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  • Articles  (1,148)
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  • 1
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    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 37 (1996), S. 3854-3881 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The invariant imbedding technique, via the solution of a Riccati-type equation, is modified to calculate the wave fields inside and scattered from a strongly (laterally and vertically) heterogenous, anisotropic inclusion, which may be large but remains compact. The factorization underlying this approach is carried out with respect to direction of average power flow rather than the more conventional factorization with respect to local direction of propagation. The solution of the operator Riccati equation is related to the Dirichlet-to-Neumann map. The formulation is robust in the sense that it can handle a rather extreme range of modal wave speeds, and allows continuous as well as discontinuous medium variations on different (wave) length scales. It also, inherently, takes care of critical-angle phenomena. The algorithm, based on the invariant imbedding approach, yields the internal fields for a full survey of sources and receivers simultaneously. The wave field solution in the inclusion is coupled to the external field via a boundary element approach. © 1996 American Institute of Physics.
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  • 2
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    Journal of Mathematical Physics 37 (1996), S. 3954-3972 
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    Topics: Mathematics , Physics
    Notes: In this paper we show that a quasi-exactly solvable (normalizable or periodic) one-dimensional Hamiltonian satisfying very mild conditions defines a family of weakly orthogonal polynomials which obey a three-term recursion relation. In particular, we prove that (normalizable) exactly solvable one-dimensional systems are characterized by the fact that their associated polynomials satisfy a two-term recursion relation. We study the properties of the family of weakly orthogonal polynomials defined by an arbitrary one-dimensional quasi-exactly solvable Hamiltonian, showing in particular that its associated Stieltjes measure is supported on a finite set. From this we deduce that the corresponding moment problem is determined, and that the kth moment grows like the kth power of a constant as k tends to infinity. We also show that the moments satisfy a constant coefficient linear difference equation, and that this property actually characterizes weakly orthogonal polynomial systems. © 1996 American Institute of Physics.
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  • 3
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    Journal of Mathematical Physics 37 (1996), S. 4053-4061 
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    Topics: Mathematics , Physics
    Notes: Expressions for the complete metric and vector potential perturbations of solutions of the Einstein–Maxwell equations with a null background electromagnetic field in terms of two complex scalar potentials are derived using Wald's method of adjoint operators. The perturbations of the Bell–Szekeres solution, in the regions prior to the collision of the plane-fronted waves, are obtained by this approach. We find that there exist nontrivial u-independent perturbations (where ∂u defines the direction of propagation of the colliding wave) which, when the electromagnetic perturbation vanishes, are exact solutions of the Einstein–Maxwell equations. © 1996 American Institute of Physics.
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  • 4
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    Journal of Mathematical Physics 37 (1996), S. 3933-3953 
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    Topics: Mathematics , Physics
    Notes: We discuss several aspects of second quantized scattering operators Sˆ for fermions in external time-dependent fields. We derive our results on a general, abstract level having in mind as a main application potentials of the Yang-Mills type and in various dimensions. We present a new and powerful method for proving the existence of Sˆ which is also applicable to other situations like external gravitational fields. We also give two complementary derivations of the change of phase of the scattering matrix under generalized gauge transformations which can be used whenever our method of proving the existence of Sˆ applies. The first is based on a causality argument, i.e., Sˆ (including phase) is determined from a time evolution, and the second exploits the geometry of certain infinite-dimensional group extensions associated with the second quantization of one-particle operators. As a special case we obtain a Hamiltonian derivation of the axial fermion-Yang-Mills anomaly and the Schwinger terms related to it via the descent equations, which is on the same footing and traces them back to a common root. © 1996 American Institute of Physics.
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  • 5
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    Journal of Mathematical Physics 37 (1996), S. 3354-3374 
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    Topics: Mathematics , Physics
    Notes: Description of the grand canonical Gibbs ensemble for classical continuous systems in terms of the nonlocally perturbed infinite-divisible generalized random fields is presented. The equivalence of the traditional description with the ones presented here on the level of DLR equations is established. The antiferromagnetism for the purely repulsive interactions has been observed. Finally, the usefulness of our description for an analysis of the high-temperature cluster expansion has been demonstrated. © 1996 American Institute of Physics.
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  • 6
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    Journal of Mathematical Physics 37 (1996), S. 3415-3421 
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    Topics: Mathematics , Physics
    Notes: A higher-order nonlocal evolution equation describing internal waves in a deep fluid is shown to be asymptotically integrable only if the coefficients of the higher-order terms satisfy certain constraints. In this case, the nonlocal equation can be transformed to the integrable Benjamin–Ono equation. The asymptotic integrability of the reductions of the higher-order evolution equation to a complex Burgers equation, to an envelope-wave equation, and to a finite-dimensional dynamical system is also considered. © 1996 American Institute of Physics.
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  • 7
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    Journal of Mathematical Physics 37 (1996), S. 3483-3490 
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    Topics: Mathematics , Physics
    Notes: Lie superalgebraic methods are used to establish a connection between the huge Lie superalgebra Xi of super- (pseudo-) differential operators and various super KP-hierarchies. We show in particular that Xi splits into 5=2×2+1 graded algebras expected to correspond to five classes of super-KP-hierarchies generalizing the well-known Manin–Radul and Figueroa–Mas–Ramos supersymmetric KP-hierarchies. © 1996 American Institute of Physics.
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  • 8
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    Journal of Mathematical Physics 37 (1996), S. 3539-3547 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: The massless spin 2 free-field equation is studied in the Robertson–Walker space–time via the Newman–Penrose formalism and separated by using a Chandrasekhar–Teukolski method. The resulting temporal and angular equations are explicitly integrated. The radial equations are solved in the flat universe case. The closed universe case shows, in principle, the existence of a discrete spectrum of the energy of the massless particles. In the general case of spin greater than 2 the massless field equations are shown to be separable by induction. The separated equations admit the same recurrence structure and analog interpretation properties of the spin 2 and less than 2 cases. © 1996 American Institute of Physics.
