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  • Articles  (17,834)
  • 2015-2019
  • 1990-1994  (17,834)
  • 1945-1949
  • 1991  (17,834)
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  • 2015-2019
  • 1990-1994  (17,834)
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  • 1
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3088-3093 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The three known demonstrations that there exist contextual hidden variables (HV) that reproduce quantum mechanics (the HV theories of Bohm–Bub, Wiener–Siegel, and Gudder) are shown to be special cases of a generalized Gudder's theory defined in this work. Within this scheme, a symplectic HV theory is introduced for which it is argued that it is physically more useful than Gudder's theory because it makes possible the definition of a Hamiltonian subquantum dynamical law that reproduces in a natural way the Schrödinger equation. On the other hand, the symplectic HV theory contains as concrete realizations a slightly modified theory of Bohm–Bub and the theory of Wiener and Siegel.
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  • 2
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3101-3110 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: An algebraic formalism is presented which simplifies and makes natural various arguments in the theories where some notion of "connected operator'' appears. As a first example, in this paper the case of N-body systems is considered.
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  • 3
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3094-3100 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: New properties on parabosonic and parafermionic Cusson's realizations of the Green's Anzätze are first obtained. Then paraproperties are shown to have a specific interest for our real world, where bosons and fermions have to be superposed if Nature is supersymmetric, these results being obtained on supersymmetric harmonic oscillators. In particular, from the Green–Cusson Ansätze, we construct a class of supersymmetric Hamiltonians that are more general than the ones issued from standard or spin–orbit coupling considerations. We explicitly consider the simplest (previously unknown) super-Hamiltonian constructed from paraproperties in quantum mechanics and establish its invariance Lie superalgebra.
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  • 4
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3117-3124 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The Chandler–Gibson theory of N-body scattering is used to define a new K matrix for N-body quantum scattering systems. The half-on-shell K matrix has the proper channel thresholds and may be computed using a K-matrix form of the CG equations. The on-shell K matrix is an Hermitian matrix for all energies and is related to a unitary scattering matrix via a Cayley transform. A B-spline solution method is developed and applied to a two-body and a three-body test problem. The three-body numerical calculations are within 0.5% of the exact solution both below and above the breakup threshold.
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  • 5
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3111-3116 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Properties of "mixed moments,'' 〈r μ〉l,L≡∫∞0r μuL (r)ul(r)dr of ground state wave functions ul(r) of angular momentum l are investigated. It is shown that for cases where the Laplacian of the central potential V(r) is positive (negative), 〈r μ〉l,L/Γ(μ+L+l+3) is a concave (convex) function of μ. These results are extended to other classes of potentials and inequalities relating "mixed moments'' to "standard moments'' with L=l, are derived. The latter are used to give a simpler, more comprehensive proof of convexity (concavity) properties of the ground state energies E(0,l) as functions of l. New rigorous bounds on the overlap 〈1〉l,L of two angular momentum ground states, the mean square radius and kinetic energies of ground states and the electric dipole moment for transition rates between two such states are obtained for various classes of potentials using the above "moment'' inequalities. These bounds are tested in the framework of a recent potential model description of the upsilon system.
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  • 6
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3125-3129 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: One possible formulation of mean-field approximations is in terms of coherent state path integrals. In this paper, the construction of uniform semiclassical approximation to coherent state integrals is investigated. As a specific example, the method is applied to the forced harmonic oscillator.
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  • 7
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3130-3134 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: The plasma wave equation with boundary conditions either on the light cone, or on a tangent plane to it, or on both, is studied. These problems arise in solutions to the inverse scattering problem but are of independent interest.
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  • 8
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3135-3140 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A set of 16 scalar invariants is given of the Riemann tensor which is shown to contain complete minimal sets in the Einstein–Maxwell and perfect fluid cases. All previously known sets fail to be complete in the perfect fluid case.
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  • 9
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3148-3157 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In a stationary space-time the brachistochrone problem can be formulated in two different ways, viz., to find the path of shortest travel time with prescribed specific energy from one space-point to another (i) measured in terms of proper time or (ii) measured in terms of the time coordinate distinguished by the stationarity assumption. It is shown that in the static case both brachistochrone problems can be reduced to geodesic problems of appropriate Riemannian three-metrics, in close analogy to the brachistochrone problem in a Newtonian potential. In the stationary but nonstatic case, however, this is true only for the proper time brachistochrones, whereas the coordinate time brachistochrones are influenced by a sort of Coriolis force. These results are illustrated by calculating the brachistochrones in Rindler, Schwarzschild, and Gödel space-times.
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  • 10
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3158-3161 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: In four space-time dimensions, there exists an infinite-parameter family of neighbors of Einstein's equations. The action is formulated in terms of an SO(3) vector potential. It is proven that the space-time metric can be computed from the SO(3) field strength by means of a parameter-independent formula with a clear geometrical meaning.
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  • 11
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    Journal of Mathematical Physics 32 (1991), S. 3162-3167 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: The time evolution of d mean field variables is considered for networks of N neurons whose connection matrices JN have d distinct rows. Certain assumptions are made about the large N behavior of JN, which guarantee the convergence of a free-energy density function. These assumptions are known to be satisfied, e.g., in the Hopfield model with p stored patterns, for d=2p. It is proved that in a scaling limit, where N tends to infinity and d stays fixed, the time evolution approaches that of a diffusion process in Rd. This process describes in detail, and for times up to o(N3/2) iterations, the dynamics of the mean field fluctuations near a local minimum of the free-energy density.
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  • 12
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    Journal of Mathematical Physics 32 (1991), S. 3168-3175 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The boundary of a boundary principle has been suggested by J. A. Wheeler as a realization of the austerity idea in field theories. This principle is described in three basic field theories—electrodynamics, Yang–Mills theory, and general relativity. It is demonstrated that it supplies a unified geometric interpretation of the source current in each of the three theories in terms of a generalized E. Cartan moment of rotation. The extent to which the boundary of a boundary principle represents the austerity principle is discussed. It is concluded that it works in a way analogous to thermodynamic relations and it is argued that deeper principles might be needed to comprehend the nature of austerity.
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  • 13
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 2456-2458 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Exact solutions are obtained for the anisotropic Bianchi type-I model in normal gauge for Lyra's geometry. The physical behavior of the models is examined in vacuum and in the presence of perfect fluids.
