Structure of regular solutions of Faddeev equations near the pair impact point

We study the two-and three-dimensional Faddeev equations for a three-particle system with central or S-wave pair interactions. The regular solutions of such equations are represented as infinite series in integer powers of the distance between two particles and the sought functions of the other three-particle coordinates. Constructing such functions reduces to solving algebraic recurrence relations. We derive the boundary conditions at the pair impact point for the regular solutions of the Faddeev equations. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 1, pp. 112–130, July, 2008.     

Three-Particle Problem with Pairwise Interactions Inversely Proportional to Squared Distance

The hyperharmonic method is used to investigate the three-particle Schrödinger and Faddeev equations with pairwise interactions inversely proportional to the squared distance. Exact solutions for such equations are constructed in the form of a product of the Bessel function depending on the hyperradius and a finite linear combination of the hyperharmonics. A criterion for the existence of such solutions is proved and analyzed.     

Spurious terms in the three-body problem

The method of hyperharmonics is used to split the central two-body interactions and the Faddeev components of the wave function in a three-body system into physical and spurious terms. The sum of the physical terms of the interactions or of the Faddeev components for all pairs of particles is nonzero, whereas the sums of spurious terms of both the interactions and the Faddeev components over all pairs of particles vanish identically. We establish a criterion for the existence of spurious terms. We show that a sufficient condition for this criterion is equivalent to the conservation law for a certain quantum number. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 125, No. 2, pp 253–271, November, 2000.     

Construction of regular solutions of Schrödinger and Faddeev equations in the linear three-particle configuration limit

We study the six-dimensional Schrödinger and Faddeev equations for a three-particle system with central pairwise interactions more general than the Coulomb interactions. The regular general and particular physical solutions of such equations are represented by infinite series in integer powers of the distance from one of the particles to the center of mass of the other two particles and in some functions of the other three-particle coordinates. Constructing such functions in the angular bases formed by spherical and bispherical harmonics or by symmetrized Wigner D-functions reduces to solving simple algebraic recurrence relations. For the projections of physical solutions on the angular basis functions, we introduce the boundary conditions in the linear three-particle configuration limit.     

Extension theory approach to scattering and annihilation in the\bar pd system

We consider the problems of three-particle scattering and annihilation in a system of three strongly interacting charged particles ( pn). We propose a model for the elastic scattering and the breakup process in the nucleon channel as well as for the annihilation into mesons. The mathematical foundation of the model is the extension theory of symmetrical operators. In the framework of this model, we construct the modified integral Faddeev equations with energy-dependent interactions taking the annihilation processes into account. These equations are uniquely resolvable for suitable classes of functions. On this basis, we deduce the corresponding differential Faddeev equations, construct asymptotic boundary conditions for wave function components, and formulate boundary problems for a system composed of nucleonic and mesonic channels. The results obtained are applied to scattering and annihilation processes in the three-particle system . Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 118, No. 1, pp. 74–94, January, 1999.     

Faddeev differential equations as a spectral problem for a nonsymmetric operator

We consider a nonsymmetric matrix operator whose eigenvalue problem is the system of Faddeev differential equations for a three-particle system. For this operator and its adjoint, the resolvents are represented in terms of Faddeev T-matrix components of the three-particle Schrödinger operator. On the basis of these representations, the invariant spaces of the operators under consideration are investigated and their eigenfunctions are determined. The biorthogonality and completeness of the eigenfunction system are proved.We dedicate this paper to the memory of Stanislav Petrovitch Merkuriev, who left us three years ago.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 107, No. 3, pp. 513–528, June, 1996.     

Structure of the resolvent of the Schrödinger operator for a system of three charged particles

Modified integral Faddeev equations for a system of three particles with Coulomb interaction are studied. The structure of the kernel of the resolvent on a continuous spectrum in coordinate space is described.     

Many-Particle and Semiclassical Limit Transitions for Nonrelativistic Bosons in a Quantized Electromagnetic Field

Using the method of the analytic germ, we obtain a system of equations for the amplitudes of one-particle phase densities of a system of several species of classical particles with electromagnetic interaction. The corresponding equations result from an extremely complicated limit transition in the theory of bosons interacting with a quantized electromagnetic field rather than in the classical equations for N particles in a magnetic field. This transition implies a double limit: first, the limit of large numbers of particles and photons and, second, the semiclassical limit. Moreover, in the first of these limits under some additional assumptions, we obtain the equations that are the steady-state conditions for an action functional considered in a recent paper by Faddeev and Niemi.     

A stability result concerning the Shannon entropy

Summary. We are concerned with a well-known characterization of the Shannon entropy by Faddeev, suitably re-examined in the frame of Ulam--Hyers "stability" of functional equations.¶By use of some results about number theoretical functions, we give a sufficient condition that the solutions of a suitable system of countably many functional inequalities approximate the Shannon entropy uniformly.     