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  • 9
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    Journal of Mathematical Physics 37 (1996), S. 3522-3538 
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    Topics: Mathematics , Physics
    Notes: The perennial formalism is applied to the real, massive Klein–Gordon field on a globally-hyperbolic background space–time with compact Cauchy hypersurfaces. The parametrized form of this system is taken over from the accompanying paper. Two different algebras Scan and Sloc of elementary perennials are constructed. The elements of Scan correspond to the usual creation and annihilation operators for particle modes of the quantum field theory, whereas those of Sloc are the smeared fields. Both are shown to have the structure of a Heisenberg algebra, and the corresponding Heisenberg groups are described. Time evolution is constructed using transversal surfaces and time shifts in the phase space. Important roles are played by the transversal surfaces associated with embeddings of the Cauchy hypersurface in the space–time, and by the time shifts that are generated by space–time isometries. The automorphisms of the algebras generated by this particular type of time shift are calculated explicitly. The construction of the quantum theory using the perennial formalism is shown to be equivalent to the Segal quantization of a Weyl system if the time shift automorphisms of the algebra Scan are used. In this way, the absence of any timelike Killing vector field in the background space–time leads naturally to the "problem of time'' for quantum field theory on a background space–time. Within the perennial formalism, this problem is formally identical to the problem of time for any parametrized system, including general relativity itself. Two existing strategies—the "scattering'' approach, and the "algebraic'' approach—for dealing with this problem in quantum field theory on a background space–time are translated into the language of the perennial formalism in the hope that this may give some insight into how the general problem can be solved. The non-unitary time evolution typical of the Hawking effect is shown to be due to global properties of the corresponding phase space: specifically, the time shifts map a global transversal surface to a non-global one. Thus, the existence of this effect is closely related to the global time problem. © 1996 American Institute of Physics.
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  • 10
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    Journal of Mathematical Physics 37 (1996), S. 2569-2584 
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    Topics: Mathematics , Physics
    Notes: The most general Skyrme–Sigma models in two and three Euclidean dimensions described by O(3) and O(4) fields, respectively, are studied first by numerical methods, and analytic proofs of existence are subsequently given. Particular emphasis is given to the special cases of these models, where the topological inequalities can be saturated by self-duality equations. The O(d+1) models in d dimensions exhibit qualitatively similar features. © 1996 American Institute of Physics.
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  • 11
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    Journal of Mathematical Physics 37 (1996), S. 2637-2642 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: Sufficient conditions for the existence of the infimum AΛB of two quantum effects A and B are given. The existence of AΛB is characterized for commuting A and B with pure point spectrum. Properties of a generalized infimum and supremum are studied. Some previous finite dimensional, commutative results are extended to the infinite dimensional and noncommutative case. © 1996 American Institute of Physics.
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  • 12
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    Journal of Mathematical Physics 37 (1996), S. 2674-2681 
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    Topics: Mathematics , Physics
    Notes: We derive a general expression for the transformation brackets between the chains U(ν+1)&supuline;U(ν)&supuline;SO(ν) and U(ν+1)&supuline;SO(ν+1)&supuline;SO(ν) for ν≥2. © 1996 American Institute of Physics.
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  • 13
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    Journal of Mathematical Physics 37 (1996), S. 2694-2730 
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    Topics: Mathematics , Physics
    Notes: A class of free quantum fields defined on the Poincaré group is described by means of their two-point vacuum expectation values. They are not equivalent to fields defined on the Minkowski space–time and they are "elementary'' in the sense that they describe particles that transform according to irreducible unitary representations of the symmetry group, given by the product of the Poincaré group and of the group SL(2,C) considered as an internal symmetry group. Some of these fields describe particles with positive mass and arbitrary spin and particles with zero mass and arbitrary helicity or with an infinite helicity spectrum. In each case the allowed SL(2,C) internal quantum numbers are specified. The properties of local commutativity and the limit in which one recovers the usual field theories in Minkowski space–time are discussed. By means of a superposition of elementary fields, one obtains an example of a field that presents a broken symmetry with respect to the group Sp(4,R) that survives in the short-distance limit. Finally, the interaction with an accelerated external source is studied and it is shown that, in some theories, the average number of particles emitted per unit of proper time diverges when the acceleration exceeds a finite critical value. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2787-2795 
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    Topics: Mathematics , Physics
    Notes: After reviewing the complete Lie group for the full Boltzmann equation, it is shown that projective transformations play a special role in the general case, and the class of invariant solutions giving rise to homoenergetic affine flows is presented. Homoenergetic affine flows in the two-dimensional case [potential U(r)∝r−2] are considered in detail: It is shown that the general solution of this problem can be essentially simplified by projective transformations. © 1996 American Institute of Physics.
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  • 15
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    Journal of Mathematical Physics 37 (1996), S. 2824-2850 
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    Notes: A discrete system of coupled waves (with nonanalytic dispersion relation) is derived in the context of the spectral transform theory for the Ablowitz–Ladik spectral problem (discrete version of the Zakharov–Shabat system). This 3-wave evolution problem is a discrete version of the stimulated Raman scattering equations, and it is shown to be solvable for arbitrary boundary value of the two radiation fields and initial value of the medium state. The spectral transform is constructed on the basis of the ∂-approach. © 1996 American Institute of Physics.
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  • 16
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    Journal of Mathematical Physics 37 (1996), S. 2872-2891 
    ISSN: 1089-7658
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    Topics: Mathematics , Physics
    Notes: We define a complete set of supertraces on the algebra SHN(ν), the algebra of observables of the N-body rational Calogero model with harmonic interaction. This result extends the previously known results for the simplest cases of N=1 and N=2 to arbitrary N. It is shown that SHN(ν) admits q(N) independent supertraces, where q(N) is a number of partitions of N into a sum of odd positive integers, so that q(N)(approximately-greater-than)1 for N≥3. Some consequences of the existence of several independent supertraces of SHN(ν) are discussed, such as the existence of ideals in associated W∞-type Lie superalgebras. © 1996 American Institute of Physics.
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  • 17
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    Journal of Mathematical Physics 37 (1996), S. 2955-2968 
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    Topics: Mathematics , Physics
    Notes: We reformulate Special Relativity by a quaternionic algebra on reals. Using real linear quaternions, we show that previous difficulties, concerning the appropriate transformations on the 3+1 space–time, may be overcome. This implies that a complexified quaternionic version of Special Relativity is a choice and not a necessity. © 1996 American Institute of Physics.
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  • 18
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    Journal of Mathematical Physics 37 (1996), S. 2815-2823 
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    Notes: The free streaming operator T is considered in a convex three dimensional region V, with diffusive multiplying boundary conditions. Some mathematical properties of T are examined by writing the particle density as an infinite series which takes into account successive reflections on ∂V, and by introducing an operator which in some sense annihilates the multiplying effect of ∂V. © 1996 American Institute of Physics.
