Metric Properties of Bogoliubov Trajectories in Statistical Equilibrium Theory

We investigate some properties of the Bogoliubov measure that appear in statistical equilibrium theory for quantum systems and establish the nondifferentiability of the Bogoliubov trajectories in the corresponding function space. We prove a theorem on the quadratic variation of trajectories and study the properties implied by this theorem for the scale transformations. We construct some examples of semigroups related to the Bogoliubov measure. Independent increments are found for this measure. We consider the relation between the Bogoliubov measure and parabolic partial differential equations.     

Some asymptotic formulas for the Bogoliubov gaussian measure

We consider problems of integrating over the Bogoliubov measure in the space of continuous functions and obtain asymptotic formulas for one class of Laplace-type functional integrals with respect to the Bogoliubov measure. We also prove related asymptotic results concerning large deviations for the Bogoliubov measure. For the basic functional, we take the Lp norm and establish that the Bogoliubov trajectories are Höldercontinuous of order γ < 1/2.     

Derivation of the Hydrodynamic Equations in the Framework of the Bogoliubov Functional Hypothesis

We generalize the Bogoliubov functional hypothesis to the case of multiparticle interaction depending on both the coordinates and momenta of particles. We illustrate this with the examples of two weakly relativistic models: the Darwin model in the theory of charged particles and the Fock model in the general theory of relativity. For these models, based on the chain of the BBGKY equations, we calculate weakly relativistic corrections to the classical transport coefficients and find the conditions under which there is no bijective relation between the parameters of the local equilibrium distribution and the hydrodynamic variables.     

Construction of a perturbatively correct light-front Hamiltonian for a (2+1)-dimensional gauge theory

We discuss a perturbation theory on the light front regularized by a method analogous to Pauli–Villars regularization for the (2+1)-dimensional SU(N)-symmetric gauge theory. This allows constructing a correct renormalized light-front Hamiltonian.     

V. A. Fock and N. N. Bogoliubov and their role in establishing modern quantum field theory

The relation between the Wightman axioms in quantum field theory and the “S-matrix” Bogoliubov axioms is discussed. The choice of the Fock representation of the canonical commutation relations for asymptotic field variables is interpreted as a condition for the correct formulation of the relativistic scattering problem. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 120, No. 3, pp. 380–393, September, 1999.     

Contour-ordered Green’s functions in stochastic field theory

We briefly review the functional formulation of the perturbation theory for various Green’s functions in quantum field theory. In particular, we discuss the contour-ordered representation of Green’s functions at a finite temperature. We show that the perturbation expansion of time-dependent Green’s functions at a finite temperature can be constructed using the standard Wick rules in the functional form without introducing complex time and evolution backward in time. We discuss the factorization problem for the corresponding functional integral. We construct the Green’s functions of the solution of stochastic differential equations in the Schwinger-Keldysh form with a functional-integral representation with explicitly intertwined physical and auxiliary fields.     

Perturbation theory in the neighborhood of extended objects

Using a unitary mapping to the “action-angle” variables, we formulate the perturbation theory with respect to the inverse coupling constant in the neighborhood of a nontrivial critical point of the action. We also describe the standard perturbation theory in this neighborhood. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 123, No. 3, pp. 433–451, June, 2000.     

Perturbation theory in large order

For many quantum mechanical models, the behavior of perturbation theory in large order is strikingly simple. For example, in the quantum anharmonic oscillator, which is defined by−″ + (x²/4+εx⁴/4−E)y=0, y(±∞)=0,the perturbation coefficients A_n in the expansion for the ground-state energysimplify dramatically as n → ∞:.We use the methods of applied mathematics to investigate the nature of perturbation theory in quantum mechanics and we show that its large-order behavior is determined by the semiclassical content of the theory. In quantum field theory the perturbation coefficients are computed by summing Feynman graphs. We present a statistical procedure in a simple λ⁴ model for summing the set of all graphs as the number of vertices → ∞. Finally, we discuss the connection between the large-order behavior of perturbation theory in quantum electrodynamics and the value of α, the charge on the electron.     

