative matrices and symmetric matrices, we consider the coupled term as a whole and derive the solution bounds of the discrete coupled algebraic Riccati equation. This reduces the error of taking apart the coupled term separately when applying inequality techniques to get the bounds in general. Then, using Cauchy–Schwarz inequality, matrix norm inequalities and a fixed point theorem, we discuss the existence uniqueness condition and fixed point iteration for the solution of this equation. Finally, we offer corresponding numerical examples to illustrate the effectiveness of our results.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 35
    facet.materialart.
    Unknown
    Uniform asymptotics as a stationary point approaches an endpoint (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We obtain the rigorous uniform asymptotics of a particular integral where a stationary point is close to an endpoint. There exists a general method introduced by Bleistein for obtaining uniform asymptotics in this situation. However, this method does not provide rigorous estimates for the error. Indeed, the method of Bleistein starts with a change of variables, which implies that the parameter governing how close the stationary point is to the endpoint appears in several parts of the integrand, and this means that one cannot obtain general error bounds. By adapting the above method to our particular integral, we obtain rigorous uniform leading-order asymptotics. We also give a rigorous derivation of the asymptotics to all orders of the same integral; the novelty of this second approach is that it does not involve a global change of variables.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 36
    facet.materialart.
    Unknown
    Factorization of a class of 2 × 2 matrix symbols by reduction to a scalar factorization (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Using the reduction of a vector Riemann–Hilbert problem on the unit circle to a scalar problem on a contour in a Riemann surface, a factorization method for a class of symbols is described. The class of symbols involves outer functions and rational functions of the square root of a quotient of first degree polynomials. An application to a problem in the field of integrable systems of infinite dimension is presented.
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 37
    facet.materialart.
    Unknown
    Using electric fields to induce patterning in leaky dielectric fluids in a rod-annular geometry (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The stability and axisymmetric deformation of two immiscible, viscous, perfect or leaky dielectric fluids confined in the annulus between two concentric cylinders are studied in the presence of radial electric fields. The fields are set up by imposing a constant voltage potential difference between the inner and outer cylinders. We derive a set of equations for the interface in the long-wavelength approximation which retains the essential physics of the system and allows for interfacial deformations to be as large as the annular gap hence accounting for possible touchdown at the inner or outer electrode. The effects of the electric parameters are evaluated initially by performing a linear stability analysis which shows excellent agreement with the linear theory of the full axisymmetric problem in the appropriate long-wavelength regime. The non-linear interfacial dynamics are investigated by carrying out direct numerical simulations of the derived long wave models, both in the absence and presence of electric fields. For non-electrified thin layer flows (i.e. one of the layers thin relative to the other) the long-time dynamics agree with the lubrication approximation results found in literature. When the liquid layers have comparable thickness our results demonstrate the existence of both finite-time and infinite-time singularities (asymptotic touching solutions) in the system. It is shown that a two-side touching solution is possible for both the non-electrified and perfect dielectric cases, while only one-side touching is found in the case of leaky dielectric liquids, where the flattened interface shape resembles the pattern solutions found in literature. Meanwhile the finite-time singular solution agrees qualitatively with the experiments of Reynolds (1965, Stability of an electrostatically supported fluid column. Phys. Fluids , 8 , 161–170).
    Print ISSN: 0272-4960
    Electronic ISSN: 1464-3634
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 38
    facet.materialart.
    Unknown
    On the controllability of hyperbolic linear systems with constraints on the gradient (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We present some results concerning the controllability of a hyperbolic linear equation with constraints on the gradient, we're interested in an internal subregion of the system evolution domain Ω. We analyse the controllability problem with constraints (also called the enlarged controllability) with distributed control that ensures the transfer of our system to a final desired gradient between two prescribed profiles f1 and f2. The proofs use a sub-differential approach, the Lagrangian one, and finally numerical results are illustrated.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 39
    facet.materialart.
    Unknown
    Deadlock Control Based on Capacity Restrictions for FMS (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In flexible manufacturing systems (FMS), deadlock prevention is an important problem to be solved. Petri nets are a powerful tool and wildly used to model and control FMS. Based on the capacity restrictions for activity places in the Petri net model of an FMS, a new approach is presented to implement the liveness of the controlled net system in this research. First, given a Petri net prone to deadlocks, its initial capacity vector is decided. Then, an algorithm is proposed to compute its final capacity vector iteratively. At each iteration, the capacity of one activity place is decreased by one. The objective is to prevent the excessive occupancy of one resource by one production process, which is an important reason causing a deadlock. This process is carried out until the net model becomes live. With the constraints by the final capacity vector, the controlled net is live. It is proved the iterative algorithm is convergent. Considering the redundancy of capacity restrictions, another algorithm is given to eliminate it. The presented method for FMS control guarantees its live operation and high performance in terms of resource utilization. Generally, the proposed method is applicable, easy to use, effective and straightforward. Finally, two parameterized examples are used to demonstrate the applicability and effectiveness of the proposed approach.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 40
    facet.materialart.
    Unknown
    H∞ control for a class of non-linear discrete-time networked systems with limited information (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, the problems of stabilization and H∞ control are investigated for a class of non-linear networked systems with packet dropouts, network-induced delays and sensor faults. We construct a novel model by taking packet dropouts, distributed delays and sensor faults into account in a unified way. The packet dropouts process is modelled as a Markov chain taking values in a finite state space. Network-induced delays with distributed characteristics are divided into two intervals satisfying the Bernoulli random distribution. Sensor faults are described as stochastic variables and each sensor has different fault rate and independent of others. The resulting closed-loop system is converted into a Markov switching system. A mode-dependent controller is designed such that the closed-loop system is stochastically stable and satisfies H∞ disturbance attenuation level in terms of certain linear matrix inequalities. Finally, a numerical example is given to illustrate the usefulness of the developed method in this article.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 41
    facet.materialart.
    Unknown
    Graphs, spanning trees and divergence-free finite elements in domains of general topology (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We construct sets of basis functions of the space of divergence-free finite elements of Raviart–Thomas type in domains of general topology. Two different methods are presented: one using a suitable selection of the curls of Nédélec finite elements, the other based on an efficient algebraic procedure. The first approach looks to be more useful for numerical approximation, as the basis functions have a localized support.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 42
    facet.materialart.
    Unknown
    Does ethnic segregation matter for spatial inequality? (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The article examines the link between ethnic segregation and spatial inequality in 71 countries with different levels of economic development. The results reveal that ethnic segregation is associated with significantly higher levels of spatial inequality. This finding is not affected by the inclusion of various covariates that may influence both spatial inequality and the geographical distribution of ethnic groups, and is confirmed by a number of robustness tests. The results also suggest that political decentralisation and government quality could act as transmission channels linking ethnic segregation and spatial inequality.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 43
    facet.materialart.