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  • 19
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    Journal of Mathematical Physics 37 (1996), S. 2602-2627 
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    Notes: In this paper we investigate the canonical quantization of a non-Abelian topologically massive Chern–Simons theory in which the gauge fields are minimally coupled to a multiplet of scalar fields in such a way that the gauge symmetry is spontaneously broken. Such a model produces the Chern–Simons–Higgs mechanism in which the gauge excitations acquire mass both from the Chern–Simons term and from the Higgs–Kibble effect. The symmetry breaking is chosen to be only partially broken, in such a way that in the broken vacuum there remains a residual non-Abelian symmetry. We develop the canonical operator structure of this theory in the broken vacuum, with particular emphasis on the particle-content of the fields involved in the Chern–Simons–Higgs mechanism. We construct the Fock space and express the dynamical generators in terms of creation and annihilation operator modes. The canonical apparatus is used to obtain the propagators for this theory, and we use the Poincaré generators to demonstrate the effect of Lorentz boosts on the particle states. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 3022-3031 
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    Notes: A new set of polynomial states (to be called character states) are derived for Sp(4) reduced to its SU(2)×U(1) subgroup, and the relevant generator matrix elements are evaluated for generic representations (a,b) of Sp(4). [The degenerate representations (a,0) and (0,b) were treated in our previous work and are also given in this paper]. The group–subgroup in question is that of the seniority model of nuclear physics. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 3050-3061 
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    Notes: The preliminary classification of qt=f(q,qx,qxx,qxxx) is given. The results are compared with Fokas's symmetry and Mikhailov–Shabat–Sokolov formal symmetry approaches. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2682-2693 
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    Notes: In the Bayesian theory of statistical inference, as first suggested by Harold Jeffreys in highly influential work, one can employ the square root of the determinant of an n×n Fisher information matrix as a reparametrization-invariant prior (generally unnormalized) measure over an n-dimensional family (Riemannian manifold) of probability distributions. Jeffreys' ansatz is adopted here to the quantum context, that is, with regard to density matrices rather than probability distributions, by computing the quantum Fisher information matrices (associated with Helstrom and Holevo) for the three-, five-, and eight-dimensional convex sets of two-level complex, two-level quaternionic, and three-level complex systems, respectively. In both the two-level cases, the priors have been normalized to probability distributions over the 2×2 density matrices, while, in the much more computationally demanding three-level situation, no such normalization has been accomplished. An argument is made for the general form, in terms of eigenvalues, that the (unnormalized) prior should assume over the (n2−1)-dimensional convex set of n×n density matrices. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2748-2761 
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    Notes: The Manev problem (a two-body problem given by a potential of the form A/r+B/r2, where r is the distance between particles and A,B are positive constants) comprises several important physical models, having its roots in research done by Isaac Newton. We provide its analytic solution, then completely describe its global flow using McGehee coordinates and topological methods, and offer the physical interpretation of all solutions. We prove that if the energy constant is negative, the orbits are, generically, precessional ellipses, except for a zero-measure set of initial data, for which they are ellipses. For zero energy, the orbits are precessional parabolas, and for positive energy they are precessional hyperbolas. In all these cases, the set of initial data leading to collisions has positive measure. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2796-2814 
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    Notes: We discuss how to apply the dimer method to Ising models on group lattices having nontrivial topological genus g. We find that the use of group extension and the existence of both external and internal group isomorphisms greatly reduces the number of distinct Pfaffians and leads to explicit topological formulas for their sign and weight in the expansion of the partition function. The complete solution for the Ising model on the Klein lattice group L(2,7) with g=3 is given. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2851-2862 
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    Notes: In this paper, a class of degenerate (i.e., associated to a degenerate Poisson structure) completely integrable systems is studied which generalizes the so-called odd and even master systems introduced and studied by Mumford and by Vanhaecke. It is shown that all these completely integrable systems, called the generalized master systems, admit a multi-Hamiltonian formulation, and a systematic construction of this multi-Hamiltonian structure is described. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2892-2905 
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    Notes: The relationship between the two well-behaved coordinate systems of Lemaiˆtre–Tolman–Novikov, and Kruskal–Szekeres–Penrose indicates that the Schwarzschild R=0 singularity is intrinsically nonsimultaneous. It follows that the simultaneous synchronous coordinates of Wald and Yip do not exist on the complete Schwarzschild manifold. In the process, the coordinate transformations between the Schwarzschild exterior model in its various common coordinate systems and the vacuum Lemaiˆtre–Tolman model (which includes Novikov coordinates and the closed Kantowski–Sachs model) is derived. It is also shown that, contrary to statements in the literature, the closed Kantowski–Sachs model is well-behaved limit of the Lemaiˆtre–Tolman model. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2969-2978 
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    Notes: The solutions of a system of homogeneous first-order quasilinear evolution equations for which the propagation velocity depends only on the field value are characterized by their invariance under a particular type of flow. All simple wave solutions are shown to have this property. The local images of simple wave solutions are the integral curves of a system of ordinary differential equations on the field space. The model for barotropic compressible flow is an example of a system that has invariant solutions of higher rank. A solution of this system is invariant under the flow of the convective derivative if and only if it is divergence-free. The evolution of initial data is shown to be divergence-free if and only if its differential is nilpotent. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 3014-3021 
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    Notes: It is well known that knots are countable in ordinary knot theory. Recently, knots with intersections have raised a certain interest, and have been found to have physical applications. We point out that such knots—equivalence classes of loops in R3 under diffeomorphisms—are not countable; rather, they exhibit a moduli-space structure. We characterize these spaces of moduli and study their dimension. We derive a lower bound (which we conjecture being actually attained) on the dimension of the (nondegenerate components) moduli spaces, as a function of the valence of the intersection. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2376-2387 
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    Notes: The unitary irreducible representations of the central extension of the Poincaré group in 1+1 dimensions are constructed by an application of the Kirillov theory. These are then lifted to projective unitary irreducible representations of the Poincaré group. The 1+1 Galilean group is treated separately in an appendix. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2426-2456 
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    Notes: Induced invariant forms and the multiplicity labeling problem are investigated for typical summands of the tensor product of an arbitrary finite dimensional irreducible representation and a typical one, for the type I quantum superalgebras. The results are applied to obtain a general eigenvalue formula for Casimir invariants, corresponding to an arbitrary finite dimensional irreducible reference representation. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2400-2425 
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    Notes: A point group symmetrized boson representation (SBR) is introduced that is particularly convenient for describing molecular vibrations. In this paper the SBR is elucidated using the example of the molecule SF6 with Oh symmetry. The advantages of the SBR are that its basis vectors have a clear physical picture, their number is very small (equal to one-eighth of the dimension of the reducible representation for Oh), and the irreducible bases for any concrete cases can be obtained trivially from those for the general case without any projection. All the irreducible bases for the group chains Oh&supuline;D4&supuline;C4 or Oh&supuline;D4&supuline;D2 are tabulated once and for all. As an application, the Hamiltonian in the algebraic model of Iachello and Oss for stretching vibrations of the molecule SF6 is diagonalized in the symmetry adapted bases. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2472-2483 