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  • 14
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 2459-2467 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Solutions of Einstein's equations are examined when a particular class of closed three-form fields is taken as a source. The choice of source is motivated by developments in particle physics indicating the possible existence of physical fields described by three-forms. After summarizing basic dynamical equations and some properties, attention is focused on two particular configurations: (1) static, spherically symmetric, self-gravitating, three-form fields; and (2) homogeneous and isotropic geometries coupled to three-forms. For the spherically symmetric case, there exists two mutually exclusive sets of effective equations, solutions which describe static, spherically symmetric, self-gravitating axion fields. For the one class of the effective equations, a two-parameter family of asymptotically flat solutions of the Einstein axion field equations have been constructed. The axionic black hole solution of Bowick et al. [Phys. Rev. Lett. 61, 2823 (1988)] is also recovered as a special case of this class. For the other set of equations, only a special solution has been constructed. Its properties and global structure are discussed at length. For the case of axions coupled to homogeneous and isotropic geometries, explicit solutions of the relevant equations have also been constructed. In particular, for the case where the hypersurfaces of homogeneity are either flat or characterized by negative curvature, a global solution is obtained. It represents an ever expanding universe originating from a spacelike curvature singularity. For the case of a closed universe, local solutions have been constructed, which in principle can be patched to yield a global solution. Nevertheless, by employing them, the singularity structure of this solution was able to be analyzed. It behaves in the same manner as the previous two cases.
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  • 15
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    Journal of Mathematical Physics 32 (1991), S. 3195-3198 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: A complete set of eigenfunctions on a two-dimensional sphere is obtained for the Dirac operator corresponding to a vortexlike Abelian potential. Then a decompactification limit is studied from the sphere to R2, in which the potential leads to a constant field configuration. The chiral anomaly is studied by using first-order perturbation theory and the crucial role played by zero modes in this context is carefully discussed.
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  • 16
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 2074-2081 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In the algebraic formulation of quantum theories, a state is often represented by a normal linear functional on some *-algebra @FA of operators on a Hilbert space, i.e., a functional of the form f(X)=Tr TX for some trace class operator X. The question is whether every strongly positive (i.e., positive on positive elements) linear functional is normal. Criteria for this statement to be true are well known in the case where @FA is a *-algebra of bounded operators (C*- or W*-algebra) or a *-algebra of unbounded operators (O*-algebra). Those results are extended to the case where @FA is a (weak) partial *-algebra of closable operators, both for linear functionals and for sesquilinear forms.
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  • 17
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    Journal of Mathematical Physics 32 (1991), S. 2106-2113 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Following ideas of Hemion, a method for deriving the complex amplitudes of quantum mechanics from physically motivated principles is presented. First, a generalized action and a universal influence function is introduced. It is postulated that the probability of a measurement outcome is given in terms of the sum of influences between alternatives that result in that outcome.
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  • 18
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    Journal of Mathematical Physics 32 (1991), S. 2128-2134 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The Lindblad master equation for the damped quantum harmonic oscillator is transformed into Fokker–Planck equations for quasiprobability distributions. A comparative study is made for the Glauber P representation, the antinormal-ordering Q representation and the Wigner W representation. It will be proven that the variances for the damped harmonic oscillator found with these representations are the same. By solving the Fokker–Planck equations in the steady state, it will be shown that the quasiprobability distributions are two-dimensional Gaussians with widths determined by the diffusion coefficients.
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  • 19
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 2167-2168 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The structure of naked singularity for a nonlinear mass function in Vaidya solutions for collapse of imploding radiation is examined here. The singularity is shown to be a scalar polynomial singularity even though RabKaKb does not diverge sufficiently fast along any singular geodesic.
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  • 20
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    Journal of Mathematical Physics 32 (1991), S. 2200-2209 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: Properties of four-dimensional theories on M(4), obtained from multidimensional pure Yang–Mills theories on E=M(4)×S/R via coset space-dimensional reduction, are discussed. Scalar potentials of the reduced theory for the case where S/R is a symmetric space are studied in detail. An explicit relation between extrema of these potentials and solutions of the multidimensional equations of motion (spontaneous compactification solutions) are established. Some quantum properties of the dimensionally reduced theory are also discussed.
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  • 21
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    Journal of Mathematical Physics 32 (1991), S. 2635-2659 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: The existence of Lie-point symmetries for a family of partial differential equations (PDEs) written in Hirota's bilinear formalism is investigated. These equations have been studied in previous publications from the point of view of the existence of multisoliton solutions and also of the Painlevé property and are either known as integrable or good candidates for integrability. For these equations, the Lie algebra of Lie-point symmetries is derived, which in some cases turns out to be an infinite-dimensional algebra.
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  • 22
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    Journal of Mathematical Physics 32 (1991), S. 2660-2665 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: Motivated by an example of Inönü and Wigner, a general procedure for the contraction of irreducible unitary representations of semisimple compact Lie algebras is given. In this situation, contractions mean generalized Inönü–Wigner contractions. In particular, this means that by a simple limiting process, one obtains representations of nonsemisimple noncompact Lie algebras. As examples, a general treatment of SO(3) is given as well as some results for SU(3).
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  • 23
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    Journal of Mathematical Physics 32 (1991), S. 2676-2678 
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    Notes: A crucial connection formula with closed-spaced critical points on the nearest critical level line is established in this paper in order to use the generalized Pokrovskii–Khalatnikov method to calculate the nontrivial behavior of the reflection coefficient for singular problems.
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  • 24
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    Journal of Mathematical Physics 32 (1991), S. 2703-2717 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: A technique to perform a convenient Change of (independent) variables in a PDE is reported, and it is used to generate C-integrable nonlinear PDEs, i.e., nonlinear PDEs solvable by an appropriate Change of variables. Several examples of such PDEs are exhibited.
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  • 25
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    Journal of Mathematical Physics 32 (1991), S. 2695-2702 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: Interacting multisoliton solutions of soliton equations are constructed using the inverse spectral transform and their asymptotics are analyzed. The Hamiltonian structure is obtained in terms of scattering data and the complete integrability of solutions of the N-wave equations with nontrivial interactions is proved.
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  • 26
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    Journal of Mathematical Physics 32 (1991), S. 2718-2721 
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    Notes: The mean free energy for a one-dimensional spin system with exponential interaction and the large-deviation probability for a one-dimensional ergodic dynamical system are found in exact Taylor expansion by computing the largest eigenvalue of the corresponding Ruelle–Araki transfer operator.