    Unknown
    The external cruising costs of parking (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Existing work emphasizes the importance of traffic congestion externalities, but typically ignores cruising-for-parking externalities. We estimate the marginal external cruising costs of parking—that is, the time costs that an additional parked car imposes on drivers by inducing them to cruise for parking—which is one of the main components of cruising-for-parking externalities. The level of cruising is identified by examining to what extent the car inflow rate into a parking location falls with parking occupancy level. For a commercial street in Istanbul, we demonstrate that a marginal car parking for an hour induces 3.6 other cars to cruise for parking. This translates into an external cruising cost that is in the same order of magnitude with the external traffic congestion cost created by the trip.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 44
    facet.materialart.
    Unknown
    The impact of aircraft noise on apartment prices: a differences-in-differences hedonic approach for Frankfurt, Germany (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper assesses the implicit valuation of aircraft noise by looking at changes in list offer prices for owner-occupied apartments around the airport of Frankfurt, Germany. A differences-in-differences research design permits circumvention of typical endogeneity problems in hedonic price estimations: Namely, the construction of the northwest runway in 2011 led to new aircraft noise exposure and subsequent price decreases in some southern parts of Frankfurt. The paper compares price changes in differentially affected areas around the announcement of the runway location in December 2007 and around its commissioning in October 2011. Noise changes are measured using publicly known noise projections as well as detailed noise assessment data for 2007 and 2012. The results suggest very little realization of externality costs before noise is actually apparent. Once aircraft noise came into effect, a price devaluation of around 1.7% per decibel of additional noise due to the new runway is measured.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 45
    facet.materialart.
    Unknown
    Does weak contract enforcement affect firm size? Evidence from the neighbour’s court (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Poor contract enforcement can importantly affect firms’ incentives to grow. We investigate the causal effect of the weakness of contract enforcement on average firm size across Italian municipalities, exploiting spatial discontinuities in court jurisdictions for identification. Italy provides an ideal environment for this exercise, as it displays wide variation in judicial efficiency across courts, while the allocation of municipalities to jurisdictions is a historical legacy and does not overlap with other political or economic discontinuities. Our estimates indicate that reducing the length of judicial proceedings (i.e. improving contract enforceability) by 10% at court level leads to a 2% increase in average size of local firms. The outcome on turnover growth is of the same magnitude, suggesting that the effect operates at the intensive margin.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 46
    facet.materialart.
    Unknown
    A conditional determination of the average rank of elliptic curves (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Under a hypothesis that is stronger than the Riemann Hypothesis for elliptic curve $L$-functions, we show that both average analytic and algebraic ranks of elliptic curves in families of quadratic twists are exactly $\frac {1}{2}$. As a corollary we obtain that, under this last hypothesis, the Birch and Swinnerton-Dyer Conjecture holds for almost all curves, and that asymptotically one-half have algebraic rank 0, and the remaining half 1. We also prove an analogous result in the family of all elliptic curves. The proof uses results of Katz–Sarnak and Young on the 1-level density of zeros of elliptic curve $L$-functions. In essence, we show that, under a hypothesis analogous to Montgomery's Conjecture, a density result with limited support on low-lying zeros of $L$-functions is sufficient to determine the average rank.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 47
    facet.materialart.
    Unknown
    Multiple positive solutions of parabolic systems with nonlinear, nonlocal initial conditions (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this paper, we study the existence, localization and multiplicity of positive solutions for parabolic systems with nonlocal initial conditions. In order to do this, we extend an abstract theory that was recently developed by the authors jointly with Radu Precup, related to the existence of fixed points of nonlinear operators satisfying some upper and lower bounds. Our main tool is the Granas fixed-point index theory. We also provide a nonexistence result and some examples to illustrate our theory.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 48
    facet.materialart.
    Unknown
    Uniqueness from discrete data in an inverse spectral problem for a pencil of ordinary differential operators (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We prove a pair of uniqueness theorems for an inverse problem for an ordinary differential operator pencil of second order. The uniqueness is achieved from a discrete set of data, namely, the values at the points $-n^2\ (n\in \mathbb {N})$ of (a physically appropriate generalization of) the Weyl–Titchmarsh $m$-function $m(\lambda )$ for the problem. As a corollary, we establish a uniqueness result for a physically motivated inverse problem inspired by Berry and Dennis (‘Boundary-condition-varying circle billiards and gratings: the Dirichlet singularity’, J. Phys. A: Math. Theor. 41 (2008) 135203).To achieve these results, we prove a limit-circle analogue to the limit-point $m$-function interpolation result of Rybkin and Tuan (‘A new interpolation formula for the Titchmarsh–Weyl $m$-function’, Proc. Amer. Math. Soc. 137 (2009) 4177–4185); however, our proof, using a Mittag-Leffler series representation of $m(\lambda )$, involves a rather different method from theirs, circumventing the $A$-amplitude representation of Simon (‘A new approach to inverse spectral theory, I. Fundamental formalism’, Ann. Math. $(2)$ 150 (1999) 1029–1057). Uniqueness of the potential then follows by appeal to a Borg–Marčenko argument.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 49
    facet.materialart.
    Unknown
    Legendrian contact homology in the product of a punctured Riemann surface and the real line (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We give a combinatorial description of the Legendrian differential graded algebra associated to a Legendrian knot in $P\times {\mathbb R}$, where $P$ is a punctured Riemann surface. As an application we show that, for any integer $k$ and any homology class $h\in H_1(P\times {\mathbb R})$, there are $k$ Legendrian knots, all representing $h$, which are pairwise smoothly isotopic through a formal Legendrian isotopy, but which lie in mutually distinct Legendrian isotopy classes.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 50
    facet.materialart.
    Unknown
    The augmented marking complex of a surface (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We build an augmentation of the Masur–Minsky marking complex by Groves-Manning combinatorial horoballs to obtain a graph we call the augmented marking complex , $\mathcal {AM}(S)$. Adapting work of Masur–Minsky, we show that this augmented marking complex is quasiisometric to Teichmüller space with the Teichmüller metric. A similar construction was independently discovered by Eskin–Masur–Rafi. We also completely integrate the Masur–Minsky hierarchy machinery to $\mathcal {AM}(S)$ to build flexible families of uniform quasigeodesics in Teichmüller space. As an application, we give a new proof of Rafi's distance formula for $\mathcal {T}(S)$ with the Teichmüller metric. We have included an appendix, in which we prove a number of facts about hierarchies that we hope will be of independent interest.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 51
    facet.materialart.