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    Notes: The recipe of Weyl has been applied to two crystallographically distinct realizations of a regular orbit of the cyclic group of order N: the linear chain and the n-dimensional toroidal crystal, with n being the number of different prime integers dividing N, and Sylow factors of N being the Born–von Kármán periods. It follows that some fractallike symmetries of the linear chain are isomorphic images of multidimensional inversions, which are purely geometric operators. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2510-2526 
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    Notes: In this article, it is shown how to obtain objects called Eichler integrals in the mathematical literature that can be used for calculating scattering amplitudes in string theory. These Eichler integrals are also new examples of Eichler integrals with poles. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2566-2566 
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    Journal of Mathematical Physics 37 (1996), S. 1602-1616 
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    Notes: The algebra of observables of SOq(3)-symmetric quantum mechanics is extended to include the inverse 1/R of the radial coordinate and used to obtain eigenvalues and eigenfunctions of a q-deformed Coulomb Hamiltonian. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1642-1649 
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    Notes: The discrete spectrum solutions corresponding to dually charged mesoatom on the space of constant negative curvature are obtained. The discrete spectrum of energies is finite and vanishes when the magnetic charge of the nucleus exceeds the critical value. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1668-1712 
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    Notes: We present an exactly solvable quantum field theory which allows rearrangement collisions. We solve the model in the relevant sectors and demonstrate the orthonormality and completeness of the solutions, and construct the S-matrix. In light of the exact solutions constructed, we discuss various issues and assumptions in quantum scattering theory, including the isometry of the Möller wave matrix, the normalization and completeness of asymptotic states, and the nonorthogonality of basis states. We show that these common assertions are not obtained in this model. We suggest a general formalism for scattering theory which overcomes these and other shortcomings and limitations of the existing formalisms in the literature. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1772-1775 
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    Notes: It is shown that the complete symmetry group for the Kepler problem, as introduced by Krause, can be derived by Lie group analysis. The same result is true for any autonomous system. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1790-1811 
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    Notes: We consider the quantum thermal statistics à la Gibbs–Shannon–Szilard–Jaynes based on q-entropies Sq[ρ]=(q−1)−1(1−tr(ρq)) (0〈q≠1) and the non-standard "internal energy'' functionals Uq[ρ]=tr(ρqH) proposed by C. Tsallis [J. Stat. Phys. 52, 479–487 (1988)]. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1106-1114 
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    Notes: It is shown that for the Calogero–Cohn-type upper bounds on the number of bound states of a negative spherically symmetric potential V(r), in each angular momentum state, that is, bounds containing only the integral ∫∞0||V(r)||1/2 dr, the condition V′(r)≥0 is not necessary, and can be replaced by the less stringent condition (d/dr)[r1−2p(−V)1−p]≤0, 1/2≤p〈1, which allows oscillations in the potential. The constants in the bounds are accordingly modified, depend on p and l, and tend to the standard value for p=1/2. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1115-1127 
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    Notes: Fractional supersymmetry denotes a generalization of supersymmetry which may be constructed using a single real generalized Grassmann variable, θ=θ¯,θn=0, for arbitrary integer n=2,3,.... An explicit formula is given in the case of general n for the transformations that leave the theory invariant, and it is shown that these transformations possess interesting group properties. It is shown also that the two generalized derivatives that enter the theory have a geometric interpretation as generators of left and right transformations of the fractional supersymmetry group. Careful attention is paid to some technically important issues, including differentiation, that arise as a result of the peculiar nature of quantities such as θ. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1197-1203 
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    Notes: The concept of geometric phase for a closed circuit in the ray space is applied to the manifold of generalized coherent states defined as the eigenstates of isotopic spin charges. The geometry of the state manifold is elucidated through a calculation of the Gaussian curvature. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1171-1181 
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    Notes: Nonstationary Schrödinger equation with a periodic finite band potential p(x) is considered. The Green's function G(x,x′,t) of this equation is investigated when t→∞. Asymptotics for G(x,x′,t) are specified. It is shown that for large "velocities'' v=(x−x′)/t the principal term in asymptotics of G(x,x′,t), t→∞ coincides with the Green's function for p=0. The principal term in the asymptotics of G(x,x′,t) in the case v→∞ is equal to a sum of Green's functions of unperturbed problems for particles whose masses are equal to effective masses of the Hill operator under investigation. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1244-1252 
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    Notes: Mechanics is developed over a differentiable manifold as space of possible positions. Time is considered to fill a one-dimensional Riemannian manifold, so having the metric as lapse. Then the system is quantized with covariant instead of partial derivatives in the Schrödinger operator. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1234-1243 
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    Notes: The both lower and upper estimates of the lower bound λ20 of the essential spectrum σess(H2) of the square of the Dirac Hamiltonian H for a spin 1/2 neutral particle with an anomalous magnetic moment in an asymptotically constant magnetic field are obtained. It is found that in a restricted case, λ20≤m2, where m is the mass of the particle. Moreover, it is proven that σess(H2)=[λ20,∞). In particular, in the case where the space dimension d is odd and d≥3, σess(H)=(−∞,−λ0]∪[λ0,∞). In the case where d=2 and 3, σess(H) is exactly identified. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1268-1286 
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    Notes: The modular structure of the free Bose gas in the critical regime of couplings is completely described by certain Gaussian Markovian (on a circle) nonergodic thermal process. Gentle perturbations of the arising Gaussian stochastic structure are controlled rigorously and the arising non-quasi-free W* KMS structure is shown to be nonergodic in certain range of couplings. The preserved nonergodicity seems to be connected to the presence of the Bose–Einstein condensate in the constructed models of interacting bosons. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1336-1348 
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    Notes: In this article a nonlinear one-dimensional stationary transport equation with general boundary conditions is considered where an abstract boundary operator relates the incoming and the outgoing fluxes. Existence results are proved in the case where the collision operator is of the Hammerstein type. In particular, it is shown that these results remain valid for multidimensional geometry with vacuum boundary conditions. Sufficient conditions are given in terms of collision frequency and scattering kernel assuring the existence and uniqueness of solutions. The article ends with the discussion of the case of multiplying boundary conditions. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1414-1433 
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    Notes: We prove that static, spherically symmetric, asymptotically flat soliton and black hole solutions of the Einstein–Yang–Mills equations are unstable for arbitrary gauge groups, at least for the "generic'' case. This conclusion is derived without explicit knowledge of the possible equilibrium solutions. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1434-1448 