Lifted inequalities for 0-1 mixed integer programming: Basic theory and algorithms

We study the mixed 0-1 knapsack polytope, which is defined by a single knapsack constraint that contains 0-1 and bounded continuous variables. We develop a lifting theory for the continuous variables. In particular, we present a pseudo-polynomial algorithm for the sequential lifting of the continuous variables and we discuss its practical use.This research was supported by NSF grants DMI-0100020 and DMI-0121495Mathematics Subject Classification (2000): 90C11, 90C27     

On Blowup for Time-Dependent Generalized Hartree–Fock Equations

We prove finite-time blowup for spherically symmetric and negative energy solutions of Hartree–Fock and Hartree–Fock–Bogoliubov-type equations, which describe the evolution of attractive fermionic systems (e.g. white dwarfs). Our main results are twofold: first, we extend the recent blowup result of Hainzl and Schlein (Comm. Math. Phys. 287:705–714, 2009) to Hartree–Fock equations with infinite rank solutions and a general class of Newtonian type interactions. Second, we show the existence of finite-time blowup for spherically symmetric solutions of a Hartree–Fock–Bogoliubov model, where an angular momentum cutoff is introduced. We also explain the key difficulties encountered in the full Hartree–Fock–Bogoliubov theory.     

Nonstationary polaron

We define the Bogoliubov group variables for the space-time translations in the secondarily quantized system. We propose a scheme for quantizing a scalar field that has a nonzero classical component and interacts with a charged scalar field. The polaron is treated as a result of the interaction of the charged particle with the classical component of the neutral field. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 122, No. 3, pp. 417–425, March, 2000.     

positivity in time dependent linear transport theory

We present methods using positive semigroups and perturbation theory in the application to the linear Boltzmann equation. Besides being a review, this paper also presents generalizations of known results and develops known methods in a more abstract setting.In Section 1 we present spectral properties of the semigroup operatorsW _a(t) of the absorption semigroup and its generatorT _a. In Section 2 we treat the full semigroup (W(t);t0) as a perturbation of the absorption semigroup. We discuss part of the problems (perturbation arguments and existence of eigenvalues) which have to be solved in order to obtain statements about the large time behaviour ofW(·). In Section 3 we discuss irreducibility ofW(·).In four appendices we present abstract methods used in Sections 1, 2 and 3.     

Asymptotics of small deviations of the Bogoliubov processes with respect to a quadratic norm

We obtain results on small deviations of Bogoliubov’s Gaussian measure occurring in the theory of the statistical equilibrium of quantum systems. For some random processes related to Bogoliubov processes, we find the exact asymptotic probability of their small deviations with respect to a Hilbert norm.     

On the microscopic origin of integrability in the Seiberg-Witten theory

We discuss the microscopic origin of integrability in the Seiberg-Witten theory. In particular, we discuss the theory in more detail with the simplest higher perturbation in the ultraviolet, where additional explicit results are obtained using bosonization and elliptic uniformization of the spectral curve. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 154, No. 3, pp. 424–450, March, 2008.     

Theory of superfluidity in a polariton system

We consider the superfluidity properties of a two-dimensional system of polaritons in an optical cavity. Deriving an expression for the effective low-energy action for thermodynamic phase fluctuations, we simultaneously obtain the expression for an analogue of superfluid density in the system in terms of the current-current correlation function and also find the expression for the current operator. We describe the Bogoliubov approximation for a polariton system and calculate the superfluid density. We discuss the Berezinskii-Kosterlitz-Thouless transition in the system under study. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 154, No. 2, pp. 372–384, February, 2008.     

Dynamics near relative equilibria: Nongeneric momenta at a 1:1 group-reduced resonance

An interesting situation occurs when the linearized dynamics of the shape of a formally stable Hamiltonian relative equilibrium at nongeneric momentum 1:1 resonates with a frequency of the relative equilibrium's generator. In this case some of the shape variables couple to the group variables to first order in the momentum perturbation, and the first order perturbation theory implies that the relative equilibrium slowly changes orientation in the same way that a charged particle with magnetic moment moves on a sphere under the influence of a radial magnetic monopole. In the course of showing this a normal form is constructed for linearizations of relative equilibria and for Hamiltonians near group orbits of relative equilibria. Received August 27, 1998; in final form February 20, 1999     

<Emphasis Type="Italic">p</Emphasis>-adic renormalization group solutions and the euclidean renormalization group conjectures

We discuss algebraic similarity of the Wilson’s renormalization groups in the Euclidean and p-adic spaces. Automodel Hamiltonians have identical form in both cases in the framework of perturbation theory. Fermionic p-adic model has exact renormalization group solution which generates a list of non-trivial conjectures for the Euclidean case.     

Asymptotic behavior of small deviations for Bogoliubov’s Gaussian measure in the L p norm, 2 ≤ p ≤ ∞

We prove several results on exact asymptotic formulas for small deviations in the L^p-norm with 2 ～ p ～ ∞ for Bogoliubov’s stationary Gaussian process ξ(t). We prove the property of mutual absolute continuity for the conditional Bogoliubov measure and the conditional Wiener measure and calculate the Radon-Nikodym derivative.