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  • 27
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    Journal of Mathematical Physics 32 (1991), S. 2679-2694 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: In this paper, a recently developed improved averaging method for periodic nonlinear systems of ordinary differential equations (ODEs) is extended to a wide class of nonperiodic ODE systems of nonlinear type. The paper presents the first systematic treatment of Nth-order averaging for nonperiodic systems of the present degree of generality. Our main results are: (i) a basic existence, uniqueness, and approximation theorem for Nth-order averaging for the latter systems, including explicit, rigorous error bounds expressed in terms of suitable order functions; (ii) a proof that our (N+1)st error estimate is smaller (o(1)) than the corresponding Nth-order estimate when the relevant perturbation parameter ε is sufficiently small (this is not obvious, since our error bounds are not generally proportional to powers of ε); (iii) a proof that (ii) holds when the exact order functions are replaced by appropriate upper bounds which are simpler to calculate in practice. For the example of a linear oscillator with time-dependent friction, it is shown that our second-order averaging estimates are generally better than those given by the approach of Sanders and Verhulst. Nth-order averaging for a large class of C∞ quasiperiodic systems is also discussed, generalizing earlier work of Perko.
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    Journal of Mathematical Physics 32 (1991), S. 1857-1860 
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    Notes: Rigidly rotating perfect fluids admitting two Killing vectors ξ (stationarity), η (axial symmetry), and a proper conformal Killing vector K are studied. The three-dimensional Lie algebra [ξ,η]=0, [ξ,K]=a4K, [η,K]=a3K, a32+a42≠0 is considered. It is shown that under these assumptions there are no space-times satisfying Einstein's field equations.
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    Journal of Mathematical Physics 32 (1991), S. 1881-1884 
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    Notes: Statistical mechanical systems with an exponential density of states are considered. The arithmetic analog of parafermions of arbitrary order is constructed and a formula for boson-parafermion equivalence is obtained using properties of the Riemann zeta function. Interactions (nontrivial mixing) among arithmetic gases using the concept of twisted convolutions are also introduced. Examples of exactly solvable models are discussed in detail.
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  • 30
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    Journal of Mathematical Physics 32 (1991), S. 1919-1920 
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    Notes: In a renormalizable field theory with one coupling constant, one may redefine the coupling in the sense of formal power series such that the β-function in the new coupling consists of the first two terms only. It is shown that this change of coupling is Borel summable if the original β-function was Borel summable.
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    Journal of Mathematical Physics 32 (1991), S. 1934-1937 
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    Notes: The geometry of the superspace provided by two arbitrary Poisson brackets of different gradings is studied. It will be shown that the group of transformations that preserve these two brackets is finite-dimensional.
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  • 32
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    Journal of Mathematical Physics 32 (1991), S. 1958-1960 
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    Notes: The effective conductivity of a two-phase two-dimensional composite with diamond-shaped tiling is considered. This analysis, based on a projection of the boundary conditions on linear combinations of solutions to the electrostatic equation that are orthonormal on the boundary, generalizes results by Keller [J. Math. Phys. 28, 2516 (1987)] and others. Numerical results are given for several conductivity ratios of the two phases and for varying obtuse angles of the tiles. Special emphasis is given to very large and very small conductivity differences, and very elongated tiles.
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  • 33
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    Journal of Mathematical Physics 32 (1991), S. 2802-2812 
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    Notes: The adiabatic hyperspherical (AH) approach to the quantum three-body problem is considered. It is proven that the AH harmonics are complete and differentiable with respect to the hyperradius for a large class of two-body potentials. For the case of short-range potentials, the scattering theory is studied in the framework of the AH approach. The asymptotics of the AH potential curves, harmonics, and coupling matrix elements are derived, as well as the structure of the three-body wave operators and, the S-matrix in the AH representation is investigated.
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    Journal of Mathematical Physics 32 (1991), S. 2813-2827 
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    Notes: It is developed, in a curved four-dimensional space-time, the quantum field theory of p-forms. In particular, from the Ward–Lichnerowicz identityG(p)a1...ap b1′... bp′;ap+G(p−1)a1...ap−1 [b1′... bp−1;bp′]=0 it is shown how to treat the complications that appear in the quantum theory of p-forms because of the phenomenon of ghosts for ghosts. In addition, the expression of the renormalized stress-energy tensor associated to a p-form for a Hadamard state in an arbitrary gravitational background is given.
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    Journal of Mathematical Physics 32 (1991), S. 1586-1590 
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    Notes: Explicit Fock spaces for massless multispinors and tensors satisfying (D'Alembertian)nΨ=0 are constructed. It is found that they carry indecomposable representations which allow Gupta–Bleuler type quantization. For symmetric tensors and odd n there is a unitary space of physical states.
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    Journal of Mathematical Physics 32 (1991), S. 1609-1611 
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    Notes: It is noted that certain reducible cyclic representations of the Poincaré group are square integrable in the sense of wavelet theory. The corresponding wavelet transform and resolution of the identity are constructed. An inversion formula for an irreducible representation is obtained by taking limits.
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    Journal of Mathematical Physics 32 (1991), S. 1638-1650 
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    Notes: For many-body spin cluster problems, dual-symmetry recoupled tensors over Liouville space provide suitable bases for a generalized torque formalism using the Sn-adapted density operator in which to discuss NMR and related techniques. The explicit structure of such tensors is considered in the context of the Cayley algebra of scalar invariants over a field, specified by the inner ki rank labels of the Tkq(kl−kn)s. The pertinence of both lexical combinatorial architectures over inner rank sets and SU2 propagative topologies in specifying the structure of dual recoupling tensors is considered in the context of the Sn partitional aspects of spin clusters. The form of Heisenberg superoperator generators whose algebra underlies the Gel'fand pattern algebra of SU(2) and SU(2)×Sn tensor bases over Liouville space is presented together with both the related s-boson algebras and a description of the associated {||2k 0〉〉} pattern sets of CF29H carrier space under the appropriate symmetry. These concepts are correlated with recent work on SU(2)×Sn induced symmetry hierarchies over Liouville spin space. The pertinence of this theoretical work to an understanding of multiquantum NMR in Liouville space formalisms is stressed in a discussion of the nature of pathways for intracluster J coupling, which also gives a valuable physical insight into the nature of coherence transfer in more general spin-1/2 systems.
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    Journal of Mathematical Physics 32 (1991), S. 1155-1158 
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    Notes: The structure of the quantum Heisenberg group is studied in the two different frameworks of the Lie algebra deformations and of the quantum matrix pseudogroups. The R-matrix connecting the two approaches, together with its classical limit r, are explicitly calculated by using the contraction technique and the problems connected with the limiting procedure discussed. Some unusual properties of the quantum enveloping Heisenberg algebra are shown.