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    Notes: Up to a conjecture in Riemannian geometry, we significantly strengthen a recent theorem of Eardley by proving that a compact region in an initial data surface that is collapsing sufficiently fast in comparison to its surface-to-volume ratio must contain a future trapped region. In addition to establishing this stronger result, the geometrical argument used does not require any asymptotic or energy conditions on the initial data. It follows that if such a region can be found in an asymptotically flat Cauchy surface of a spacetime satisfying the null-convergence condition, the spacetime must contain a black hole with the future trapped region therein. Further, up to another conjecture, we prove a strengthened version of our theorem by arguing that if a certain function (defined on the collection of compact subsets of the initial data surface that are themselves three-dimensional manifolds with boundary) is not strictly positive, then the initial data surface must contain a future trapped region. As a byproduct of this work, we offer a slightly generalized notion of a future trapped region as well as a new proof that future trapped regions lie within the black hole region. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 2053-2070 
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    Notes: We find a one-parameter family of quadratic Poisson structures on R4×SL(2,C) which satisfies the properties: (a) that it reduces to the standard Poincaré algebra for a particular limiting value of the parameter (which we associate with the "canonical limit''), as well as, (b) that it is preserved under the Lie–Poisson action of the Lorentz group (and the Lie–Poisson transformations reduce to canonical ones in the canonical limit). As with the Poincaré algebra, our deformed Poincaré algebra has two Casimir functions which correspond to "mass'' and "spin.'' The constant mass and spin surfaces in R4×SL(2,C) define symplectic leaves which we parametrize with space–time coordinates, momenta, and spin. We thereby obtain realizations of the deformed Poincaré algebra for both spinning and spinless particles. The formalism can be applied for finding a one-parameter family of canonically inequivalent descriptions of the photon. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1091-1099 
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    Notes: We analyze the initial value problem for spinor fields obeying the Dirac equation, with particular attention to the characteristic surfaces. The standard Cauchy initial value problem for first-order differential equations is to construct a solution function in a neighborhood of space and time from the values of the function on a selected initial value surface. On the characteristic surfaces the solution function may be discontinuous, so the standard Cauchy construction breaks down. For the Dirac equation the characteristic surfaces are null surfaces. An alternative version of the initial value problem may be formulated using null surfaces; the initial value data needed differs from that of the standard Cauchy problem. We study, in particular, the intersecting pair of characteristics t=x and t=−x (and supress the y and z dependence). In this case the values of separate components of the spinor function on the intersecting pair of null surfaces comprise the necessary initial value data. We present an expression for the construction of a solution from the null surface data; two analogs of the quantum mechanical Hamiltonian operator determine the evolution of the system. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1128-1147 
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    Notes: The O(N) nonlinear sigma model in a D-dimensional space of the form RD−M×TM, RD−M×SM, or TM×SP is studied, where RM, TM, and SM correspond to flat space, a torus, and a sphere, respectively. Using zeta-regularization and the 1/N expansion, the corresponding partition functions—for deriving the free energy—and the gap equations are obtained. In particular, the free energy at the critical point on R2q+1×S2p+2 vanishes in accordance with the conformal equivalence to the flat space RD. Numerical solutions of the gap equations at the critical coupling constants are given for several values of D. The properties of the partition function and its asymptotic behavior for large D are discussed. In a similar way, a higher-derivative nonlinear sigma model is investigated, too. The physical relevance of our results is discussed. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1161-1170 
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    Notes: Previous path integral treatments of Yang–Mills on a Riemann surface automatically sum over principal fiber bundles of all possible topological types in computing quantum expectations. This paper extends the path integral formulation to treat separately each topological sector. The formulation is sufficiently explicit to calculate Wilson line expectations exactly. Further, it suggests two new measures on the moduli space of flat connections, one of which proves to agree with the small-volume limit of the Yang–Mills measure. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1182-1196 
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    Notes: The eigenvalue moment method (EMM) has proven to be an effective technique for generating converging lower and upper bounds to the bosonic ground state energy of singular, strongly coupled, quantum systems. Application of EMM theory requires an appropriate linearization of the highly nonlinear Hankel–Hadamard (HH) moment determinant constraints for the (n+1)×(n+1) Hankel matrices Mn[u]≡Mˆn0+∑i=1msMˆniu i), dependent on the missing moment variables {u(i)}≡u. We propose an alternate variational formulation utilizing the functions Det(Mn+1[u])/Det(Mn[u]), which we prove to be locally convex over the missing moment subset satisfying the HH positivity conditions Det(Mν[u])(approximately-greater-than)0, for ν≤n. Additional features of this variational formulation facilitate its application to important problems such as the octic, sextic, and quartic anharmonic oscillators. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1259-1267 
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    Notes: Construction of the stress tensor for a low differential order field theory on translation-invariant space is routine. If the underlying space is rotation, or Lorentz, invariant, an equivalent symmetric tensor can be found as well. Extension to nonlocal field equations, common, for example, in the statistical mechanical theory of fluids, is not routine and is carried out in this paper. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1218-1233 
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    Notes: The line bundles that arise in the holonomy interpretations of the geometric phase display curious similarities to those encountered in the statement of the Borel–Weil–Bott theorem of the representation theory. The remarkable relationship between the mathematical structure of the geometric phase and the classification theorem for complex line bundles provides the necessary tools for establishing the relevance of the Borel–Weil–Bott theorem to Berry's adiabatic phase. This enables one to define a set of topological charges for arbitrary compact connected semisimple dynamical Lie groups. These charges signify the topological content of the phase. They can be explicitly computed. In this paper, the problem of the determination of the parameter space of the Hamiltonian is also addressed. It is shown that, in general, the parameter space is either a flag manifold or one of its submanifolds. A simple topological argument is presented to indicate the relation between the Riemannian structure on the parameter space and Berry's connection. The results about the fiber bundles and group theory are used to introduce a procedure to reduce the problem of the nonadiabatic (geometric) phase to Berry's adiabatic phase for cranked Hamiltonians. Finally, the possible relevance of the topological charges of the geometric phase to those of the non-Abelian monopoles is pointed out. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1287-1313 
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    Notes: A comprehensive statistical mechanics treatment of (non)interacting deformable planar droplets of arbitrary rigidity is developed. Closed form exact analytic results are obtained for the area statistics of a single droplet and for the decay rates of metastable states characteristic of the first-order phase transitions for an assembly of such droplets. To select the correct form of the interaction between the droplets, the reparametrization invariance is taken into account. Most of the known two-dimensional lattice models are obtained as the limiting cases of the interacting droplet model discussed in the text. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1382-1392 
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    Notes: In this paper we give a simple formula to obtain hereditary symmetries related to the isospectral eigenvalue problem of integrable equations. Using this formula, (i) we prove that eigenfunctions of hereditary strong symmetry are symmetries for the whole hierarchy, which improves the result of Fokas and Anderson [J. Math. Phys. 23, 1066 (1982)]; (ii) we find new integrable equations; and (iii) we give strong symmetries of these new integrable equations and various equations for eigenfunctions of the isospectral eigenvalue problems. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1356-1381 
