A well-known problem with the many-body approximations for interacting condensed bosons is the dichotomy between the "conserving" and "gapless" approximations, which either obey the conservations laws or satisfy the Hugenholtz-Pines condition for a gapless excitation spectrum, in the order. It is here shown that such a dichotomy does not exist for a system of composite bosons, which form as bound-fermion pairs in the strong-coupling limit of the fermionic attraction. By starting from the constituent fermions, for which conserving approximations can be constructed for any value of the mutual attraction according to the Baym-Kadanoff prescriptions, it is shown that these approximations also result into a gapless excitation spectrum for the boson-like propagators in the broken-symmetry phase.

STRINATI CALVANESE, G., PIERI, P. (2005). Conserving and gapless approximations for the composite bosons in terms of the constituent fermions. EUROPHYSICS LETTERS, 71(3), 359-365 [10.1209/epl/i2005-10097-y].

Conserving and gapless approximations for the composite bosons in terms of the constituent fermions

PIERI, Pierbiagio
2005

Abstract

A well-known problem with the many-body approximations for interacting condensed bosons is the dichotomy between the "conserving" and "gapless" approximations, which either obey the conservations laws or satisfy the Hugenholtz-Pines condition for a gapless excitation spectrum, in the order. It is here shown that such a dichotomy does not exist for a system of composite bosons, which form as bound-fermion pairs in the strong-coupling limit of the fermionic attraction. By starting from the constituent fermions, for which conserving approximations can be constructed for any value of the mutual attraction according to the Baym-Kadanoff prescriptions, it is shown that these approximations also result into a gapless excitation spectrum for the boson-like propagators in the broken-symmetry phase.
2005
STRINATI CALVANESE, G., PIERI, P. (2005). Conserving and gapless approximations for the composite bosons in terms of the constituent fermions. EUROPHYSICS LETTERS, 71(3), 359-365 [10.1209/epl/i2005-10097-y].
STRINATI CALVANESE, Giancarlo; PIERI, Pierbiagio
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/864194
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