    Unknown
    Mean value estimates for Weyl sums in two dimensions (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We use decoupling theory to estimate the number of solutions for quadratic and cubic Parsell–Vinogradov systems in two dimensions.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 52
    facet.materialart.
    Unknown
    From isolated subgroups to generic permutation representations (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Let $G$ be a countable group, ${\rm Sub}(G)$ be the (compact, metric) space of all subgroups of $G$ with the Chabauty topology and ${\rm Is}(G) \subseteq {\rm Sub}(G)$ be the collection of isolated points. We denote by $X!$ the (Polish) group of all permutations of a countable set $X$. Then the following properties are equivalent: (i) ${\rm Is}(G)$ is dense in ${\rm Sub}(G)$; (ii) $G$ admits a ‘generic permutation representation’. Namely, there exists some $\tau ^* \in {\rm Hom}(G,X!)$ such that the collection of permutation representations $\{\varphi \in {\rm Hom}(G,X!) \,|\, \varphi \ {\hbox {is permutation isomorphic to}}\ \tau ^*\}$ is co-meager in ${\rm Hom}(G,X!)$. We call groups satisfying these properties solitary . Examples of solitary groups include finitely generated locally extended residually finite groups and groups with countably many subgroups.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 53
    facet.materialart.
    Unknown
    Geometrically and diagrammatically maximal knots (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The ratio of volume to crossing number of a hyperbolic knot is known to be bounded above by the volume of a regular ideal octahedron, and a similar bound is conjectured for the knot determinant per crossing. We investigate a natural question motivated by these bounds: For which knots are these ratios nearly maximal? We show that many families of alternating knots and links simultaneously maximize both ratios.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 54
    facet.materialart.
    Unknown
    Local cohomology with support in ideals of symmetric minors and Pfaffians (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We compute the local cohomology modules $\mathcal {H}_Y^{\bullet }(X,\mathcal {O}_X)$ in the case when $X$ is the complex vector space of $n\times n$ symmetric (respectively, skew-symmetric matrices) and $Y$ is the closure of the $\hbox {GL}$-orbit consisting of matrices of any fixed rank, for the natural action of the general linear group $\hbox {GL}$ on $X$. We describe the $\mathcal {D}$-module composition factors of the local cohomology modules, and compute their multiplicities explicitly in terms of generalized binomial coefficients. One consequence of our work is a formula for the cohomological dimension of ideals of even minors of a generic symmetric matrix: in the case of odd minors, this was obtained by Barile in the 1990s. Another consequence of our work is that we obtain a description of the decomposition into irreducible $\hbox {GL}$-representations of the local cohomology modules (the analogous problem in the case when $X$ is the vector space of $m\times n$ matrices was treated in earlier work of the authors).
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 55
    facet.materialart.
    Unknown
    Orthogonal polynomials, reproducing kernels, and zeros of optimal approximants (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We study connections between orthogonal polynomials, reproducing kernel functions, and polynomials $p$ minimizing Dirichlet-type norms $\|pf-1\|_{\alpha }$ for a given function $f$. For $\alpha \in [0,1]$ (which includes the Hardy and Dirichlet spaces of the disk) and general $f$, we show that such extremal polynomials are non-vanishing in the closed unit disk. For negative $\alpha $, the weighted Bergman space case, the extremal polynomials are non-vanishing on a disk of strictly smaller radius, and zeros can move inside the unit disk. We also explain how $\mathrm {dist}_{D_{\alpha }}(1,f\cdot \mathcal {P}_n)$, where $\mathcal {P}_n$ is the space of polynomials of degree at most $n$, can be expressed in terms of quantities associated with orthogonal polynomials and kernels, and we discuss methods for computing the quantities in question.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 56
    facet.materialart.
    Unknown
    Does the use of risk assessments in sentences respect the right to due process? A critical analysis of the Wisconsin v. Loomis ruling (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: On 13 July 2016, the Supreme Court of Wisconsin published a crucial decision which ruled for the first time ever about the constitutionality of using algorithms in sentencing. The ruling accepted their use, arguing that defendants’ right to due process was not violated by the mere fact that they could not gain access to an adequate explanation of the algorithm. To support this position, the Court stated that the accuracy of the tools and the capacity of the judges to understand their possible malfunctioning were enough to ensure the defendants’ rights. This article criticizes this ruling by unveiling the contradictions and misunderstandings involved in the rationale embedded in the sentence. As a consequence, it advocates the use of open source algorithms in our justice systems or, at least, in sentencing.
    Print ISSN: 1470-8396
    Electronic ISSN: 1470-840X
    Topics: Mathematics , Law
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 57
    facet.materialart.
    Unknown
    Determining the base rate for guilt (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: A Bayesian assessment of the probability that the defendant in a criminal trial is guilty depends on the presumed base rate for guilt and the estimated likelihoods of the evidence. This article explores how the base rate shall be determined. Bayesian scholars have recommended a base rate of 1/ N , where N is the number of ‘possible perpetrators’, but it is unclear how the reference class of possible perpetrators shall be defined. Several solutions are explored, and it is demonstrated that each solution leads to serious sacrifices in some fundamental principle of criminal justice. Some solutions lead to arbitrary assessments, or assessments that deviate from the facts. Other solutions fail to uphold an acceptable ratio between wrongful acquittals and wrongful convictions.
    Print ISSN: 1470-8396
    Electronic ISSN: 1470-840X
    Topics: Mathematics , Law
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 58
    facet.materialart.
    Unknown
    The four regions in settlement space: a game-theoretical approach to investment treaty arbitration. Part II: cases (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Following from Part I of this article, which introduced the notion of decision-modelling for investor–state arbitration, Part II of the article uses the game theoretic notions developed in Part I to explore the question of why a relatively large fraction of investor–state disputes proceed to arbitration tribunals. Likely explanations are advanced. The detailed mathematical model derived in Part I of the article is then used to analyse 31 cases where an investor–state dispute has been judged by an arbitration tribunal. Auxiliary mathematics are developed to identify the relevant averages and variances, which are then calculated from the full data set. Three sample cases are analysed in greater detail, with the model results being compared against the actual awards. It is concluded that applying the mathematical model of the international arbitration process developed in Part I together with the data analysis laid out in Part II will provide useful insight and guidance to both parties involved or likely to be involved in a dispute between investor and state.
    Print ISSN: 1470-8396
    Electronic ISSN: 1470-840X
    Topics: Mathematics , Law
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 59
    facet.materialart.
