No data available.

Please log in to see this content.

You have no subscription access to this content.

No metrics data to plot.

The attempt to load metrics for this article has failed.

The attempt to plot a graph for these metrics has failed.

The full text of this article is not currently available.

Exactly Solvable Many‐Boson Model

### Abstract

A many‐boson model is formulated and expressions for its exact eigenstates and energies are obtained for both an arbitrary finite and an infinite number of bosons. The Hamiltonian of the model contains interactions between bosons whose momenta have equal magnitudes but opposite directions. The matrix elements of this interaction are taken to be a constant over a range of momenta surrounding **k** = 0. The ground state of the 2*N*‐particle system is shown to be a product of *N* pair‐creation operators acting on the vacuum state. Each of these pair‐creation operators depends upon one of *N* parameters which are called pair energies. The *N* pair energies are shown to satisfy a coupled system of nonlinear algebraic equations. The energy of the state is the sum of the pair energies and the occupation probabilities of the single‐particle levels are given as simple functions of the pair energies. Similar results are derived for the excited states of the system and for the states of an odd number of particles. These results are valid for both a repulsive and an attractive interaction, since they only depend upon the form of the interaction. The equations are solved algebraically for two modelsystems. The first of these is one whose single‐particle kinetic energy takes on only one value. The equations for this system are solved for an arbitrary interaction strength and it is shown that the pair energies are proportional to the zeros of certain Laguerre polynomials. The second system is one in which the single‐particle kinetic energy can take on two values. The equations for this system are solved in the strong repulsive‐interaction limit and it is shown that the pair energies are proportional to the zeros of certain Jacobi polynomials. The excitation energies of this second system are shown to be proportional to 1/*n* and the occupations of the two single‐particle levels in the ground state are shown to be proportional to *n*, where *n* is the total number of particles. For a repulsive interaction and an arbitrary single‐particle spectrum, the algebraic equations for the pair energies are converted into an approximate integral equation for the density of roots which is accurate to order 1/*n*. This integral equation is solved for a strong interaction which, in the context of this model, means an interaction whose strength is greater than a constant times 1/*V* ^{⅔} in the limit of a large volume. From this solution, the following results are obtained: (1) the lowest two single‐particle levels have occupations of order *n*; (2) the excitation spectrum is that of a set of noninteracting quasiparticles; and (3) the quasiparticle spectrum has two zeros corresponding to the lowest two single‐particle levels. Apart from the presence of two zeros, the quasiparticle spectrum does not differ significantly from that of the noninteracting particles.

© 1968 The American Institute of Physics

Received 16 October 1967
Published online 28 October 2003

/content/aip/journal/jmp/9/9/10.1063/1.1664719

http://aip.metastore.ingenta.com/content/aip/journal/jmp/9/9/10.1063/1.1664719

Article metrics loading...

/content/aip/journal/jmp/9/9/10.1063/1.1664719

2003-10-28

2016-10-27

Full text loading...

###
Most read this month

Article

content/aip/journal/jmp

Journal

5

3

Commenting has been disabled for this content