The Faddeev equation and the location of the essential spectrum of a model multi-particle operator

In this paper we consider a model operator which acts in a three-particle cut subspace of the Fock space. We describe “two-particle” and “three-particle” branches of the essential spectrum and obtain an analog of the Faddeev equation for eigenfunctions of this operator.     

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.     

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.     

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.     

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.     

AnS-matrix regularization of the trace formula for a three-particle system

A regularized trace formula is derived which expresses the trace of the connected part of the resolvent for a three-particle system in terms of the scattering matrices for two- and three-particle systems. This relation allows us to express the third cluster integral for Boltzmann statistics in terms ofS -matrices.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 63, pp. 95–131, 1976.In conclusion, the author would like to express his deep gratitude to V. S. Buslaev and L. D. Faddeev for many fruitful discussions.     

Spectral properties of a Hamiltonian of a four-particle system on a lattice

We consider the Hamiltonian of a system of four arbitrary quantum particles with two-particle contact (noncompact) interaction potentials on a three-dimensional lattice perturbed by three-particle contact potentials. We describe the location of the essential spectrum of the Schrödinger operator corresponding to a four-particle system.     

Point interactions in the problem of three quantum particles with internal structure

A system of three quantum particles with internal structure in which the two-body interactions are point interactions and are described in terms of two-channel Hamiltonians is considered. It is established that in the cases when the parameters of the model are such that the total Hamiltonian of the three-particle system is semibounded the Faddeev equations are Fredholm equations. Boundary conditions are formulated for the differential Faddeev equations whose solutions are the scattering wave functions.Joint Institute for Nuclear Research, Dubna. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 102, No. 2, pp. 258–282, February, 1995.     

Essential spectrum of a model operator associated with a three-particle system on a lattice

We consider a model operator H associated with the system of three particles interacting via nonlocal pair potentials on a ν-dimensional lattice. We identify channel operators and use their spectra to describe the position and structure of the essential spectrum of H. We obtain an analogue of the Faddeev equation for the eigenfunctions of H.     

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.     

Three-particle Coulomb on-shell vertex functions. Behavior of the amplitude for simultaneous transfer of two charged particles in the vicinity of the nearest singularity in cos θ

The connection between the on-shell vertex function (OSVF) and the asymptotic normalized coefficient of the three-particle wave function of the bound system in the configuration space is found. The explicit form of the leading singular term of the OSVF and its Faddeev component for decay of the three-particle bound state into three charged particles is established. An expression is found for the leading singular term of the exact (in the model of four charged particles) amplitude of sub-Coulomb binary reactions in the vicinity of the nearest singularity.Institute of Nuclear Physics, Uzbek Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 94, No. 3, pp. 448–462, March, 1993.     

Finiteness of the discrete spectrum of the three-particle schrödinger equation on a lattice

Consideration is given to the Hamiltonian of a system of three identical quantum particles on a lattice that interact via pairwise contact attractive potentials. Finiteness of the three-particle bound states is proved for the three-dimensional discrete Schrödinger operator on the condition that the operators describing the two-particle subsystems have no virtual levels. For high dimensions (v ≥ 5), the finiteness of three-particle bound states is also proved in the presence of virtual levels.     

Spectrum of the three-particle Schr?dinger operator on a one-dimensional lattice

We consider a system of three arbitrary quantum particles on a one-dimensional lattice interacting pairwise via attractive contact potentials. We prove that the discrete spectrum of the corresponding Schr?dinger operator is finite for all values of the total quasimomentum in the case where the masses of two particles are finite. We show that the discrete spectrum of the Schr?dinger operator is infinite in the case where the masses of two particles in a three-particle system are infinite.     

Spectrum of a Model Operator in the Perturbation Theory of the Essential Spectrum

We consider a model operator acting in a subspace of a Fock space and obtain a symmetrized analogue of the Faddeev equation. For the operator considered, we describe the position and the structure of its essential spectrum.__________Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 3, pp. 544–554, September, 2005.     

Formula for the number of eigenvalues of a three-particle Schrödinger operator on a lattice

We consider a system of three arbitrary quantum particles on a three-dimensional lattice that interact via short-range attractive potentials. We obtain a formula for the number of eigenvalues in an arbitrary interval outside the essential spectrum of the three-particle discrete Schrödinger operator and find a sufficient condition for the discrete spectrum to be finite. We give an example of an application of our results.     

The Efimov effect for a model “three-particle” discrete Schrödinger operator

We study the existence of an infinite number of eigenvalues for a model “three-particle” Schrödinger operator H. We prove a theorem on the necessary and sufficient conditions for the existence of an infinite number of eigenvalues of the model operator H below the lower boundary of its essential spectrum.     

The essential spectrum of the three-particle discrete operator corresponding to a system of three fermions on a lattice

We consider a family of three-particle discrete Shrödinger operators H _μ (K). These operators are associated with the Hamiltonian for a system of three identical particles (fermions) with pairwise two-particle interactions on neighboring junctions of the d-dimensional lattice Z ^d . We describe the location and the structure of the essential spectrum of the operator H _μ (K) for all values of the three-particle quasi-momentum K ∈ T ^d and the interaction energy μ > 0.     

Spectrum of the Three-Particle Schrödinger Difference Operator on a Lattice

For a three-particle operator on a lattice, we study the properties of its spectrum that depend on pairwise interactions and are determined by a parameter characterizing the intensity of interaction.     

Spectrum of a model three-particle Schrödinger operator

We study the spectrum of a model three-particle Schrödinger operator H(ε), ε > 0. We prove that for a sufficiently small ε > 0, this operator has no bound states and no two-particle branches of the spectrum. We also obtain an estimate for the small parameter ε.