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    Journal of Mathematical Physics 32 (1991), S. 1269-1272 
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    Notes: The properties of the maximum entropy approximate solutions to Fredholm integral equations of the second kind are discussed. It is proved that the approximate solutions exist and converge to the exact one for a wider class of problems than previously determined. The correspondence between the maximum entropy technique and the Galerkin method is established and on its basis an upper a posterior bound for a solution is found.
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    Journal of Mathematical Physics 32 (1991), S. 1287-1292 
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    Notes: Various impossibility proofs for hidden variables theories produced within the quantum logic approach are analyzed. A very general form of n-term Bell-type inequalities is given. From these inequalities a new impossibly proof for hidden variables theories able to reproduce all numerical results of quantum mechanics follows.
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    Journal of Mathematical Physics 32 (1991), S. 1301-1309 
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    Notes: By directly solving quantum Yang–Baxter equations (QYBE) in terms of the extended expansion scheme, besides the known solutions we find new family of solutions of braid group representations associated with the fundamental representations of An, Bn, Cn, and Dn.
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    Journal of Mathematical Physics 32 (1991), S. 2903-2906 
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    Notes: A necessary and sufficient condition is established for a state to converge to equilibrium in a dynamical system described as a Kolmogorov system. Because the time reversal of a state converging to equilibrium does not necessarily share this property, this opens the possibility of spontaneous breaking of time reversal symmetry.
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    Journal of Mathematical Physics 32 (1991), S. 2918-2922 
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    Notes: Some exact results for a reversible version of the d=1+1 bridge site (or single-step) deposition model are presented. Exact steady-state properties are determined directly for finite systems with various mean slopes. These show explicitly how the asymptotic growth velocity and fluctuations are quenched as the slope approaches its maximum allowed value. Next, exact hierarchial equations for the dynamics are presented. For the special case of "equilibrium growth,'' these are analyzed exactly at the pair-correlation level directly for an infinite system. This provided further insight into asymptotic scaling behavior. Finally, the above hierarchy is compared with one generated from a discrete form of the Kardar–Parisi–Zhang equations. Some differences are described.
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    Journal of Mathematical Physics 32 (1991), S. 2907-2917 
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    Notes: Of concern is a rigorous Thomas–Fermi theory of ground state electron densities for quantum mechanical systems in an external magnetic field. The energy functional takes the form E(ρ1,ρ2)=∑2i=1ci ∫R3ρi (x)5/3 dx + (1)/(2) ∫R3∫R3[ρ(x)ρ(y)/||x−y||]dx dy +∫R3V(x)ρ(x)dx +∫R3(B(x)(ρ1(x)−ρ2(x))dx; here ci is a positive constant, ρ1 [resp. ρ2] is the density of spin-up [resp. spin-down] electrons, ρ=ρ1+ρ2 is the total electron density, V is a given potential (typically a Coulomb potential describing electron–nuclear attraction), and B describes the effect of the external magnetic field. Let Ni=∫R3ρi(x)dx be the number of spin-up and spin-down electrons for i=1,2, and let N=N1+N2 be the total number of electrons. Specifying N and minimizing E(ρ1,ρ2) generally leads to a spin polarized system. For example, if B≤0 and B(large-closed-square)0, then ρ1≥ρ2 and N1〉N2. This and a number of related results are proved.
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    Journal of Mathematical Physics 32 (1991), S. 2923-2928 
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    Notes: By considering the geometrical equivalence of the radially symmetric Heisenberg ferromagnetic spin system in n-arbitrary spatial dimensions and the generalized nonlinear Schrödinger equation (GNLSE) with radial symmetry, it is shown that they possess the Painlevé property only for the (n=2) circularly (planar radially) symmetric case. For the circularly symmetric case, suitable (2×2) matrix eigenvalue equations are constructed, involving nonisospectral flows and their gauge equivalence is shown. The connection with inhomogeneous systems and, in particular, the linearly x-dependent system is pointed out. Appropriate Bäcklund transformations (BT) and explicit soliton solutions for both the spin systems and the GNLSEs are also derived.
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    Journal of Mathematical Physics 32 (1991), S. 2929-2935 
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    Notes: A Goldstone-type theorem is derived to reveal the nature of the spontaneous symmetry breaking occurring in the Overhauser model. Explicit expressions for the equilibrium states of the model are calculated. The fluctuations of the fields satisfy a central limit theorem. The limit is a new set of Fermionic fields that inherit their dynamics from the original model. In the low-temperature phase, where the order parameter does not vanish, this dynamics is nontrivial and basically shows oscillations with a frequency related to the order parameter.
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    Journal of Mathematical Physics 32 (1991), S. 109-119 
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    Notes: Hamiltonian operators and their behavior under differential substitutions are studied. Scalar Hamiltonian operators are classified up to fifth order, and it is shown that all such operators may be obtained from the first-order Gardner operator, Dx, by differential substitutions, thus proving an infinite-dimensional Darboux theorem for Hamiltonian systems of evolution equations corresponding to such operators.
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    Journal of Mathematical Physics 32 (1991), S. 106-108 
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    Notes: A recent paper by Gottlieb [J. Math. Phys. 29, 2434 (1988)] provides examples of acoustic wave equations, in various dimensions, that have nontrivial families of solutions that are progressing waves of order 1, and relates this to whether or not these equations satisfy Huygens' principle. A statement made in that paper related to Huygens' principle in one space dimension is clarified, and it is shown in this connection that, in general, the relationship between the possession of progressing wave solutions and the satisfaction of Huygens' principle is more complex than the situation described by Gottlieb. In addition, the attractive properties of progressing waves of order 1 are retained by progressing waves of any finite order, and we use this to generalize in several ways Gottlieb's results on "wake-free'' solutions of the acoustic equation in three dimensions.
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    Journal of Mathematical Physics 32 (1991), S. 2056-2062 
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    Notes: Let u be any one-soliton solution of class C3 of a single differential equation with two independent variables. Then u satisfies the immersion equations of a Dini surface. In this way, it is possible to generate all C3 one-soliton solutions of differential equations in two variables. In the discussion of a two-soliton solution, a new surface of Gaussian curvature −1 (a Joachimsthal surface of Enneper's type) has been found.
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    Journal of Mathematical Physics 32 (1991), S. 2082-2088 
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    Notes: An abstract theorem is given on essential self-adjointness of operators in infinite direct sum of Hilbert spaces and is applied to a class of Hamiltonians in nonrelativistic quantum field theory to prove their essential self-adjointness.
