Renormalization and Dimensional Regularization for a Scalar Field with Gauss–Bonnet-Type Coupling to Curvature

We consider a scalar field with a Gauss–Bonnet-type coupling to the curvature in a curved space–time. For such a quadratic coupling to the curvature, the metric energy–momentum tensor does not contain derivatives of the metric of orders greater than two. We obtain the metric energy–momentum tensor and find the geometric structure of the first three counterterms to the vacuum averages of the energy–momentum tensors for an arbitrary background metric of an N-dimensional space–time. In a homogeneous isotropic space, we obtain the first three counterterms of the n-wave procedure, which allow calculating the renormalized values of the vacuum averages of the energy–momentum tensors in the dimensions N=4,5. Using dimensional regularization, we establish that the geometric structures of the counterterms in the n-wave procedure coincide with those in the effective action method.     

The n-Wave Procedure and Dimensional Regularization for the Scalar Field in a Homogeneous Isotropic Space

We obtain expressions for the vacuum expectations of the energy–momentum tensor of the scalar field with an arbitrary coupling to the curvature in an N-dimensional homogeneous isotropic space for the vacuum determined by diagonalization of the Hamiltonian. We generalize the n-wave procedure to N-dimensional homogeneous isotropic space–time. Using the dimensional regularization, we investigate the geometric structure of the terms subtracted from the vacuum energy–momentum tensor in accordance with the n-wave procedure. We show that the geometric structures of the first three subtractions in the n-wave procedure and in the effective action method coincide. We show that all the subtractions in the n-wave procedure in a four- and five-dimensional homogeneous isotropic space correspond to a renormalization of the coupling constants of the bare gravitational Lagrangian.     

Dimensional Regularization and the n-Wave Procedure for Scalar Fields in Many-Dimensional Quasi-Euclidean Spaces

We obtain the vacuum expectation values of the energy–momentum tensor for a scalar field arbitrarily coupled to a curvature in the case of an N-dimensional quasi-Euclidean space–time; the vacuum is defined in accordance with the Hamiltonian diagonalization method. We extend the n-wave procedure to the many-dimensional case. We find all the counterterms in the case N=5 and the counterterms for the conformal scalar field in the cases N=6,7. We determine the geometric structure of the first three counterterms in the N-dimensional case. We show that all the subtractions in the four-dimensional case and the first three subtractions in the many-dimensional case correspond to the renormalization of the parameters in the bare gravitational Lagrangian. We discuss the geometric structure of the other counterterms in the many-dimensional case and the problem of eliminating the conformal anomaly in the four-dimensional case.     

Quantum dissipative systems. II. String in a curved affine—Metric spacetime

A closed bosonic string in a curved affine—metric spacetime is considered as an example of dissipative quantum field theory. The conformal anomaly of the trace of the energy—momentum tensor for the string on the affine—metric manifold is investigated. The two-loop metric beta function for the two-dimensional nonlinear dissipative sigma model is calculated. Examples of nonflat manifolds that lead to ultraviolet-finite sigma models are found.Institute of Nuclear Physics, Moscow State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 101, No. 1, pp. 38–46, October, 1994.     

The energy—Momentum tensor as the source of the gravitational field and the effective Riemannian spacetime

It is shown in this paper that the assumption of the matter energy—momentum tensor is the source of the gravitational field leads naturally to an effective Riemannian geometry of spacetime.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 104, No. 3, pp. 538–542, September, 1995.     

Decomposition of polynomial matrices into factors with prescribed canonical diagonal forms

We give a test for decomposability of a polynomial matrix over an arbitrary infinite field into factors with prescribed canonical diagonal forms whose product is the canonical diagonal form of the given matrix. We exhibit a method of actually constructing such decompositions of polynomial matrices.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 32, 1990, pp. 17–19.     

Absence of Embedded Mass Shells: Cerenkov Radiation and Quantum Friction

We show that, in a model where a non-relativistic particle is coupled to a quantized relativistic scalar Bose field, the embedded mass shell of the particle dissolves in the continuum when the interaction is turned on, provided the coupling constant is sufficiently small. More precisely, under the assumption that the fiber eigenvectors corresponding to the putative mass shell are differentiable as functions of the total momentum of the system, we show that a mass shell could exist only at a strictly positive distance from the unperturbed embedded mass shell near the boundary of the energy–momentum spectrum.     