    Unknown
    Some structural properties of quasi-degrees (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We study the structural properties of $Q$-degrees and prove that every non-computable c.e. $Q$-degree contains a perfect set. Using this result and Batyrshin’s theorem [ 4 ] we have that there is a non-computable c.e. $Q$-degree containing a single c.e. $1$-degree. We show that if $K$ is a creative set, then there is a $\Sigma^0_2\setminus\Delta^0_2$ set $B$ which is $Q$-incomparable with $K$ and for all c.e. sets $W$, if $W\leq_{Q} B$ then $W\leq_{Q}\varnothing$.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 60
    facet.materialart.
    Unknown
    Proof systems for BAT consequence relations (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: An ongoing debate about the differences between formal provability in an axiomatic system and informal provability of mathematical claims in mathematics as a whole resulted in the construction of various logics whose main purpose is to capture the inferential behaviour of the notion of informal provability, just as multiple logics of formal provability capture the behaviour of the concept of formal provability. Known logics of informal provability, based on classical logic, are unable to incorporate all intuitive principles of informal provability (most notably, reflection, which says that whatever is provable is true). One solution to this problem is to treat informal provability as an operator (Shapiro, 1985, North Holland; Reinhardt, 1986, J. Philos. Log. , 15 , 427–74; Koellner, 2016, Oxford University Press). Another solution is to weaken some of the intuitively adequate principles (Horsten, 2002, Hansel-Hohenhausen). Recently, in yet another approach to the issue, two three-valued non-deterministic logics of informal provability have been developed (Pawlowski and R. Urbaniak, 2016, Rev. Symbo. Log. ) to overcome this difficulty. Alas, the logics have been characterized semantically and no proof systems for them are available. The purpose of this article is to define tree-like proof systems for those logics and to prove the corresponding soundness and completeness theorems.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 61
    facet.materialart.
    Unknown
    A comparison of classification strategies in rule-based classifiers (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This article discusses classification strategies in rule-based classifiers, reveals how often induced rules did not lead to unambiguous classification and emphasizes a major role that classification strategies play in classification of unknown examples. Five selected popular classification strategies proposed by Michalski $et al$, Grzymała-Busse and Zou, An, Stefanowski, Sulzmann and Fürnkranz are reviewed and compared experimentally. Additionally, a new strategy that exploits $\chi^{2}$ statistic to measure the association between the rule coverage and the indicated class is proposed. The experiment was conducted on 30 UCI datasets using MODLEM and modified RIPPER classifiers.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 62
    facet.materialart.
    Unknown
    Propositional superposition logic (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We extend classical Propositional Logic (PL) by adding a new primitive binary connective $\varphi|\psi$, intended to represent the ‘superposition’ of sentences $\varphi$ and $\psi$, an operation motivated by the corresponding notion of quantum mechanics, but not intended to capture all aspects of the latter as they appear in physics. To interpret the new connective, we extend the classical Boolean semantics by employing models of the form $\langle M,f\rangle$, where $M$ is an ordinary two-valued assignment for the sentences of PL and $f$ is a choice function for all pairs of classical sentences. In the new semantics $\varphi|\psi$ is strictly interpolated between $\varphi\wedge\psi$ and $\varphi\vee\psi$. By imposing several constraints on the choice functions, we obtain corresponding notions of logical consequence relations and corresponding systems of tautologies, with respect to which $|$ satisfies some natural algebraic properties such as associativity, closedness under logical equivalence and distributivity over its dual connective. Thus various systems of Propositional Superposition Logic (PLS) arise as extensions of PL. Axiomatizations for these systems of tautologies are presented and soundness is shown for all of them. Completeness is proved for the weakest of these systems. For the other systems completeness holds if and only if every consistent set of sentences is extendible to a consistent and complete one, a condition whose truth is closely related to the validity of the deduction theorem.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 63
    facet.materialart.
    Unknown
    On Kalman’s functor for bounded hemi-implicative semilattices and hemi-implicative lattices (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Hemi-implicative semilattices (lattices), originally defined under the name of weak implicative semilattices (lattices), were introduced by the second author of the present article. A hemi-implicative semilattice is an algebra $(H,{\wedge},{\rightarrow},1)$ of type $(2,2,0)$ such that $(H,{\wedge})$ is a meet semilattice, $1$ is the greatest element with respect to the order, $a{\rightarrow} a = 1$ for every $a\in H$ and for every $a$, $b$, $c\in H$, if $a\leq b{\rightarrow} c$ then $a{\wedge} b \leq c$. A bounded hemi-implicative semilattice is an algebra $(H,{\wedge},{\rightarrow},0,1)$ of type $(2,2,0,0)$ such that $(H,{\wedge},{\rightarrow},1)$ is a hemi-implicative semilattice and $0$ is the first element with respect to the order. A hemi-implicative lattice is an algebra $(H,{\wedge},\vee,{\rightarrow},0,1)$ of type $(2,2,2,0,0)$ such that $(H,{\wedge},\vee,0,1)$ is a bounded distributive lattice and the reduct algebra $(H,{\wedge},{\rightarrow},1)$ is a hemi-implicative semilattice. In this article, we introduce an equivalence for the categories of bounded hemi-implicative semilattices and hemi-implicative lattices, respectively, which is motivated by an old construction due J. Kalman that relates bounded distributive lattices and Kleene algebras.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 64
    facet.materialart.
    Unknown
    A decomposition-based method for solving the clustered vehicle routing problem (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we address a variant of the vehicle routing problem which occurs in real-life applications, called the clustered vehicle routing problem. The clustered vehicle routing problem (CluVRP) looks for an optimal collection of routes, with respect to cost minimization, for a fleet of vehicles, fulfilling all customers’ requirements which have a particular structure being divided into clusters, the capacity constraints of the vehicles and with the additional constraint that all the customers belonging to the same cluster must be visited consecutively before leaving the cluster. We propose a novel approach for solving the problem using a decomposition-based method which splits the CluVRP into two easier subproblems. The results of the computational experiments on three sets of benchmark instances from the literature show that our approach is competitive in comparison with the known solution approaches published to date.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 65
    facet.materialart.
    Unknown
    On the structure theory of Łukasiewicz near semirings (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In a previous article by two of the present authors and S. Bonzio, Łukasiewicz near semirings were introduced and it was proven that basic algebras can be represented (precisely, are term equivalent to) as near semirings. In the same work it has been shown that the variety of Łukasiewicz near semirings is congruence regular. In other words, every congruence is uniquely determined by its 0-coset. Thus, it seems natural to wonder whether it could be possible to provide a set-theoretical characterization of these cosets. This article addresses this question and shows that kernels can be neatly described in terms of two simple conditions. As an application, we obtain a concise characterization of ideals in Łukasiewicz semirings. Finally, we close this article with a rather general Cantor–Bernstein type theorem for the variety of involutive idempotent integral near semirings.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 66
    facet.materialart.