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    Journal of Mathematical Physics 32 (1991), S. 2099-2105 
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    Notes: As compared with axiomatic schemes based on the paths of massive point particles, a constructive approach based on the classical limit of the wave mechanics of matter fields has a particular advantage: The locally approximately plane waves do not only define matter rays, but can in addition be subject to interference measurements. These, in contrast to the free-fall experiments, are sensitive to the mass. This makes it possible to further specify the geometry of space-time. Light rays reveal a conformal structure of the space-time manifold. It will be shown that if, in addition, in each point of space-time locally approximately plane matter waves can be realized that are free and massive, the space-time is a Riemann space.
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    Journal of Mathematical Physics 32 (1991), S. 2135-2141 
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    Notes: A perturbative study of a class of nonsingular spiked harmonic oscillators defined by the Hamiltonian H=−d2/dr 2+r 2+λ/r α in the domain [0,∞] is carried out, in the two extremes of a weak coupling and a strong coupling regimes. A path has been found to connect both expansions for α near 2.
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    Journal of Mathematical Physics 32 (1991), S. 2158-2166 
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    Notes: Using a simple isomorphism between the symmetric and antisymmetric Fock space over L2(Rd) and the Wiener isomorphism, a unitary mapping U(s)AB:A(Hs)→L2R(S'R(Rd), dφsR) is constructed, yielding an isomorphism Ws,l(large-closed-square)A(Hsl)⊗A(Hsl)→L2R (SC(Rd)l,dlμsR), where Hs Sobolev space of order s, dφs Gaussian measure on the real Schwartz distributions with covariance operator (−Δ+1)s, dμs=dφs⊗dφs. Using W−1/2,4, the fields are constructed on L2(S'C(R4)4,d4μ−1/2R), yielding a functional integral representation for the two point function of the Euclidean Dirac field with a true Gaussian measure.
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    Journal of Mathematical Physics 32 (1991), S. 2186-2199 
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    Notes: The bosonization of b-c systems is studied with conformal weight λ on Riemann surfaces in which the moduli space is parametrized by the branch points (algebraic curves). Besides being interesting in itself, the problem is related to perturbative string theories and to nonfree conformal field theories on the complex plane with the insertion of certain spin fields called the twist fields. The method of λ-differentials is proposed, which allows a complete treatment of the b-c systems on algebraic curves with local Abelian monodromy group. It can be nevertheless applied also to more general algebraic curves allowing the computation of the Green's functions and shedding some light about the structure of the twist fields in the general case. The connections between our formalism and the solutions of the Riemann monodromy problem, used to find out the conformal blocks of conformal field theories, are pointed out.
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    Journal of Mathematical Physics 32 (1991), S. 2219-2223 
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    Notes: The finite temperature behavior of the scalar sector of models with U(1) and/or SU(2) gauge symmetries beyond the standard model is investigated. As the temperature decreases, complicated patterns of symmetry breaking and restoration appear in a model with U3(1) gauge symmetry. The results will be generalized to include an arbitrary number of U(1) and/or SU(2) factors, deriving expressions for the vacuum expectation values and masses of the scalar fields and the phase transition temperatures, to make contact with flipped model phenomenology.
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    Journal of Mathematical Physics 32 (1991), S. 2276-2278 
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    Notes: Two models of interacting polymers, both within Smoluchovski's theory, are considered. The first model has purely diagonal reaction rates and shows gelation. The second model has the same diagonal reaction rates but also some nondiagonal ones; the second model does not show gelation. Hence, contrary to intuition, gelation can be destroyed by an increase in the reaction rates. The example also disproves a conjecture stating that the diagonal reaction rates are the determining factor for gelation.
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    Journal of Mathematical Physics 32 (1991), S. 897-904 
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    Notes: The theory of Euclidean generalized random fields with nonlinear electromagnetic interaction is examined. A certain class of models described by the theory is given where ultraviolet divergences are mild and the field confines charges. In fact, for each model of the class, the Wilson loop can be defined without any renormalization of infinities and the static potential which is defined through the expectation value of the Wilson loop tends to infinity as the intercharge distance tends to infinity.
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    Journal of Mathematical Physics 32 (1991), S. 1709-1716 
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    Notes: The Lie algebra of symmetries of the Landau–Lifshitz equation (LL) is discussed. Point, higher-order, and nonlocal symmetries of the LL are computed. The recursion operator is constructed from a nonlocal symmetry, reflecting the bi-Hamiltonian structure of the LL. The same recursion operator of the LL has been derived by Barouch, Fokas, and Papageorgiou [J. Math. Phys. 29, 2628 (1988)], starting from the Lax pair.
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    Journal of Mathematical Physics 32 (1991), S. 1737-1743 
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    Notes: Using the special Riemann-problem technique of Zakharov et al. [Sov. Phys. JETP 47, 1017 (1978)], an explicit N-step Bäcklund transformation is derived for a class of 1+1-dimensional nonlinear evolution equations, thus providing an alternative explicit expression of their N-soliton solutions which no longer involves computations of the intermediate solutions, nor leaves any expansion of N×N determinants (and their differentiation) to be done.
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    Journal of Mathematical Physics 32 (1991), S. 1744-1749 
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    Notes: Each of the equations related to the Korteweg–de Vries (KdV) equation through a Miura transformation is described in terms of a homogeneous manifold associated to the loop group of SL(2,C)-valued maps on the circle.
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    Journal of Mathematical Physics 32 (1991), S. 959-966 
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    Notes: Time-dependent normal form theory is introduced and studied in the context of Schrödinger initial value problems associated with Hamiltonians having time-dependent perturbations to arrive at approximations that deviate in norm from the exact solution by a term of order εm+1(1+t) provided the initial vector is restricted to an appropriate dense subspace. In addition to the abstract theory within a rigorous Hilbert space formalism, it is applied to the quantum mechanical Hamiltonians of the form n harmonic oscillators coupled via an interaction of the form ε times sum of products of bounded continuous functions with polynomials in the position and momenta variables satisfying a nonresonance condition. In particular, first-order approximation is explicitly constructed for time evolution of a system describing anharmonic oscillator which changes trigonometrically with time.
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    Journal of Mathematical Physics 32 (1991), S. 19-23 
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    Notes: A representation of the SL(2,C) current algebra in terms of Hermitian currents constructed from free fields is obtained. The representation is not of the highest weight type. The restriction k≥4 on the Kac–Moody central charge k is obtained. If k=4, then the Sugawara construction defines the energy-momentum tensor equal to the energy-momentum tensor of the free-field theory.