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    Notes: We present the results of further analysis of the integrability properties of the N=4 supersymmetric Korteweg–de Vries (KdV) equation deduced earlier by two of us [F. Delduc and E. Ivanov, Phys. Lett. B 309, 312 (1993)] as a Hamiltonian flow on N=4 SU(2) superconformal algebra in the harmonic N=4 superspace. To make this equation and the relevant Hamiltonian structures more tractable, we reformulate it in the ordinary N=4 and further in N=2 superspaces. In N=2 superspace it is represented by a coupled system of evolution equations for a general N=2 superfield and two chiral and antichiral superfields, and involves two independent real parameters, a and b. We construct a few first bosonic conserved charges in involution, of dimensions from 1 to 6, and show that they exist only for the following choices of the parameters: (i) a=4, b=0; (ii) a=−2, b=−6; (iii) a=−2, b=6. The same values are needed for the relevant evolution equations, including N=4 KdV itself, to be bi-Hamiltonian. We demonstrate that the above three options are related via SU(2) transformations and actually amount to the SU(2) covariant integrability condition found in the harmonic superspace approach. Our results provide a strong evidence that the unique N=4 SU(2) super KdV hierarchy exists. Upon reduction to N=2 KdV, the above three possibilities cease to be equivalent. They give rise to the a=4 and a=−2 N=2 KdV hierarchies, which thus prove to be different truncations of the single N=4 SU(2) KdV one. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1449-1460 
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    Notes: Radiation-filled Friedmann–Robertson–Walker universes are quantized according to the Arnowitt–Deser–Misner formalism in the conformal-time gauge. Unlike previous treatments of this problem, here both closed and open models are studied, only square-integrable wave functions are allowed, and the boundary conditions to ensure self-adjointness of the Hamiltonian operator are consistent with the space of admissible wave functions. It turns out that the tunneling boundary condition on the universal wave function is in conflict with self-adjointness of the Hamiltonian. The evolution of wave packets obeying different boundary conditions is studied, and it is generally proven that all models are nonsingular. Given an initial condition on the probability density under which the classical regime prevails, it is found that a closed universe is certain to have an infinite radius, a density parameter Ω=1 becoming a prediction of the theory. Quantum stationary geometries are shown to exist for the closed universe model, but oscillating coherent states are forbidden by the boundary conditions that enforce self-adjointness of the Hamiltonian operator. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1059-1075 
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    Notes: It is well known that there are fourteen independent algebraic invariants of the four-dimensional Riemann tensor. Several authors have written down a set of fourteen independent invariants, but it is still not known how other invariants can be expressed in terms of these sets. This paper investigates this problem by looking for relationships between invariants of the Riemann tensor. Essentially the problem turns out to be analogous to finding relationships between the invariants of two 3×3 matrices, one of which is symmetric and trace-free and the other Hermitian. A number of identities between the invariants can be obtained simply by using a generalization of the Cayley–Hamilton theorem but others, which depend on the symmetry of the matrices, are considerably more complex. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 1086-1088 
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    Notes: We present a counter example to a theorem given by Amir et al. [J. Math. Phys. 35, 3005–3012 (1994)]. We also comment on a misleading statement of the same reference. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 535-553 
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    Notes: We examine the problem of the evaluation of both the propagator and of the partition function of a spinning particle in an external field at the classical as well as the quantum level, in connection with the asserted exactness of the stationary phase approximation. At the classical level we argue that exactness of this approximation stems from the fact that the dynamics (on the two-sphere S2) of a spinning particle in a magnetic field is the reduction from R4 to S2 of a linear dynamical system on R4. At the quantum level, however, and within the path integral approach, the restriction, inherent to the use of the stationary phase approximation, to regular paths clashes with the fact that no regulators are present in the action that enters the path integral. This is shown to lead to a prefactor for the path integral that is strictly divergent, except in the classical limit. A critical comparison is made with the various approaches that have been presented in the literature. The validity of a formula given in literature for the spin propagator is extended to the case of motion in an arbitrary magnetic field. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 702-718 
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    Notes: The (2,0) supersymmetric Wess–Zumino–Polyakov action is constructed and the (2,0) superconformal anomaly is given. The anomalous Ward-identity in the right sector is derived and the known operator product expansion of the N=2 superstress energy tensor is recovered. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 719-731 
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    Notes: In this paper, by using the multiscale operator and based on the Beylkin's formula [J. Math. Phys. 26, 99–108 (1985)], the inversion method of velocity singularities is presented, and by applying the multiscale operator to upward scattered data represented by the Kirchhoff approximation, the multiscale imaging formula is shown. For the band-limited inverse problem, based on the multiscale imaging formula in this paper, the behavior of the velocity singularities can be analyzed across the multiscale and the formula to reconstruct the velocity is obtained from the output of the multiscale operator interpreted in the terms of the Kirchhoff-approximate data. Particularly, at wide offset and even postcritical case, for the full-band input data, the same result with Beylkin's in the above reference about the velocity discontinuities is obtained. Our method in this paper can suppress the effects of the noise in the real world data and analyze the effect produced by band-limited input data. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 953-964 
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    Notes: We describe a q-deformation of the Lorentz group in terms of a q-deformation of the van der Waerden spinor algebra. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 933-941 
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    Notes: Analytic continuation plays a key role in many problems in physics. A central problem is the implementation of a stabilized continuation from approximate numerical data specified on an interior segment γ within the holomorphy domain. The solution to that problem presented in this paper is expressed in terms of a Fredholm integral equation of the second kind which refers only to the physical region γ ; in this latter respect it differs from other approaches to the same problem which are normally formulated on the boundary, and has the considerable advantage of dealing directly with the physically relevant functions. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 987-1003 
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    Notes: A new general eigenvalue formula for the eigenvalues of Casimir invariants, for the type-I quantum superalgebras, is applied to the construction of link polynomials associated with any finite dimensional unitary irrep for these algebras. This affords a systematic construction of new two-variable link polynomials associated with any finite dimensional irrep (with a real highest weight) for the type-I quantum superalgebras. In particular infinite families of nonequivalent two-variable link polynomials are determined in fully explicit form. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6012-6017 
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    Notes: A third order Monge-Ampère type equation of associativity that Dubrovin has obtained in 2-d topological field theory is formulated in terms of a variational principle subject to second class constraints. Using Dirac's theory of constraints this degenerate Lagrangian system is cast into Hamiltonian form and the Hamiltonian operator is obtained from the Dirac bracket. There is a new type of Kac-Moody algebra that corresponds to this Hamiltonian operator. In particular, it is not a W-algebra. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6074-6085 
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    Notes: We discuss the N=2 SU(2) Yang–Mills theory coupled with a massive matter in the weak coupling. In particular, we obtain the instanton expansion of its prepotential. Instanton contributions in the mass-less limit are completely reproduced. We study also the double scaling limit of this massive theory and find that the prepotential with instanton corrections in the double scaling limit coincides with that of N=2 SU(2) Yang–Mills theory without matter. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6121-6129 