    Unknown
    Automatic proof generation in an axiomatic system for $\mathsf{CPL}$ by means of the method of Socratic proofs (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The aim of this article is to describe an algorithm for the automatic generation of proofs in an axiomatic system for Classical Propositional Logic. The idea of the algorithm was taken from a book by Helena Rasiowa and Roman Sikorski [ 31 ], where the authors suggest using the method of diagrams to automatically obtain proofs in Classical Propositional Logic. However, in this article the method of diagrams developed by Rasiowa and Sikorski was replaced by a right-sided erotetic calculus developed by Andrzej Wiśniewski. Erotetic calculi have been used before in designing similar algorithms. The proofs are presented together with the estimations of their lengths, widths and sizes — measures introduced for the purposes of the article. The estimations are then used to derive the conclusion that the axiomatic system simulates polynomially the erotetic calculus.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 67
    facet.materialart.
    Unknown
    The quantum logic of direct-sumdecompositions: the dual to the quantum logic of subspaces (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Since the pioneering work of Birkhoff and von Neumann, quantum logic has been interpreted as the logic of (closed) subspaces of a Hilbert space. There is a progression from the usual Boolean logic of subsets to the ‘quantum logic’ of subspaces of a general vector space—which is then specialized to the closed subspaces of a Hilbert space. But there is a ‘dual’ progression. The set notion of a partition (or quotient set or equivalence relation) is dual (in a category-theoretic sense) to the notion of a subset. Hence the Boolean logic of subsets has a dual logic of partitions. Then the dual progression is from that logic of set partitions to the quantum logic of direct-sum decompositions (i.e. the vector space version of a set partition) of a general vector space—which can then be specialized to the direct-sum decompositions of a Hilbert space. This allows the quantum logic of direct-sum decompositions to express measurement by any self-adjoint operators. The quantum logic of direct-sum decompositions is dual to the usual quantum logic of subspaces in the same sense that the logic of partitions is dual to the usual Boolean logic of subsets.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 68
    facet.materialart.
    Unknown
    Books of Essays: Sébastien Gandon and Ivahn Smadja, eds. Philosophie de Mathématiques: Logique, Preuve et Pratiques. (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: GandonSébastien and Smadja,Ivahn eds. Philosophie de Mathématiques: Logique, Preuve et Pratiques. Textes clés. Jean Fichot, Brice Halimi, Baptiste Mélès, Jean-Baptiste Rauzy, Ivahn Smadja, trans. Paris: Vrin, 2017. ISBN 978-2-7116-2654-0 (pbk). Pp. 383.
    Print ISSN: 0031-8019
    Electronic ISSN: 1744-6406
    Topics: Mathematics , Philosophy
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 69
    facet.materialart.
    Unknown
    Proof and the Virtues of Shared Enquiry† (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: ABSTRACT This paper investigates an important aspect of mathematical practice: that proof is required for a finished piece of mathematics. If follows that non-deductive arguments — however convincing — are never sufficient. I explore four aspects of mathematical research that have facilitated the impressive success of the discipline. These I call the ‘Practical Virtues’: Permanence, Reliability, Autonomy, and Consensus (PRAC). I then argue that permitting results to become established on the basis of non-deductive evidence alone would lead to their deterioration (with some possible exceptions). This furnishes us with a partial rational justification for mathematicians’ strict insistence on proof.
    Print ISSN: 0031-8019
    Electronic ISSN: 1744-6406
    Topics: Mathematics , Philosophy
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 70
    facet.materialart.
    Unknown
    On coarse embeddings into c0(Γ) (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Let λ be a large enough cardinal number (assuming the Generalized Continuum Hypothesis it suffices to let λ=ℵω). If X is a Banach space with dens(X)≥λ, which admits a coarse (or uniform) embedding into any c0(Γ), then X fails to have non-trivial cotype, i.e. X contains ℓ∞n C -uniformly for every C〉1. In the special case when X has a symmetric basis, we may even conclude that it is linearly isomorphic with c0(densX).
    Print ISSN: 0033-5606
    Electronic ISSN: 1464-3847
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 71
    facet.materialart.
    Unknown
    A sharp signature bound for positive four-braids (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We provide the optimal linear bound for the signature of positive four-braids in terms of the three-genus of their closures. As a consequence, we improve previously known linear bounds for the signature in terms of the first Betti number for all positive braid links. We obtain our results by combining bounds for positive three-braids with Gordon and Litherland’s approach to signature via unoriented surfaces and their Goeritz forms. Examples of families of positive four-braids for which the bounds are sharp are provided.
    Print ISSN: 0033-5606
    Electronic ISSN: 1464-3847
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 72
    facet.materialart.
    Unknown
    Second-Order deformations of associative submanifolds in nearly parallel G2-manifolds (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Associative submanifolds A in nearly parallel G 2 -manifolds Y are minimal 3-submanifolds in spin 7-manifolds with a real Killing spinor. The Riemannian cone over Y has the holonomy group contained in Spin(7) and the Riemannian cone over A is a Cayley submanifold.Infinitesimal deformations of associative submanifolds were considered by the author. This paper is a continuation of the work. We give a necessary and sufficient condition for an infinitesimal associative deformation to be integrable (unobstructed) to second order explicitly. As an application, we show that the infinitesimal deformations of a homogeneous associative submanifold in the 7-sphere given by Lotay, which he called A 3 , are unobstructed to second order.
    Print ISSN: 0033-5606
    Electronic ISSN: 1464-3847
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 73
    facet.materialart.
    Unknown
    Understanding students’ hierarchical thinking: a view from continuity, differentiability and integrability (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This report examines how students link continuity, differentiability and integrability concepts in their mind maps within the context of hierarchical thinking. A survey research design was used to obtain a large group of participants from three different mathematics departments in Turkey. While primary data acquired with the help of the concept map were analysed using descriptive statistics, secondary data acquired by way of interviews were analysed according to their content. The findings revealed that a great majority of the participants built wrong hierarchies between these concepts. The results also show that the students’ epistemological beliefs, or their sequential learning and instrumental understanding instead of relational understanding, hinder building correct hierarchies, and some suggestions show lecturers how to effectively use concept maps and counterexamples.
    Print ISSN: 0268-3679
    Electronic ISSN: 1471-6976
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 74
    facet.materialart.