Spurious solutions of Faddeev equations with central potentials

Within the limits of the hyperharmonics approach, spurious solutions of the Faddeev differential equations are studied for a system of three distinguishable particles interacting via central potentials. The criterion for the existence of spurious solutions is proved. A straightforward way of constructing explicitly spurious solutions is suggested, and the results are illustrated by examples.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 107, No. 3, pp. 501–512, June, 1996.     

Generalized limiting absorption method and multidimensional inverse scattering theory

We generalize the classical limiting absorption method. This generalization is applied to the study of the Faddeev–Lippmann–Schwinger equations in the Faddeev–Newton approach to multidimensional inverse scattering theory. In particular, we give a new proof, under more general conditions than were known previously, of the absence of exceptional points for small potentials and large values of the parameters, and on the existence of real exceptional points if there are complex ones, in particular for potentials that produce negative eigenvalues.     

Perturbation theory in the scattering problem for a three-particle system

We consider the scattering problem for a system of three nonrelativistic particles in the case of energies below the threshold of the system breakup into three free particles. We assume that the interaction potentials can be represented as a sum of two terms, one of which is a small perturbation. We develop a perturbation theory scheme for solving the scattering problem based on the three-particle Faddeev equations.     

Few-body problem in the boundary condition model and quasipotentials

The boundary condition model is reformulated in terms of singular quasipotentials. In the three-body problem, Fredholm integral equations are constructed for the densities of simple and double layers concentrated on a noncompact surface with edges. Differential equations augmented with two-sided boundary conditions are formulated for the Faddeev and Faddeev—Yakubovskii components of the wave functions of three- and four-body systems.St Petersburg State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 94, No. 3, pp. 435–447, March, 1993.     

On spectral decompositions of solutions to discrete Lyapunov equations

A new approach to solving discrete Lyapunov matrix algebraic equations is based on methods for spectral decomposition of their solutions. Assuming that all eigenvalues of the matrices on the left-hand side of the equation lie inside the unit disk, it is shown that the matrix of the solution to the equation can be calculated as a finite sum of matrix bilinear quadratic forms made up by products of Faddeev matrices obtained by decomposing the resolvents of the matrices of the Lyapunov equation. For a linear autonomous stochastic discrete dynamic system, analytical expressions are obtained for the decomposition of the asymptotic variance matrix of system’s states.     

Global solutions of the evolutionary Faddeev model with small initial data

We consider the Cauchy problem for evolutionary Faddeev model corresponding to maps from the Minkowski space ℝ¹⁺ⁿ to the unit sphere $ \mathbb{S} $ \mathbb{S} ², which obey a system of non-linear wave equations. The nonlinearity enjoys the null structure and contains semi-linear terms, quasi-linear terms and unknowns themselves. We prove that the Cauchy problem is globally well-posed for sufficiently small initial data in Sobolev space.     

Local Hamiltonian in the Faddeev-Tirkkonen model

A lattice Hamiltonian is constructed by means of the factorization technique for the L-operator developed by Faddeev and Tirkkonen. It is shown that the continuum limit of this Hamiltonian leads to equations of motion of the Liouville model. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 335, 2006, pp. 246–254.     

Spectral properties of Faddeev's equations

The spectral properties of the matrix operators corresponding to the three-particle Faddeev equations are investigated. It is shown that these operators have two types of invariant subspace. On the subspaces of the first type, the operators possess an eigenvalue spectrum identical to the spectrum of the three-particle Hamiltonian, while the eigenfunctions can be expressed in terms of solutions of the Schrödinger equation. On the subspaces of the second type, the operators are equivalent to the kinetic-energy operator of the system, and therefore their eigenfunctions do not correspond to the dynamics of the interacting particles.State University, St. Petersburg. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 102, No. 3, pp. 323–336, March, 1995.     

Smooth and convergent ε-approximations of the first boundary-value problem for equations of the Kelvin-Voight and oldroyd fluids

Smooth convergent ε-approximations (11)–(13) for the equations of Oldroyd (8) and Kelvin-Voight (9), (10) fluids are constructed. It is shown that the first initial boundary-value problem for two-dimensional system (11) and three-dimensional systems (12) and (13) for every ε>0 has a unique classical solution, and as ε → 0 these solutions converge to classical solutions of the first initial boundary-value problem for Eqs. (8), (9), and (10) respectively. Bibliography: 10 titles. Dedicated to L. D. Faddeev on the occasion of his 60th birthday Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 215, 1994, pp. 246–255. Translated by O. A. Ivanov.     

Spurious solutions of three-dimensional Faddeev equations

We obtain explicit spurious solutions of three-dimensional Faddeev equations written in the total angular momentum and total space parity representation. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 148, No. 2, pp. 227–242, August, 2006.     

Quantum Floquet functions

The quantum analog of the Floquet solution of the auxiliary linear problem for the lattice model of the nonlinear Schrödinger equation is constructed. Applications to the quantum Gel'fand-Levitan-Marchenko equations are discussed.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 131, pp. 128–141, 1983.The authors are grateful to L. D. Faddeev, P. P. Kulish, E. K. Sklyanin, and M. A. Semenov-Tyan-shanskii for useful and interesting discussions.