Stability of Three-Body Bound States on the Light Front

We investigate the stability of the relativistic three-boson system with a zero-range force in the light-front form. In particular, we study the dependence of the system on an invariant cut-off. We discuss the conditions for the relativistic Thomas collapse. Finally, we fix the parameters of the model introducing a scale.Received February 2, 2003; accepted May 30, 2003 Published online September 24, 2003     

The Stability of the Relativistic Three-Body System and In-Medium Equations

We present a relativistic three-body equation to study the stability of the isolated three-body system and the correlations in a medium of finite temperatures and densities. Relativity is implemented utilizing the light-front form. Using a zero-range force we find the relativistic analog of the Thomas collapse and investigate the possibility that the nucleon exists as a Borromean system. Within a systematic Dyson equation approach we calculate the three-body Mott transition and the critical temperature of the color-superconducting phase.     

Critical Stability of Three-Body Relativistic Bound States with Zero-Range Interaction

For the zero-range interaction providing a given mass M₂ of the two-body bound state, the mass M₃ of the relativistic three-body system is calculated. We have found that the three-body system exists only when M₂ is greater than a critical value M_c ( 1.43 m for bosons and 1.35 m for fermions, m being the constituent mass). For M₂=M_c the mass M₃ turns into zero and for M₂ < M_c there is no solution with real value of M₃.     

Stability and Chaos of Two Coupled Bose-Einstein Condensates with Three-Body Interaction

We study the dynamics of two Bose-Einstein condensates （BECs） tunnel-coupled by a double-well potential. A real three-body interaction term is considered and a two-mode approximation is used to derive two coupled equations, which describe the relative population and relative phase. By solving the equations and analyzing the stability of the system, we find the stable stationary solutions for a constant atomic scattering length. When a periodically time- varying scattering length is applied, Melnikov analysis and numerical calculation demonstrate the existence of chaotic behavior and the dependence of chaos on the three-body interaction parameters.     

Stability and Chaos of Two Coupled Bose-Einstein Condensates with Three-Body Interaction

We study the dynamics of two Bose-Einstein condensates (BECs) tunnel-coupled by a double-well potential.A real three-body interaction term is considered and a two-mode approximation is used to derive two coupled equations,which describe the relative population and relative phase. By solving the equations and analyzing the stability of the system, we find the stable stationary solutions for a constant atomic scattering length. When a periodically time-varying scattering length is applied, Melnikov analysis and numerical calculation demonstrate the existence of chaotic behavior and the dependence of chaos on the three-body interaction parameters.     

Stability of Three-Body Coulomb Systems with J = 1 in the Oscillator Representation

The oscillator representation is applied to calculate the energy spectrum of three-body Coulomb systems with total angular momentum ^J. For three-body Coulomb systems with J = 1 and arbitrary masses the region of stability is determined. For the systems (A ⁺ A ⁻ e ⁻), (pe ⁻ C ⁺), (pB ⁻ e ⁻), and (D ⁺ e ⁻ e ⁺), the values of the critical masses of the particles A, B, C, and D are obtained as m _A = 2.22m _e , m _B = 1.49m _e , m _C = 2.11m _e and m _D = 4.15m _e . Received November 6, 1995; received December 4, 1995; accepted for publication January 22, 1996     

Model Study of Three-Body Forces in the Three-Body Bound State

The Faddeev equation for the three-body bound state with two- and three-body forces is solved directly as three-dimensional integral equation. The numerical feasibility and stability of the algorithm, which does not employ partial wave decomposition is demonstrated. The three-body binding energy and the full wave function are calculated with Malfliet-Tjon-type two-body potentials and scalar two-meson exchange three-body forces. For two- and three- body forces of ranges and strengths typical of nuclear forces the single-particle momentum distribution and the two-body correlation function are similar to the ones found for realistic nuclear forces.     

On Action-Minimizing Retrograde and Prograde Orbits of the Three-Body Problem

A retrograde orbit of the planar three-body problem is a relative periodic solution with two adjacent masses revolving around each other in one direction while their mass center revolves around the third mass in the other direction. The orbit is said to be prograde or direct if both revolutions follow the same direction. Let T > 0 and be fixed, and consider the rotating frame which rotates the inertia frame about the origin with angular velocity . In a recent work of K.-C.Chen [5], the existence of action-minimizing retrograde orbits which are T-periodic on this rotation frame were proved to exist for a large class of masses and a continuum of . In this paper we generalize the main result in [5], provide some quantitative estimates for admissible masses and mutual distances, and show miscellaneous examples of action-minimizing retrograde orbits. We also show the existence of some prograde and retrograde solutions with additional symmetries.     

On a Three-Body Problem in Relativistic Quantum Mechanics

Proceeding from the method of packing operators developed by Sokolov and from the “light front variables” technique, the explicit formulae for packing operators and auxiliary mass operators for a system of three particles with arbitrary spins are derived. It is shown that for the packing operators there exists an infinite number of solutions yielding different physical consequences. The problem of the theory substantiation is discussed; the arguments in favour of a certain choice of packing operators are produced.     