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    Notes: Based on the idea of quantum groups and para-Grassmannian variables, we present a generalization of supersymmetric classical mechanics with a deformation parameter q=exp(2πi/k) dealing with the k=3 case. The coordinates of the q-superspace are a commuting parameter t and a para-Grassmannian variable θ, where θ3=0. The generator and covariant derivative are obtained, as well as the action for some possible superfields. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6302-6310 
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    Notes: In the teleparallel equivalent of general relativity the energy density of asymptotically flat gravitational fields can be naturally defined as a scalar density restricted to a three-dimensional spacelike hypersurface Σ. Integration over the whole Σ yields the standard ADM energy. Here we obtain the formal expression of the localized energy for a Kerr black hole. The expression of the energy inside a surface of constant radius can be explicitly calculated in the limit of small a, the specific angular momentum. Such expression turns out to be exactly the same as the one obtained by means of the method proposed recently by Brown and York [Phys. Rev. D 47, 1407 (1993)]. We also calculate the energy contained within the outer horizon of the black hole, for any value of a. The result is practically indistinguishable from E=2Mir, where Mir is the irreducible mass of the black hole. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6367-6374 
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    Notes: We construct a C-algebra C associated with an R-matrix of the 2-state chiral Potts model. This algebra will be shown to coincide with the Sklyanin algebra at an 8-torsion point and, in the self-dual case, with Uq(sl2) at the fourth root of unity. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6414-6438 
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    Notes: In this paper we characterize the possible symmetry groups of wave equations and certain evolutionary generalizations, in a single time variable and one or more spatial variables. Furthermore, we describe a complete classification of two-dimensional wave equations utt=F[u] and potential evolutionary equations uxt=F[u] having a point or contact symmetry group. The results rely on Lie's classification of planar transformation groups and their relative differential invariants. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6530-6569 
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    Notes: We develop a simple computational tool for SU(3) analogous to Bargmann's calculus for SU(2). Crucial new inputs are (i) explicit representation of the Gelfand–Zetlin basis in terms of polynomials in four variables and positive or negative integral powers of a fifth variable, (ii) an auxiliary Gaussian measure with respect to which the Gelfand–Zetlin states are orthogonal but not normalized, (iii) simple generating functions for generating all basis states and also all invariants. As an illustration of our techniques, an algebraic formula for the Clebsch–Gordan coefficients is obtained for the first time. This involves only Gaussian integrations. Thus SU(3) is made as accessible for computations as SU(2) is. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6582-6585 
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    Notes: A version of Schur's lemma is proven that elucidates some issues raised by that paper. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6590-6590 
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    Journal of Mathematical Physics 37 (1996), S. 6311-6323 
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    Notes: Based on a closed formula for a star product of Wick type on CPn, which has been discovered in an earlier article of the authors, we explicitly construct a subalgebra of the formal star algebra (with coefficients contained in the uniformly dense subspace of representative functions with respect to the canonical action of the unitary group) that consists of converging power series in the formal parameter, thereby giving an elementary algebraic proof of a convergence result already obtained by Cahen, Gutt, and Rawnsley. In this subalgebra the formal parameter can be substituted by a real number α: the resulting associative algebras are infinite dimensional, except for the case α=1/K, K a positive integer, where they turn out to be isomorphic to the finite-dimensional algebra of linear operators in the Kth energy eigen- space of an isotropic harmonic oscillator with n+1 degrees of freedom. Other examples like the 2n torus and the Poincaré disk are discussed. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6324-6348 
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    Notes: We study relations between the deformed cotangent bundle (T*B)q for the Borel subgroup B of a given simple Lie group G, the quantum Lie algebra Jq associated with the corresponding quantum group Gq and the matrices generating Clebsch–Gordan coefficients for Jq. We reveal the connection of these objects to quantum analog of the model space M and q-tensor operators. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5458-5475 
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    Notes: We show that a rigorous statistical mechanics description of some Dirichlet series is possible. Using the abstract polymer model language of statistical mechanics and the polymer expansion theory we characterize the low activity phase by the suitable exponential decay of the truncated correlation functions. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5455-5457 
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    Notes: In a recent paper Mason and Kgathi have integrated some well-known thermodynamic identities for an equation of state p=nkT and thereby have obtained some explicit expressions for the thermodynamic variables concerned. In the present paper we integrate the same identities for a more general equation of state p=p(n,T) and thereby obtain more general expressions for the same thermodynamic variables. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5551-5576 
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    Notes: Differential–difference equations of the form ün=Fn(t,un−1,un,un+1) are classified according to their continuous Lie point symmetry groups. It is shown that for nonlinear equations, the symmetry group can be at most seven-dimensional. The integrable Toda lattice is a member of this class and has a four-dimensional symmetry group. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 6586-6589 
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    Notes: We discuss the differing definitions of complex and quaternionic projective group representations employed by us and by Emch. The definition of Emch (termed here a strong projective representation) is too restrictive to accommodate quaternionic Hilbert space embeddings of complex projective representations. Our definition (termed here a weak projective representation) encompasses such embeddings, and leads to a detailed theory of quaternionic, as well as complex, projective group representations. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5273-5296 
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    Notes: One may introduce at least three different Lie algebras in any Lagrangian field theory: (i) the Lie algebra of local BRST cohomology classes equipped with the odd Batalin–Vilkovisky antibracket, which has attracted considerable interest recently; (ii) the Lie algebra of local conserved currents equipped with the Dickey bracket; and (iii) the Lie algebra of conserved, integrated charges equipped with the Poisson bracket. We show in this paper that the subalgebra of (i) in ghost number −1 and the other two algebras are isomorphic for a field theory without gauge invariance. We also prove that, in the presence of a gauge freedom, (ii) is still isomorphic to the subalgebra of (i) in ghost number −1, while (iii) is isomorphic to the quotient of (ii) by the ideal of currents without charge. In ghost number different from −1, a more detailed analysis of the local BRST cohomology classes in the Hamiltonian formalism allows one to prove an isomorphism theorem between the antibracket and the extended Poisson bracket of Batalin, Fradkin, and Vilkovisky. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5342-5350 
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    Notes: We study the topological Yang–Mills–Higgs theories in two and three dimensions and the topological Yang–Mills theory in four dimensions in a unified framework of superconnections. In this framework, we first show that a classical action of topological Yang–Mills type can provide all three classical actions of these theories via appropriate projections. Then we obtain the Becchi–Rouet–Stora–Tyutin (BRST) and anti-BRST transformation rules encompassing these three topological theories from an extended definition of curvature and a geometrical requirement of the Bianchi identity. This is an extension of Perry and Teo's work in the topological Yang–Mills case. Finally, comparing this result with our previous treatment in which we used the "modified horizontality condition,'' we provide a meaning of the Bianchi identity from the BRST symmetry viewpoint and thus interpret the BRST symmetry in a geometrical setting. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5412-5423 
