﻿ Calogero Model with Different Masses

Open Journal of Microphysics
Vol.3 No.3(2013), Article ID:35704,4 pages DOI:10.4236/ojm.2013.33011

Calogero Model with Different Masses

Ancilla Nininahazwe

Université du Burundi, Institut de Pédagogie Appliquée, Bujumbura, Burundi

Email: nininaha@yahoo.fr

Copyright © 2013 Ancilla Nininahazwe. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received May 15, 2013; revised June 15, 2013; accepted June 22, 2013

Keywords: Multispecies One-Dimensional Calogero; Equal Masses; Different Masses; Usual Calogero Model

ABSTRACT

We study a multispecies one-dimensional Calogero model with twoand three-body interactions. Here, we factorize the ground state out of the Hamiltonian H in order to get the new operator which preserves some spaces of polynomials in the case of equal masses, i.e. (the usual Calogero model) and in the case with different masses. The spectrum of these both cases is found easily.

1. Introduction

The ordinary Cologero [1,2] model describes N indistinguishable particles on the line which interact through an inverse-square two-body interaction. The model is completely integrable in both the classical and quantum case . The spectrum is known and the wave functions are given implicitly. In the present paper, which is in a sense a continuation of the investigation of the ordinary model , we use an algebraic method to find some of the salient features of the multispecies Calogero model on the line with twoand three-body interactions. After performing a certain transformation of the operator H, we get a new Hamiltonian for which we find its spectrum in the both cases with equal masses and different masses.

2. Calogero Model with Different Masses

In this section, we reconsider the “multispecies” Calogero model considered in . The Hamiltonian reads (1)

where .

We factorize the full ground state (2)

with (3) (4)

When factorizing the factor out of H, we got the new operator (5) (6)

The operator preserves some spaces of polynomials that we would like to study and compare with the invariant spaces available in the case of equal masses, i.e. (the usual Calogero model). We first proceed with the i.e. two body case. Then it is easy to check that the following vector spaces are preserved by : (7)

with (8)

It should be stressed that the combination has to be eliminated from because it is not preserved by the part (9)

of the operator . As a consequence the monomial has to be discarded from P3 since i.e, the following part of the operator  (10)

would naturally involve a term of the form in the first order monomial which is excluded by the above argument (i.e. ). Proceeding along the same lines we conclude that the set of spaces can be rephased in terms of the vector spaces defined in i.e.  (11)

with is the center-of-mass coordinate and (12)

in this respect, the operator H (and then also ) is integrable and solvable for N = 2.

Notice that the space is equivalent to the ones considered by , apart from the fact that the variable (the analogue of ) is defined with the masses.

Let us now investigate the case N = 3. Again we can show that the following vector spaces are preserved by the operator , (13)

where (14)

Note that above is the generalization of the variable of . However, it turns out to be impossible to construct a translation invariant-cubic polynomial of the form (15)

which is preserved by the operator if the masses mi are generic (i.e , etc). As a consequence, the dimension of the vector spaces of monomials preserved by is lower than the vector spaces preserved by and the number of algebraic eigenvalues is lower than the usual Calogero case. In the next, this can be demonstrated easily in the particular case N = 2.

2.1. Eigenvalues for the Case with Equal Masses

We use the operator (16) (17) (18) (19)

The spectrum for the above case is 0;

1, 2;

2, 3, 4.

2.2. Eigenvalues for the Case with Different Masses

In this case we apply the some procedure used in the previous case (i.e. we consider also N = 2) but the operator D has the following form (20) (21) (22) (23)

The spectrum for the above case is 0;

1;

2, 2.

More generally, the vector spaces preserved by are of the form (24)

and any eigenvector of can be written according to (25)

while the corresponding eigenvalues are given by (26)

so that the spectrum of consists of integers of the form (27)

as generic in . In this way, we have redemonstrated the result of these authors by following the algebraic technique of operators preserving spaces of monomials as suggested by .

We have attempted to construct invariant spaces of polynomials involving the monomials (28)

with . These polynomials are indeed such that is a polynomial but the new polynomials are not in general expressible as polynomials of the two variables X and (i.e. ). More generally, the polynomials for body can be written as follows (29)

3. Conclusion

Here we have constructed the operator which preserves some spaces of polynomials and compared with the invariant spaces available in the usual Calogero model ( i.e. the masses are equal). We have determined the real spectrum for the case with different masses and for the case for equal masses where i.e. two body case. This extended Calogero model exhibits some remarkable properties which are absent in the case of usual Calogero model. For example, the number of eigenvalues in the case with different masses is lower than one of eigenvalues of the usual Calogero model.

4. Acknowledgements

I thank Pr. Yves Brihaye for useful discussions

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