    Unknown
    Making the point: the place of gesture and annotation in teaching STEM subjects using pen-enabled Tablet PCs (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The teaching of STEM subjects, and engineering and mathematics in particular, involves the use of a wide range of representational forms, including equations, diagrams, sketches and graphs, supported by speech and gestures. In the traditional face-to-face ‘board’ based classroom, the integration of writing, speech and gesture has been a key feature of pedagogical delivery approaches. The pen-enabled Tablet PC (penTPC), used in conjunction with a data projector, allows for the maintenance of a handwritten approach in teaching environments where traditional boards are unavailable or limited. However, it has been suggested that the use of the digital interface imposes restrictions on lecturer movement and gesture, compared to traditional board environments. This article examines the adaptations made by lecturers in using the penTPC in a classroom environment. The study suggests that the use of penTPC technology does not preclude the use of gesture, and that the augmented capability for annotation in conjunction with other digital representations can enhance teaching, particularly of STEM-based discipline subjects.
    Print ISSN: 0268-3679
    Electronic ISSN: 1471-6976
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 75
    facet.materialart.
    Unknown
    The (literally) steepest slope: spatial, temporal, and elevation variance gradients in urban spatial modelling (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-14
    Description: This paper presents an analysis of elevation gradient and temporal future-station effects in urban real estate markets. Using a novel dataset from the Hong Kong publicly constructed housing sector, we find enormous housing price effects caused by levels of terrain incline between apartments and subway stations. Ceteris paribus , two similar apartments with closest metro stations of the same walking distance may sell at a difference of up to 20% because of differences in the apartment-station slope alone. Anticipatory effects are similarly robust: apartment buyers regard a future, closer metro station as being 60% present when making purchases 2 years prior to its opening.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 76
    facet.materialart.
    Unknown
    From periphery to core: measuring agglomeration effects using high-speed rail (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-14
    Description: We analyze the economic impact of the German high-speed rail (HSR) connecting Cologne and Frankfurt, which provides plausibly exogenous variation in access to surrounding economic mass. We find a causal effect of about 8.5% on average of the HSR on the GDP of three counties with intermediate stops. We make further use of the variation in bilateral transport costs between all counties in our study area induced by the HSR to identify the strength and spatial scope of agglomeration forces. Our most careful estimate points to an elasticity of output with respect to market potential of 12.5%. The strength of the spillover declines by 50% every 30 min of travel time, diminishing to 1% after about 200 min. Our results further imply an elasticity of per-worker output with respect to economic density of 3.8%, although the effects seem driven by worker and firm selection.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 77
    facet.materialart.
    Unknown
    Reinforced gradient-type iterative learning control for discrete linear time-invariant systems with parameters uncertainties and external noises (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, a reinforced gradient-type iterative learning control algorithm is developed for a type of discrete linear time-invariant systems with parameters uncertainties and external noises. The technique is to construct a symmetric learning gain matrix on basis of the system Markov parameters and an appropriate learning step length. First, for the case when both the model uncertainties and the external noises are absent, sufficient and necessary monotone convergences of the proposed algorithm are derived by means of matrix theory and norm inequality under the assumption that the learning step length is properly chosen. Then, for the cases when the model uncertainties are tolerable and the external noises are bounded, the robust monotone convergence and robustness are respectively analysed. Compared with the conventional gradient-type iterative learning control scheme, the proposed reinforced one is more efficient in speeding up the convergent tracking performance and resisting perturbations. Numerical simulations testify the validity and the effectiveness as well as the feasibility.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 78
    facet.materialart.
    Unknown
    On the Euler–Maruyama approximation for one-dimensional stochastic differential equations with irregular coefficients (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We study the strong rates of the Euler–Maruyama approximation for one-dimensional stochastic differential equations whose drift coefficient may be neither continuous nor one-sided Lipschitz and whose diffusion coefficient is Hölder continuous. In particular, we show that the strong rate of the Euler–Maruyama approximation is 1/2 for a large class of equations whose drift is not continuous. We also provide the strong rate for equations whose drift is Hölder continuous and diffusion is nonconstant.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 79
    facet.materialart.
    Unknown
    Finite element semidiscretization of a pressure–stress formulation for the time-domain fluid–structure interaction problem (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We present a convergence analysis for the space discretization via a dual-mixed formulation of a time-dependent system of partial differential equations modeling an elastoacoustic interaction problem. The resulting unknowns are given by the stress tensor in the solid and the pressure in the fluid, so that the Arnold–Falk–Winther mixed finite element method with weak symmetry in the structure and the usual Lagrange finite element method in the acoustic medium are employed to define the associated semidiscretization. We analyse the resulting global semidiscrete scheme by introducing here for the first time an adequate projector and its discrete counterpart and by estimating the error between them. We show that the method is stable uniformly with respect to the space discretization parameter and the Poisson modulus, and derive the corresponding asymptotic error estimates. In addition, our approach allows the postprocessing of the displacement and the velocity with analog convergence results.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 80
    facet.materialart.
    Unknown
    Computation of pseudospectral abscissa for large-scale nonlinear eigenvalue problems (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We present an algorithm to compute the pseudospectral abscissa for a nonlinear eigenvalue problem. The algorithm relies on global under-estimator and over-estimator functions for the eigenvalue and singular value functions involved. These global models follow from eigenvalue perturbation theory. The algorithm has three particular features. First, it converges to the globally rightmost point of the pseudospectrum, and it is immune to nonsmoothness. The global convergence assertion is under the assumption that a global lower bound is available for the second derivative of a singular value function depending on one parameter. It may not be easy to deduce such a lower bound analytically, but assigning large negative values works robustly in practice. Second, it is applicable to large-scale problems since the dominant cost per iteration stems from computing the smallest singular value and associated singular vectors, for which efficient iterative solvers can be used. Furthermore, a significant increase in computational efficiency can be obtained by subspace acceleration, that is, by restricting the domains of the linear maps associated with the matrices involved to small but suitable subspaces, and solving the resulting reduced problems. Occasional restarts of these subspaces further enhance the efficiency for large-scale problems. Finally, in contrast to existing iterative approaches based on constructing low-rank perturbations and rightmost eigenvalue computations, the algorithm relies on computing only singular values of complex matrices. Hence, the algorithm does not require solutions of nonlinear eigenvalue problems, thereby further increasing efficiency and reliability. This work is accompanied by a robust implementation of the algorithm that is publicly available.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 81
    facet.materialart.
    Unknown
    The cross-motion invariant group and its application to kinematics (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This article presents the cross-motion invariant group— CMI (3)—whose group operation is defined over unit dual quaternions such that rigid motions are cross-motion invariant; that is, the resultant translation does not depend on rotation and vice-versa. We present the main properties of CMI (3) and the differences between this group and the standard group $\text{Spin}(3)\ltimes\mathbb{R}^{3}$ of unit dual quaternions, as well as the kinematic equations under a sequence of CMI (3) operations. Two numerical examples are presented in order to illustrate the main characteristics of CMI (3).