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    Journal of Mathematical Physics 32 (1991), S. 1-7 
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    Notes: The well-known Jacobi variables in celestial mechanics are generalized to other Hamiltonian systems which include vortex dynamics. A combinatorial algorithm for constructing the generalized Jacobi variables is given; for any binary tree T(N) with N leave, there is a 2N×2N real symplectic matrix MT (T(N),Γ) which completely defines a linear canonical transformation to these relative variables. This algorithm yields a direct proof of the symplectic property for all the generalized Jacobi variables. An application to vortex dynamics is outlined here.
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    Journal of Mathematical Physics 32 (1991), S. 210-222 
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    Notes: Some consequences of duality in three dimensions is studied. In the case of pure gravity, a dual Ansatz is shown to lead to pure gauge configurations, and in a Weyl invariant gravitational theory, duality arises as an equation of motion. Its solutions obey the Liouville equation, and describe a rotating Chern–Simons fluid in a gravitational field.
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    Journal of Mathematical Physics 32 (1991), S. 231-233 
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    Notes: All exact solutions of the Einstein–Dirac field equations are given that satisfy the energy conditions and for which the spinor components of the Dirac bispinor are aligned but have different amplitude. They are all pure radiation fields of Kundt's class.
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    Journal of Mathematical Physics 32 (1991), S. 595-598 
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    Notes: In this paper, a realization of the q-deformed boson operators on the Fock space from a generally algebraic point of view is given. The representations of the quantum group (Cn)q are thereby constructed in terms of this realization. Some infinite- and finite-dimensional representations of the q-analog of the Heisenberg–Weyl algebra are obtained on certain quotient spaces. Finally, the q-deformed differential realization of quantum group given by Alvarez-Gaume, Gomez, and Sierra (Preprint CERN-Th 5369/89) is derived from the boson realization.
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    Journal of Mathematical Physics 32 (1991), S. 621-629 
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    Notes: The notion of extensions of representations of a Lie superalgebra is defined and related to associated cohomology. Sufficient conditions for triviality of an extension are given, such as: extensions of representations, having different infinitesimal characters, always split. Irreducible Harish–Chandra modules of osp(1,2), and their extensions, are constructed and classified.
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    Journal of Mathematical Physics 32 (1991), S. 630-641 
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    Notes: Generalized point interactions (GPI) appearing formally in (quantum) physics as pseudopotentials are given an operator theoretic basis. It is pointed out that in contrast to ordinary point interactions these GPI models are not self-adjoint generators in the physical Hilbert space H0, but "live'' instead in an apparently nonphysical Pontryagin space of the type Πm=H0⊕Cm(large-closed-square)Cm. The physical interpretation of the models lies in the association of a unitary S-operator on H0 within a two-space setting. A general formalism for GPI is presented and used to answer questions, which were raised in the literature, on the underlying mathematical structure of some models involving pseudopotentials in higher dimensions. Quantum mechanical scattering from GPI, with the purpose of replacing a spherically symmetric short-range interaction potential in the low-energy regime, is discussed in detail. The possible power of using GPI to enable explicit calculations in quantum mechanical and electromagnetic multiple scattering from distortions that are small relative to the wavelength is briefly mentioned.
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    Journal of Mathematical Physics 32 (1991), S. 1928-1933 
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    Notes: The strict mathematical derivation is given for the recursion relations of the coefficients of the character expansion of the single-link action in the SU(2), U(2), and SU(3) groups. This relies on the immediate Schwinger–Dyson variation on the character. It will be suggested that the independent recursion relations for the U(N) and SU(N) groups are associated with the group invariants, i.e., the Casimir invariants and the unit generator [for U(N)].
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    Journal of Mathematical Physics 32 (1991), S. 1949-1957 
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    Notes: Properties of the Euler–Lagrange differential equation for cos F, where F is the chiral angle of the classical Skyrme soliton in the hedgehog ansatz, are investigated. The power series solution for y=cos F, is obtained that presents the behavior of an almost geometric series, and the existence of single poles located at imaginary values of the radial variable r is shown. Padé approximants are built to the series expansion about the origin, and its terms are modified in order to incorporate the main features of the asymptotic behavior of the field configuration. Thus rational fractions are constructed which provide very good and practical analytical representations of the Skyrme soliton profile function.
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    Journal of Mathematical Physics 32 (1991), S. 1427-1429 
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    Notes: q-oscillator representations of the quantum superalgebra ospq(3,2) are discussed. It is pointed out that the metaplectic representation of ospq(3,2) can be equivalently realized either in terms of one q-boson and one q-fermion or with one q-boson and two q-fermions.
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    Journal of Mathematical Physics 32 (1991), S. 1437-1439 
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    Notes: Magnetohydrostatic equilibria with two relevant length scales are considered. Their ratio Ε is assumed to be small. Regular solutions in the sense of singular perturbation theory are discussed and the magnetic flux function A (2-D case) and Euler potentials α, β (3-D case) are shown that can be expanded into convergent power series in Ε. This ensures further the existence of weakly 2-D and 3-D equilibria within a bounded domain.
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    Journal of Mathematical Physics 32 (1991), S. 708-713 
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    Notes: A stationary axisymmetric type-D solution of the Einstein equations coupled with an electromagnetic field and a rigidly rotating perfect fluid distribution of finite dimensions is presented. For vanishing fluid parameters, it reduces to the Carter [A] metric, which contains among others the Kerr–Newman solution. When the electromagnetic field is switched off, it reduces to the Wahlquist perfect fluid metric. The Debever–Penrose directions are geodesic, shear-free, twisting, and diverging. This solution belongs to the Wainwright class II. The expressions of the functions of other new solutions are also given.
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    Journal of Mathematical Physics 32 (1991), S. 728-734 
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    Notes: The invariant projections of the generalized canonical, symmetric, and variational energy-momentum tensor and their divergences are investigated in spaces with affine connection and metric. Connections between the obtained quantities are found on the basis of the generalized covariant Bianchi-type identities and the covariant Euler–Lagrange equations. It can be shown that the weak principle of equivalence can be considered as a corollary of the Euler–Lagrange equations for a given field theory.
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    Journal of Mathematical Physics 32 (1991), S. 305-309 
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    Notes: An investigation of the supersymmetric reduction of the Wess–Zumino model is carried out for the subgroups of the Poincaré group. The necessary conditions for residual supersymmetry derived from super Poincaré transformations and a classification of the subalgebras of the Poincaré algebra, which might give rise to supersymmetric residual systems, are obtained. Two supersymmetric reductions of the off-shell model (with interactions) by bidimensional subgroups are presented.