General-covariant quantum mechanics in Riemannian space-time III. The Dirac particle

A general covariant analog of standard nonrelativistic quantum mechanics with relativistic corrections is constructed for the Dirac particle in a normal geodesic frame in general Riemannian space-time. Not only the Pauli equation with a Hermitian Hamiltonian and the pre-Hilbert structure of the space of its solutions, but also matrix elements of the Hermitian operators of momentum, (curvilinear) spatial coordinates, and spin of the particle, are deduced, as a general-covariant asymptotic approximation in c^–2 (c is the velocity of light), to their naturally determined general-relativistic pre-images. It is shown that the Pauli equation Hamiltonian, generated by the Dirac equation, is unitary-equivalent to the energy operator generated by the metric energymomentum tensor of the spinor field. Commutation and other properties of the observables associated with variation in the geometrical background of quantum mechanics are briefly discussed.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 106, No. 1, pp. 122–132, January, 1996.     

The classical analog of intertwining operators in the relativistic Hamiltonian mechanics of a system of particles

In the context of nonquantum Hamiltonian formalism of the relativistic theory of direct interaction we construct a canonical transformation of the collective variables of center of mass type which transforms the canonical generators of the Poincaré algebra in one form of dynamics into the corresponding generators in another form of dynamics.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 32, 1990, pp. 62–65.     

On the variation of a metric and its application

Some of the variation formulas of a metric were derived in the literatures by using the local coordinates system, In this paper, We give the first and the second variation formulas of the Riemannian curvature tensor, Ricci curvature tensor and scalar curvature of a metric by using the moving frame method. We establish a relation between the variation of the volume of a metric and that of a submanifold. We find that the latter is a consequence of the former. Finally we give an application of these formulas to the variations of heat invariants. We prove that a conformally flat metric g is a critical point of the third heat invariant functional for a compact 4-dimensional manifold M, then （M, g） is either scalar flat or a space form.     

On the microcanonical solution of a system of fully coupled particles

We study the Hamiltonian mean field (HMF) model, a system of N fully coupled particles, in the microcanonical ensemble. We use the previously obtained free energy in the canonical ensemble to derive entropy as a function of energy, using Legendre transform techniques. The temperature–energy relation is found to coincide with the one obtained in the canonical ensemble and includes a metastable branch which represents spatially homogeneous states below the critical energy. “Water bag” states, with removed tails momentum distribution, lying on this branch, are shown to relax to equilibrium on a time which diverges linearly with N in an energy region just below the phase transition.     

Approximate bound state solutions of Dirac equation with Hulthén potential including Coulomb-like tensor potential

We solve the Dirac equation approximately for the attractive scalar S(r) and repulsive vector V(r) Hulthén potentials including a Coulomb-like tensor potential with arbitrary spin-orbit coupling quantum number κ. In the framework of the spin and pseudospin symmetric concept, we obtain the analytic energy spectrum and the corresponding two-component upper- and lower-spinors of the two Dirac particles by means of the Nikiforov-Uvarov method in closed form. The limit of zero tensor coupling and the non-relativistic solution are obtained. The energy spectrum for various levels is presented for several κ values under the condition of exact spin symmetry in the presence or absence of tensor coupling.     

Hypothesis ofP-odd contribution to the gravitational interactions and its consequences

A generalized Lagrangian of spinor particles in a gravitational field containingP-odd terms is proposed. It is used to obtain a quasirelativistic equation of spinors in the field of a gravitational source with nonvanishing intrinsic angular momentum in both an inertial frame and in a frame rotating with the source. For these cases the quasirelativistic Hamiltonian of a test body with nonzero intrinsic angular momentum is obtained in the classical limit; it is shown that the presence in the Hamiltonian ofP-odd terms leads to the appearance of forces that, depending on the orientation of the intrinsic angular momentum of the test body, are attractive or repulsive. It is noted that theC noninvariance of the theory can in principle result in an evolution of the universe in which particles predominate over antiparticles. Other macroscopic consequences whose experimental verification would yield information about the values of the constants introduced in the theory are noted.Moscow State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 91, No. 2, pp. 309–319, May, 1992.     