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 82
    facet.materialart.
    Unknown
    Stability and L1-gain control for positive impulsive switched systems with mixed time-varying delays (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This article addresses the problems of exponential stability and L1-gain control for a class of positive impulsive switched systems with mixed time-varying delays. A new class of hybrid systems, called positive impulsive delayed switched systems, are introduced for the first time. A necessary and sufficient condition for the positivity of such kind of systems is proposed. Moreover, by using the average dwell time approach and the co-positive Lyapunov–Krasovskii function technique, a sufficient condition is presented to ensure the exponential stability with $L_1$-gain performance of the positive impulsive delayed switched system. Based on the obtained results, a sufficient condition for the existence of a desired state feedback controller is derived, and an iterative convex optimization approach is developed to compute the controller gain matrices. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed method.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 83
    facet.materialart.
    Unknown
    Two-level additive Schwarz methods for discontinuous Galerkin approximations of second-order elliptic problems (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We present some two-level nonoverlapping (NOV) and overlapping (OV) additive Schwarz methods for symmetric interior penalty discontinuous Galerkin methods for solving second-order elliptic problems. In particular, we investigate the influence of the penalty terms as well as the choice of coarse mesh spaces on the condition numbers of the preconditioned linear systems. Whereas the condition number estimates are aligned with the known results of ${\mathscr O}(\frac{H}{h})$ for the NOV methods and ${\mathscr O}(\frac{H}{\delta})$ for the OV methods, we identify significant differences between the two methods as far as dependences on the penalty terms and coarse spaces are concerned. The numerical experiments conducted are largely in agreement with the theoretical results.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 84
    facet.materialart.
    Unknown
    Lebesgue constants arising in a class of collocation methods (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Estimates are obtained for the Lebesgue constants associated with the Gauss quadrature points on $(-1, +1)$ augmented by the point $-1$ and with the Radau quadrature points on either $(-1, +1]$ or $[-1, +1)$. It is shown that the Lebesgue constants are $O(\sqrt{N})$, where $N$ is the number of quadrature points. These point sets arise in the estimation of the residual associated with recently developed orthogonal collocation schemes for optimal control problems. For problems with smooth solutions, the estimates for the Lebesgue constants can imply an exponential decay of the residual in the collocated problem as a function of the number of quadrature points.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 85
    facet.materialart.
    Unknown
    Discretising the Heston model: an analysis of the weak convergence rate (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we analyse the weak convergence rate of a discretisation scheme for the Heston model. Under mild assumptions on the smoothness of the payoff, and on the Feller index of the volatility process, respectively, we establish a weak convergence rate of order one. Moreover, under almost minimal assumptions, we obtain weak convergence without a rate. These results are accompanied by several numerical examples. Our error analysis relies on a classical technique from Talay & Tubaro (1990) , a recent regularity estimate for the Heston PDE ( Feehan & Pop, 2013 ) and Malliavin calculus.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 86
    facet.materialart.
    Unknown
    Residual-based a posteriori error estimation for the Maxwell’s eigenvalue problem (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We present an a posteriori estimator of the error in the $\mathrm{L}^2$-norm for the numerical approximation of the Maxwell’s eigenvalue problem by means of Nédélec finite elements. Our analysis is based on a Helmholtz decomposition of the error and on a superconvergence result between the $\mathrm{L}^2$-orthogonal projection of the exact eigenfunction onto the curl of the Nédélec finite element space and the eigenfunction approximation. Reliability of the a posteriori error estimator is proved up to higher order terms, and local efficiency of the error indicators is shown by using a standard bubble functions technique. The behavior of the a posteriori error estimator is illustrated on a numerical test.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 87
    facet.materialart.
    Unknown
    An adaptive space-time Newton–Galerkin approach for semilinear singularly perturbed parabolic evolution equations (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we develop an adaptive procedure for the numerical solution of semilinear parabolic problems with possible singular perturbations. Our approach combines a linearization technique using Newton’s method with an adaptive discretization—which is based on a spatial finite element method and the backward Euler time-stepping scheme—of the resulting sequence of linear problems. Upon deriving a robust a posteriori error analysis, we design a fully adaptive Newton–Galerkin time-stepping algorithm. Numerical experiments underline the robustness and reliability of the proposed approach for various examples.
    Print ISSN: 0272-4979
    Electronic ISSN: 1464-3642
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 88
    facet.materialart.
    Unknown
    Reexamining the determinants of fiscal decentralization: what is the role of geography? (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper contributes to the existing literature on the determinants of fiscal decentralization by exploring in depth the empirical relevance of physical geography as a determinant of fiscal decentralization; more geographically diverse countries show greater heterogeneity among their citizens. The theoretical framework imbeds geography into the concept of spatial decay in the provision of public services and our empirical estimation employs a panel data set for 94 countries for the period 1970–2010. Following the ‘first nature’ geography literature we construct a geographical fragmentation index based on elevation data and find that geographical fragmentation and area are significantly and positively related to fiscal decentralization. Following the ‘second nature’ geography literature we interact the geographical fragmentation index with time variant infrastructure variables, in order to test the effect that infrastructure and communications have on physical geography and fiscal decentralization. While the development of infrastructure tends to reduce the effect of physical geography on decentralization, this effect is rather small and mostly statistically insignificant.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 89
    facet.materialart.
    Unknown
    Quality of government and social capital as drivers of regional diversification in Europe (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Industrial diversification is crucial for economies to prosper. Recent studies have shown that regional economies tend to diversify into sectors that are related to those already present in the region. However, no study yet has investigated the impact of regional institutions. The objective of the article is to analyze how formal and informal institutions influence regional diversification. Studying 118 European regions in the period 2004–2012, we find evidence that institutions, and especially bridging social capital, matter for regions to diversify into new industries. Our results suggest that regional institutions relevant for diversification in regions are predominantly informal in character rather than formal, and bridging rather than bonding.
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 90
    facet.materialart.
    Unknown
    Limits to Globalization: Disruptive Geographies of Capitalist Development Eric Sheppard (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: Limits to Globalization: Disruptive Geographies of Capitalist DevelopmentSheppardEricOxford: Oxford University Press, 2016 ISBN: 9780199681167 (Hardback), 160 pp. Price £30.00
    Print ISSN: 1468-2702
    Electronic ISSN: 1468-2710
    Topics: Geography , Economics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 91
    facet.materialart.