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    Journal of Mathematical Physics 32 (1991), S. 50-56 
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    Notes: A quantum three-body system with zero angular momentum is considered. The plane wave F related to this problem is studied. It is proved to be a function of two variables that have a meaning of the eikonals on the internal space. A number of explicit formulas for F and its asymptotics are derived. New addition theorems for the scalar hyperspherical harmonics as well as for some special functions are obtained.
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    Journal of Mathematical Physics 32 (1991), S. 40-49 
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    Notes: This paper is concerned with the Painlevé expansion and the singularity manifold (SM) equation of the Kadomtsev–Petviashvili (KP) equation. Several aspects of the interrelation between the SM equation and the KP auxiliary linear system are studied. It is shown that the simultaneous Painlevé expansion for the KP potential u and the KP eigenfunction ψ can be treated as a Bäcklund-gauge transformation. Two methods for the derivation of the SM equation based on this treatment are proposed and their equivalence is proved. The interrelation between the SM equation and the vertical hierarchy of the KP eigenfunction equations is discussed. The explanation of the coincidence of the KP eigenfunction equation of the second level and the KP SM equation is given. Compact forms of the hierarchy of SM equations of the KP hierarchy are presented. The connection between the KP singularity manifold function cursive-phi and the KP eigenfunctions ψ and the adjoint KP eigenfunctions ψ* is derived. The bilinear-bilocal description of the hierarchy the KP SM equations is given within the framework of Sato's τ-function theory.
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    Journal of Mathematical Physics 32 (1991), S. 57-61 
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    Notes: This paper proves a previous conjecture of the author characterizing sequences h∈l2(Z) that yield orthonormal wavelet bases of L2(R) in terms of the multiplicity of the eigenvalue 1 of an operator associated to h. The proof utilizes a result of Cohen characterizing these sequences in terms of the real zeros of their Fourier transforms. The mapping from sequences to wavelets is shown to define a continuous mapping from a subset of l2(Z) into L2(R). Related conjectures are discussed.
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    Journal of Mathematical Physics 32 (1991), S. 72-74 
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    Notes: A formula that yields an (apparently—but only apparently—nontrivial) Lax pair for any nonlinear evolution PDE in 1+1 dimensions possessing a local conservation law is presented. Several examples are exhibited.
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    Journal of Mathematical Physics 32 (1991), S. 69-71 
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    Notes: The most general Kadomtsev–Petviashvili (KP) type equation, [ut+aˆ(t,x,y)u+b(t,x,y) ux+c(t,x,y)uux+d(t, x,y)uxxx]x+k(t,x,y) uyy=e(t,x,y), is studied and the conditions for the coefficients, in order that it owns complete integrability, are determined via a Painlevé test. Finally, it is proved that the above conditions are the same as those requested for reducing the equation to the canonical form via suitable transformations.
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    Journal of Mathematical Physics 32 (1991), S. 62-68 
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    Notes: An extension of Szegö's theorem, Theorem 1 in the text, is proved by using the elementary theory of complex functions and the Wiener–Lévy theorem.
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    Journal of Mathematical Physics 32 (1991), S. 75-83 
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    Notes: A systematic method for investigating the existence of nontrivial generalized Lie symmetries is presented and the associated integrals of motion for nonlinear oscillator systems with three-degrees of freedom defined in terms of the Lagrangian by L= (1)/(2) (x(overdot)2+y(overdot)2+z(overdot)2)−V(x,y,z) are constructed. Then the method is applied to study the integrability properties of quartically and cubically coupled nonlinear oscillators with three degrees of freedom. Compatibility with the Painlevé property is also investigated.
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    Journal of Mathematical Physics 32 (1991), S. 447-456 
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    Notes: A supersymmetry-inspired factorization method is used to obtain exact analytic solutions for one or a few quantum states of a broad class of nonpolynomial potentials in an arbitrary space dimension under suitable constraints on the potential parameters. For the specific nonpolynomial oscillator potential, V(x)=x2+λx2/(1+gx2), previous analytic results including algebraic and integral type in one and three dimensions are easily obtainable from these compact expressions. Interesting aspects of the existence of pairs of solutions for certain combinations of λ and g are also discussed.
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    Journal of Mathematical Physics 32 (1991), S. 466-469 
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    Notes: The degenerate Rayleigh–Schrödinger perturbation theory for the eigenvalues of the class of Schrödinger operators S(Ε)=S0+ΕV, where S0 is the Laplace–Beltrami operator on the one-dimensional torus T1 and V is an analytic potential (perturbed rotator) is explicitly constructed by means of the algorithm of the classical, resonant Birkhoff normal form. As a consequence, the (degenerate) quantum perturbation theory tends to the classical one in the classical limit.
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    Journal of Mathematical Physics 32 (1991), S. 480-484 
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    Notes: Infinitesimal Bäcklund transformations are found for the problem of classical general relativity in d dimensions, which by dimensional reduction may be interpreted as gravitation interacting with several Maxwell and scalar fields. The transformations are constructed in terms of the solution of a linear system whose integrability condition yields the original field equations. The Kac–Moody algebra, which generates those transformations, is analyzed.
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    Journal of Mathematical Physics 32 (1991), S. 500-505 
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    Notes: The Lagrangian formalism for time-dependent systems is developed using vector fields defined in the extended tangent bundle T(Q×R). The definition of the time-independent extended Lagrangian function L associated to a time-dependent Lagrangian L is given and then the techniques of symplectic mechanics are used to prove some properties of the equations determining the Euler–Lagrange vector field. The relations between the time-independent and the time-dependent Helmholtz conditions are analyzed from a geometric perspective and, finally, the Noether theorem for the extended Lagrangian L is considered.
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    Journal of Mathematical Physics 32 (1991), S. 515-523 
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    Notes: The effective action for non-Abelian gauge theories on a finite, periodic lattice is derived by imposing the static, time averaged Landau gauge. This gauge appears to be very convenient for problems in which there is one preferred direction, as in the finite temperature case.
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    Journal of Mathematical Physics 32 (1991), S. 540-543 
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    Notes: The Wess–Zumino term, in the context of the anomalous chiral Schwinger model, is derived using the Dirac formulation for constrained system. The guideline of this construction is the iterative transformation of second-class constraints into first-class ones with the addition of appropriated counter terms in the Lagrangian.