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    Notes: A one-dimensional boson–fermion model with two-body interactions between the two types of chiral fermions is considered. It is shown that the model is exactly soluble and the general Bethe eigenstates are constructed. On the basis of the Bethe ansatz equations, the ground state, the low lying elementary excitations, and the thermodynamics are also given in some closed integral equations. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5444-5454 
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    Notes: The aim of this paper is to develop the classical lattice models with unbounded spin to the case of nonquadratic polynomial interaction. We demonstrate that the distinct relation between the growths of potentials leads to the uniqueness and the fast decay of correlations for Gibbs measure. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5496-5508 
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    Notes: One-dimensional time-dependent potentials are considered for which an invariant can be expressed in terms of the potential and the momentum according to the formulation of Giacomini. New solutions of Giacomini's equations are derived. In addition, possibilities are discussed for extending Giacomini's approach to more general systems. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5087-5110 
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    Notes: We present a semiclassical theory of weak disorder effects in small structures and apply it to the magnetic response of non-interacting electrons confined in integrable geometries. We discuss the various averaging procedures describing different experimental situations in terms of one- and two-particle Green functions. We demonstrate that the anomalously large zero-field susceptibility characteristic of clean integrable structures is only weakly suppressed by disorder. This damping depends on the ratio of the typical size of the structure with the two characteristic length scales describing the disorder (elastic mean-free-path and correlation length of the potential) in a power-law form for the experimentally relevant parameter region. We establish the comparison with the available experimental data and we extend the study of the interplay between disorder and integrability to finite magnetic fields. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5259-5268 
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    Journal of Mathematical Physics 37 (1996), S. 1-5 
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    Notes: Usually quantum chains with quantum group symmetry are associated with representations of quantized universal algebras Uq(g). Here we propose a method for constructing quantum chains with Cq(G) global symmetry, where Cq(G) is the algebra of functions on the quantum group. In particular we will construct a quantum chain with GLq(2) symmetry which interpolates between two classical Ising chains. It is shown that the Hamiltonian of this chain satisfies the generalized braid group algebra. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5195-5206 
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    Notes: Asymptotic estimates which relate the diffusion of wave packets on discrete lattices to Hausdorff dimensions of the local density of states are discussed. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 5158-5170 
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    Notes: I present here some results on the mean field theory approach to the statistical mechanics of a D-dimensional array of Josephson junctions in the presence of a magnetic field. The mean field theory equations are obtained by computing the thermodynamical properties. In the high temperature region in the limit D→∞, where the problem is simplified, this limit defines the mean field approximation. Close to the transition point the system behaves very similar to a particular form of spin glasses, i.e., to gauge glasses. We have noticed that in this limit the evaluation of the coefficients of the high temperature expansion may be mapped onto the computation of some matrix elements for the q-deformed harmonic oscillator. The same arguments can be used to predict the thermodynamical properties in the mean field limit. These results can be extended to the low temperature phase using a conjecture on the equivalence of some system without disorder with appropriate random systems. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 430-437 
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    Notes: We analyze a relativistic model for superdense stars proposed by Tikekar [R. Tikekar, J. Math. Phys. 31, 2454 (1990)]. In this model the hypersurfaces generated by {t=const} have the geometry of the 3-spheroid which gives the solutions a clear geometrical characterization. The solution of the Einstein field equations is reduced to integrating a second order ordinary differential equation. New classes of solutions are presented by restricting the choice of the spheroidal parameter K so that polynomial solutions are admitted for the first solution and then we find that there exists another solution which is a product of polynomials and algebraic functions. A remarkable feature of the class of solutions generated is that they are expressible completely in terms of polynomials and algebraic functions. Some physical aspects of the solutions are briefly considered. We regain the Tikekar solution as a special case when K=−7. As another example we explicitly present the form of the solution when K=−2. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 474-483 
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    Notes: We introduce Z3-graded objects which are the generalization of the more familiar Z2-graded objects that are used in supersymmetric theories and in many models of non-commutative geometry. First, we introduce the Z3-graded Grassmann algebra, and we use this object to construct the Z3-matrices, which are the generalizations of the supermatrices. Then, we generalize the concepts of supertrace and superdeterminant. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 508-523 
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    Notes: It is our purpose here to show that the spinor theory admits generalization for curved spaces with local anisotropy (for example, for Finsler, Lagrange, and generalized Lagrange spaces). © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 4480-4483 
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    Notes: In this work the concept of entropy of a dynamical system, as given by Kolmogorov, is generalized in the sense of Tsallis. It is shown that this entropy is an isomorphism invariant, being complete for Bernoulli schemes. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 4484-4513 
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    Notes: The nonunitary r-matrix theory and the associated bi- and triHamiltonian schemes are considered. The language of Poisson pencils and of their formal Casimirs is applied in this framework to characterize the biHamiltonian chains of integrals of motion, pointing out the role of the Schur polynomials in these constructions. This formalism is subsequently applied to the periodic Toda lattice. Some different algebraic settings and Lax formulations proposed in the literature for this system are analyzed in detail, and their full equivalence is exploited. In particular, the equivalence between the loop algebra approach and the method of differential-difference operators is illustrated; moreover, two alternative Lax formulations are considered, and appropriate reduction algorithms are found in both cases, allowing us to derive the multiHamiltonian formalism from r-matrix theory. The systems of integrals for the periodic Toda lattice known after Flaschka and Hénon, and their functional relations, are recovered through systematic application of the previously outlined schemes. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 4549-4556 
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    Notes: Two toy models are considered within the framework of noncommutative differential geometry. In the first one, the Einstein action of the Levi–Civita connection is computed for the algebra of matrix valued functions on a torus. It is shown that, assuming some constraints on the metric, this action splits into a classical-like, a quantum-like and a mixed term. In the second model, an analogue of the Palatini method of variation is applied to obtain critical points of the Einstein action functional for M4(R). It is pointed out that a solution to the Palatini variational problem is not necessarily a Levi–Civita connection. In this model, no additional assumptions regarding metrics are made. © 1996 American Institute of Physics.
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    Journal of Mathematical Physics 37 (1996), S. 4584-4589 
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    Notes: It is shown that if (gμν,Fμν) is an exact solution of the Einstein–Maxwell equations and lμ is a principal null direction of Fμν then (gμν+2Hlμlν,Fμν) is also an exact solution of the Einstein–Maxwell equations if and only if (2Hlμlν,0) satisfies the Einstein–Maxwell equations linearized about (gμν,Fμν). It is also shown that an analogous result applies in the case of the Einstein–Weyl equations if lμ is parallel to the flux vector of the neutrino field. © 1996 American Institute of Physics.
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