On the Uniqueness of the Solution to the Three-Body Problem with Zero-Range Interactions

We consider the uniqueness of the solution to a three-body problem with zero-range Skyrme interactions in configuration space. With the lowest, k⁰, two-body term alone the problem is known to have no unique solution as the system collapses – the variational estimate of the energy tends towards negative infinity, the size of the system towards zero. We argue that the next, k², two-body term removes the collapse and the three-body system acquires finite ground-state energy and size. The three-body interaction term is thus not necessary to provide a unique solution to the problem.     

Collapse to the Center and Ambiguity in the Asymptotic Behavior of the Off-Shell Scattering Amplitude in Singular Three-Body Problems

Some examples of equations for the there-body problem where there is an oscillating high-momentum behavior are discussed. Specifically, these are (i) the equation in the fixed-center approximation; (ii) the unitarized equation in the fixed-center approximation; (iii) the Skornyakov–Ter-Martirosyan equation; and (iv) equations involving operators that are used in effective field theory—that is, those that are expandable in positive-power series in momentum. It is shown that, in such problems, there arises a situation analogous to a collapse to the center—that is, an infinite number of bound states. The energy of these states is unbounded from below. In this sense, the situation in the models being considered is close to a collapse to the center in the two-body problem.     

Stability and Collective Excitation of Two-Dimensional BECs with Two- and Three-Body Interactions in an Anharmonic Trap

The stability and collective excitation of Bose-Einstein condensates with both two- and three-body interactions in a two-dimensional anhaxmonic trap （i.e., harmonic plus quartic trap） are investigated. By using the variational method, the influence of the three-body interaction and the anharmonicity on the stability axe discussed in detail. It is found that the anhaxmonicity of the trap and the three-body interaction have significant effect on the stability and collective excitations of the system.     

Manifestation of Three-Body Forces in Three-Body Bethe–Salpeter and Light-Front Equations

Bethe–Salpeter and light-front bound state equations for three scalar particles interacting by scalar exchange-bosons are solved in ladder truncation. In contrast to two-body systems, the three-body binding energies obtained in these two approaches differ significantly from each other: the ladder kernel in light-front dynamics underbinds by approximately a factor of two compared to the ladder Bethe–Salpeter equation. By taking into account three-body forces in the light-front approach, generated by two exchange-bosons in flight, we find that most of this difference disappears; for small exchange masses, the obtained binding energies coincide with each other.     

A General T-Matrix Approach Applied to Two-Body and Three-Body Problems in Cold Atomic Gases

We propose a systematic T-matrix approach to solve few-body problems with s-wave contact interactions in ultracold atomic gases. The problem is generally reduced to a matrix equation expanded by a set of orthogonal molecular states, describing external center-of-mass motions of pairs of interacting particles; while each matrix element is guaranteed to be finite by a proper renormalization for internal relative motions. This approach is able to incorporate various scattering problems and the calculations of related physical quantities in a single framework, and also provides a physically transparent way to understand the mechanism of resonance scattering. For applications, we study two-body effective scattering in 2D–3D mixed dimensions, where the resonance position and width are determined with high precision from only a few number of matrix elements. We also study three fermions in a (rotating) harmonic trap, where exotic scattering properties in terms of mass ratios and angular momenta are uniquely identified in the framework of T-matrix.     

Reduction of Relativistic Three-Body Kinematics

The Klein—Gordon system describing three scalar particles without interaction is cast into a new form by transformation of the momenta. Two redundant degrees of freedom are eliminated; we are left with a covariant equation for a reduced wave function with three-dimensional arguments. This new formulation of the mass-shell constraints is equivalent to the original KG system in a sector characterized by positivity of the energies and, if the mass differences are not too large, by a moderately relativistic regime. Introducing mutual interactions provides a model which is (at least for three equal masses) tractable and admits a reasonable nonrelativistic limit.     

Structure of Exotic Three-Body Systems

The classification of large halos formed by two identical particles and a core is systematically addressed according to interparticle distances. The root-mean-square distances between the constituents are described by universal scaling functions obtained from a renormalized zero-range model. Applications for halo nuclei, ¹¹Li and ¹⁴Be, and for atomic ⁴He₃ are briefly discussed. The generalization to four-body systems is proposed.     

Three-Potential Formalism for the Atomic Three-Body Problem

Based on a three-potential formalism we propose mathematically well-behaved Faddeev-type integral equations for the atomic three-body problem and describe their solutions in Coulomb-Sturmian space representation. Although the system contains only long-range Coulomb interactions these equations allow us to reach a solution by approximating only some auxiliary short-range potentials. We outline the method for bound states and demonstrate its power in benchmark calculations. We can report a fast convergence in angular-momentum channels. Received September 30, 1997; accepted in final form January 23, 1998     

On the Relation between Effective Potentials and Realistic Potentials

A velocity dependent effective potential of s- and p-wave interaction denoted by VG2 has been applied to calculate the parameters of nuclear matter. Using this potential, the binding energy of a group of double closed shell nuclei is calculated according to the shell model. Also, the binding energy of ¹²C and ¹⁶O is calculated assuming Brink's model and using the VG2 interaction together with the potential deduced by Arickx et al. Reasonable agreement with experimental data is obtained.