    Unknown
    Shapely monads and analytic functors (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In this article, we give precise mathematical form to the idea of a structure whose data and axioms are faithfully represented by a graphical calculus; some prominent examples are operads, polycategories, properads, and PROPs. Building on the established presentation of such structures as algebras for monads on presheaf categories, we describe a characteristic property of the associated monads—the shapeliness of the title—which says that ‘any two operations of the same shape agree’. An important part of this work is the study of analytic functors between presheaf categories, which are a common generalization of Joyal’s analytic endofunctors on sets and of the parametric right adjoint functors on presheaf categories introduced by Diers and studied by Carboni–Johnstone, Leinster and Weber. Our shapely monads will be found among the analytic endofunctors, and may be characterized as the submonads of a universal analytic monad with ‘exactly one operation of each shape’. In fact, shapeliness also gives a way to define the data and axioms of a structure directly from its graphical calculus, by generating a free shapely monad on the basic operations of the calculus. In this article, we do this for some of the examples listed above; in future work, we intend to use this to obtain canonical notions of denotational model for graphical calculi such as Milner’s bigraphs, Lafont’s interaction nets or Girard’s multiplicative proof nets.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 92
    facet.materialart.
    Unknown
    Fuzzy approach to quantum Fredkin gate (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: In the framework of quantum computation with mixed states, we introduce a fuzzy approach to the quantum Fredkin gate. Under this perspective, we investigate the behaviour of the gate applied to factorized and non-factorized quantum states.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 93
    facet.materialart.
    Unknown
    Modal correspondence theory in the class of all Euclidean frames (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The core of this article is the modal correspondence theory in the class of all Euclidean frames. It shows that with respect to the class of all Euclidean frames, every modal formula is first-order definable and the problem of deciding the modal definability of sentences is undecidable.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 94
    facet.materialart.
    Unknown
    The universal homogeneous binary tree (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: A partial order is called semilinear if the upper bounds of each element are linearly ordered and any two elements have a common upper bound. There exists, up to isomorphism, a unique countable existentially closed semilinear order, which we denote by $(\mathbb{S}_{2};\leq )$. We study the reducts of $(\mathbb{S}_{2};\leq )$, i.e. the relational structures with domain $\mathbb{S}_{2}$, all of whose relations are first-order definable in $(\mathbb{S}_{2};\leq )$. Our main result is a classification of the model-complete cores of the reducts of $\mathbb{S}_{2}$. From this, we also obtain a classification of reducts up to first-order interdefinability, which is equivalent to a classification of all subgroups of the full symmetric group on $\mathbb{S}_{2}$ that contain the automorphism group of $(\mathbb{S}_{2};\leq )$ and are closed with respect to the pointwise convergence topology.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 95
    facet.materialart.
    Unknown
    On the computational complexity of detecting possibilistic locality (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The proofs of quantum nonlocality due to Greenberger, Horne and Zeilinger and due to Hardy are qualitatively different from that of Bell insofar as they rely only on a consideration of whether events are possible or impossible, rather than relying on specific experimental probabilities. We consider the scenario of a bipartite nonlocality experiment, in which two separated experimenters each have access to some measurements they can perform on a system. In a physical theory, some outcomes of this experiment will be labelled possible, others impossible, and an assignment of the values 0 (impossible) and 1 (possible) to these different outcomes forms a table of possibilities . Here, we consider the computational task of determining whether or not a given table of possibilities constitutes a departure from possibilistic local realism. By considering the case in which one party has access to measurements with two outcomes and the other three, it is possible to see at exactly which point this task becomes computationally difficult.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 96
    facet.materialart.
    Unknown
    Symbolic possibilistic logic: completeness and inference methods (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: This paper studies the extension of possibilistic logic to the case when weights attached to formulas are symbolic. These weights then stand for variables that lie in a totally ordered scale, and only partial knowledge is available on the relative strength of these weights in the form of inequality constraints. Reasoning in symbolic possibilistic logic means solving two problems. One is to compute symbolic expressions representing the weights of conclusions of a possibilistic knowledge base. The other problem is that of comparing the relative strength of derived weights, so as to find out if one formula is more certain than another one. Regarding the first problem, a proof of the soundness and the completeness of this logic according to the relative certainty semantics in the sense of necessity measures is provided. Based on this result, two syntactic inference methods are suggested. The first one shows how to use the notion of minimal inconsistent subsets and known techniques that compute them, so as to obtain the symbolic expression representing the necessity degree of a possibilistic formula. A second family of methods computes prime implicates and takes inspiration from the concept of assumption-based theory. It enables symbolic weights attached to consequences to be simplified in the course of their computation, taking inequality constraints into account. Finally, an algorithm is proposed to find if a consequence is more certain than another one. A comparison with the original version of symbolic possibilistic logic introduced by Benferhat and Prade in 2005 is provided.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 97
    facet.materialart.
    Unknown
    Implementing fragments of ZFC within an r.e. Universe (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: The present work addresses the question: to what extent do natural models of a sufficiently rich fragment of set theory exist? Such models, here called Friedberg models, are built as a class of sets of natural numbers together with the element-relation “$x$ is in $y$” given by $x\in A_y$, where $A_0$, $A_1$, $A_2$, $\ldots$ is a Friedberg numbering of all r.e. sets of natural numbers. A member $A_x$ of this numbering is considered to be a set in the given model iff the transitive closure of the induced membership relation starting from $x$ is well-founded. Furthermore, for all $k$, the set $B_k = \{x: A_x\mbox{ has size $k$ }\}$ must be recursive. It will be examined whether the axioms of set theory and some basic set-theoretic properties hold in such a model. Because they do not hold in full generality, comprehension and replacement need to be properly adapted. The validity of the axiom of power set depends on the Friedberg model under consideration. The other axioms hold in every Friedberg model.
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 98
    facet.materialart.
    Unknown
    Triple Massey products vanish over all fields (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We show that the absolute Galois group of any field has the vanishing triple Massey product property. Several corollaries for the structure of maximal pro-$p$-quotient of absolute Galois groups are deduced. Furthermore, the vanishing of some higher Massey products is proved.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 99
    facet.materialart.
    Unknown
    Bifurcation of solutions to the Allen–Cahn equation (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: We use Morse homology to study bifurcation of the solution sets of the Allen–Cahn Equation.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 100
    facet.materialart.
    Unknown
    Roi Wagner. Making and Breaking Mathematical Sense: Histories and Philosophies of Mathematical Practice. (2018)
    Oxford University Press
    Details
    Publication Date: 2018-03-06
    Description: WagnerRoi. Making and Breaking Mathematical Sense: Histories and Philosophies of Mathematical Practice. Princeton University Press, 2017. ISBN: 978-0-691-17171-5 (hbk); 978-1-40088378-3 (e-book). Pp. xiv + 236.
    Print ISSN: 0031-8019
    Electronic ISSN: 1744-6406
    Topics: Mathematics , Philosophy
    Published by Oxford University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...