Reparameterization-Invariant Reduction in the Hamiltonian Description of a Relativistic String

We study the time-reparameterization-invariant dynamics of an open relativistic string using the generalized Dirac–Hamilton theory and resolving the constraints of the first kind. The reparameterization-invariant evolution variable is the time coordinate of the string center of mass. Using a transformation that preserves the diffeomorphism group of the generalized Hamiltonian and the Poincaré covariance of the local constraints, we segregate the center-of-mass coordinates from the local degrees of freedom of the string. We identify the time coordinate of the string center of mass and the proper time measured in the string frame of reference using the Levi-Civita–Shanmugadhasan canonical transformation, which transforms the global constraint (the mass shell) in the new momentum such that the Hamiltonian reduction does not require the corresponding gauge condition. Resolving the local constraints, we obtain an equivalent reduced system whose Hamiltonian describes the evolution w.r.t. the proper time of the string center of mass. The Röhrlich quantum relativistic string theory, which includes the Virasoro operators L _n only with n > 0, is used to quantize this system. In our approach, the standard problems that appear in the traditional quantization scheme, including the space–time dimension D = 26 and the tachyon emergence, arise only in the case of a massless string, M ² = 0.     

Deformable Asymmetric Tops under Similarity Transformations

In this paper the configurations of relative equilibrium are determined for a deformable heavy top with a fixed point constrained to deform only by similarity transformations. We analyze the nonlinear orbital stability using the reduced energy–momentum method for configurations such that the center of the mass vector is parallel to the axis of gravity and coincides with an eigenvector of the Euler tensor. In addition, we study these conditions of stability for a specific deformable top given by a hyperelastic material of the Saint Venant–Kirchhoff type, and describe how these conditions are particularized in the special case of almost rigid tops.     

Some identities for the integro-differential equations describing quasiparticles on an isoenergetic surface

The equations describing quasiparticles that correspond to classical self-consistent fields are reduced to a form symmetric with respect to an indefinite metric.Translated fromMatematicheskie Zametki, Vol. 60, No. 5, pp. 692–707, November, 1996.This research was supported by the Russian Foundation for Basic Research under grant No. 96-01-01544.     

Wannier Representation for the Three-Band Hubbard Model

We obtain the cell representation for the Hamiltonian of the d–p model. We use the Wannier orbitals for the holes belonging to the copper and oxygen ions; the orbitals are orthogonalized on the sites of the copper lattice. The first stage of calculating is diagonalizing the kinetic energy of the oxygen holes and, on this basis, introducing two diagonalizing orbitals for the oxygen fermions. These last two modes have significantly different local energies, which noticeably affect the results in the theory. The obtained Hamiltonian is represented as the sum of a main local term and a perturbation defining the delocalization of the Wannier fermions. We find the low-lying states and the corresponding energy spectrum for the local Hamiltonian. We show that introducing the diagonalizing fermions causes a significant lowering of the energy of the Zhang–Rice singlet.     

Semiscalar equivalence and the factorization of polynomial matrices

One considers the problem of the factorization of polynomial matrices over an arbitrary field in connection with their reducibility by semiscalar equivalent transformations to triangular form with the invariant factors along the principal diagonal. In particular, one establishes a criterion for the representability of a polynomial matrix in the form of a product of factors (the first of which is unital), the product of the canonical diagonal forms of which is equal to the canonical diagonal form of the given matrix. There is given also a method for the construction of such factorizations.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 5, pp. 644–649, May, 1990.     

Casimir effect in nonstationary regions with Friedmann metric

A study is made of the two-dimensional problem of finding the energy-momentum tensor of a scalar massless field with symmetric nonstationary boundary conditions in the case of a nonstationary Friedmann metric. A combined method is proposed for regularizing the energy-momentum tensor — point splitting and Abel-Plana summation. A method is proposed for determining the wave functions and energy-momentum tensor when boundary conditions are specified on characteristics. The solution of these problems in two-dimensional spacetime makes it possible to obtain explicit expressions for the energy-momentum tensor.St. Petersburg University of Economics and Finance. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 101, No. 3, pp. 450–457, December, 1994.     

Maximally Superintegrable Gaudin Magnet: A Unified Approach

A classical integrable Hamiltonian system is defined by an Abelian subalgebra (of suitable dimension) of a Poisson algebra, while a quantum integrable Hamiltonian system is defined by an Abelian subalgebra (of suitable dimension) of a Jordan–Lie algebra of Hermitian operators. We propose a method for obtaining large Abelian subalgebras inside the tensor product of free tensor algebras, and we show that there exist canonical morphisms from these algebras to Poisson algebras and Jordan–Lie algebras of operators. We can thus prove the integrability of some particular Hamiltonian systems simultaneously at both the classical and the quantum level. We propose a particular case of the rational Gaudin magnet as an example.