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    Journal of Mathematical Physics 32 (1991), S. 561-563 
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    Notes: Exploring cyclic permutation matrices on a space of N q-state spins, novel arithmetical polynomials in q of degree N are introduced, which satisfy interesting relations (especially congruence relations zero to modulus N. i.e., generalization to an arbitrary integer of Fermat's little theorem) and provide a natural representation of spectral properties with much physical significance.
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    Journal of Mathematical Physics 32 (1991), S. 3231-3240 
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    Notes: For each magic basis of Lie g, it is known that the Virasoro master equation on affine g contains a generalized graph theory of conformal level-families. In this paper, it is found that the superconformal master equation on affine g×SO(dim g) similarly contains a generalized graph theory of superconformal level-families for each magic basis of g. The superconformal level-families satisfy linear equations on the generalized graphs, and the first exact unitary irrational solutions of the superconformal master equation are obtained on the sine-area graphs of g=SU(n), including the simplest unitary irrational central charges c=6nx/(nx+8 sin2(rsπ/n)) yet observed in the program.
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    Journal of Mathematical Physics 32 (1991), S. 3254-3260 
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    Notes: Scattering connected with the symmetry of a system is treated. Symmetries related to Riemannian symmetric spaces of the noncompact type are studied. Several examples are discussed.
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    Journal of Mathematical Physics 32 (1991), S. 3278-3284 
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    Notes: In this paper the generalized Liouville–Green approximation is used to study the wave reflection with a turning point at infinity. The method provided here unifies the work by many authors in finding the nontrivial behavior of the reflection coefficient for high-energy particles above barrier in the semiclassical limit.
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    Journal of Mathematical Physics 32 (1991), S. 3312-3314 
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    Notes: A new method of calculating a posteriori error bounds for maximum entropy approximate solutions to Fredholm integral equations is introduced. A numerical example confirming the efficacy of the method is also presented.
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    Journal of Mathematical Physics 32 (1991), S. 3331-3332 
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    Notes: The Painlevé formulation is given for the regularized long-wave equation, which has been used to describe shallow water waves and drift waves in a plasma. The Lie group symmetries of the equation is then studied and it is shown that the only symmetries are due to the three conserved quantities.
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    Journal of Mathematical Physics 32 (1991), S. 3339-3345 
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    Notes: In a paper by Huebschmann [J. Reine Angew. Math. 408, 57 (1990)], the geometric quantization of Poisson manifolds appears as a particular case of the quantization of Poisson algebras. Here, this quantization is presented straightforwardly. The results include a geometric prequantization integrality condition and its discussion in particular cases such as Dirac brackets, an adaptation of the notion of a polarization and a construction of a quantum Hilbert space, and a computational example. In the last section of the paper the general prequantization representations in the sense of Urwin [Adv. Math. 50, 126 (1983)] are described for the Poisson and Jacobi manifolds.
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    Journal of Mathematical Physics 32 (1991), S. 3369-3375 
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    Notes: The three degrees of freedom Smorodinsky–Winternitz system is a degenerate or super-integrable Hamiltonian that possesses five functionally independent globally defined and single-valued integrals of the motion in both classical and quantum mechanics. This is explained in terms of a forced degeneracy imposed as a consequence of the invariance of the Hamiltonian under a group of symmetry transformations isomorphic to the three-dimensional unitary unimodular group, SU(3). In turn, this degeneracy group is embedded in a larger group of transformations that maps all the bound energy levels among each other, the so-called dynamical group. All the bound state eigenfunctions act as basis functions for a single irreducible representation of the dynamical group. So, in common with the hydrogen atom and the harmonic oscillator, the quantum mechanics of the Smorodinsky–Winternitz system may be completely solved within the framework of group theory alone.
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    Journal of Mathematical Physics 32 (1991), S. 3376-3380 
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    Notes: Following Ruback, the evidence for scattering at right angle of two vortices in a head-on collision is discussed. The evidence is given in terms of the approximate solutions of the equations of motion. This makes it possible to extend the analysis to the case of a small net repulsive force between the corresponding static vortex configurations. The ordinary differential equations, which result from the ansatz for the approximate solutions, are solved by Taylor series at the origin and by asymptotic series at infinity.
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    Journal of Mathematical Physics 32 (1991), S. 3412-3422 
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    Notes: The existence of Killing vectors and Killing tensors in two-dimensional space-times is discussed. The corresponding mechanical problem having a potential with two exponential terms is analyzed in detail and a number of cases admitting Killing tensors are given. The Killing tensors give rise to new exact solutions in perfect fluid Bianchi and Kantowski–Sachs cosmologies as well as in inflationary models with a scalar field source.
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    Journal of Mathematical Physics 32 (1991), S. 3439-3454 
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    Notes: Multispeed discrete Boltzmann models in Rd, satisfying all conservation laws and leading to well-defined temperatures, are studied. The (1+1)-dimensional restriction of the system of partial differential equations (PDE) satisfied by the densities of these models can be classified. One class is characterized, along a chosen coordinate, by the number and location of the independent densities and by the number and physical meaning of the independent collision terms. Each class defines a hierarchy of PDE that depends on the dimension d of a particular model in Rd. Different classes associated either with two velocity speeds 1, and 1, (d)1/2 and 2, and 2, (d)1/2 or three velocity speeds 0, 1, and 0, 2, are obtained. Each class represents a d-hierarchy of a well-known discrete model. The simplest exact solutions which are the similarity shock wave solutions are discussed and compared with the Rankine–Hugoniot solutions.
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    Journal of Mathematical Physics 32 (1991), S. 2427-2434 
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    Notes: The ordinary (holomorphic) N=2 Wess–Zumino model in supersymmetric quantum mechanics is extended to the case where the superpotential V(z) is a meromorphic function on C(large-closed-square){∞}. The extended model is analyzed in a mathematically rigorous way. Self-adjoint extensions and the essential self-adjointness of the supercharges are discussed. The supersymmetric Hamiltonian defined by one of the self-adjoint extensions of the supercharges has no fermionic zero-energy states ("vanishing theorem''). It is proven that if V(z) has only one pole at z=0 in C, then the supercharges are essentially self-adjoint on C∞0(R2(large-closed-square){0};C4). The special case where V(z)=λz−p(p∈N,λ∈C(large-closed-square){0}) is analyzed in detail to prove the following facts: (i) the number of the bosonic zero-energy ground state(s) is equal to p−1; (ii) the supercharges are not Fredholm.
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