Phase diagram for interacting Bose gases

Abstract

We propose a new form of the inversion method in terms of a selfenergy expansion to access the phase diagram of the Bose-Einstein transition. The dependence of the critical temperature on the interaction parameter is calculated. This is discussed with the help of a new condition for Bose-Einstein condensation in interacting systems which follows from the pole of the T-matrix in the same way as from the divergence of the medium-dependent scattering length. A many-body approximation consisting of screened ladder diagrams is proposed which describes the Monte Carlo data more appropriately. The specific results are that a non-selfconsistent T-matrix leads to a linear coefficient in leading order of 4.7, the screened ladder approximation to 2.3, and the selfconsistent T-matrix due to the effective mass to a coefficient of 1.3 close to the Monte Carlo data.

The condition of existence of the Bose–Einstein condensation in the superfluid liquid helium

“…Previously, the authors of reference [10] discovered that, at the lambda transition, there was scattering between atoms of the superfluid liquid helium, which is confirmed by the calculation of the dependence of the critical temperature on the interaction parameter, here the scattering length. This means it is necessary to revise the conditions that determine the Bose-Einstein condensation in the superfluid liquid helium.…”

Bose condensation of squeezed light

“…We will derive the medium-dependent scattering range from solving the Bethe-Salpeter equation which diverges near the phase transition. This method has been used before in [62,67] such that we might present it here only briefly. The Bethe-Salpeter equation for the many-body Tmatrix with a center-of-the-mass momentum K, and incoming and outgoing difference momenta p and p ′ of the two particles, respectively, can be solved…”

Phase diagram and binding energy of interacting Bose gases

“…The two-particle scattering is described with the manybody T matrix in the ladder and quasiparticle approximation, 6 T pp ͑Q,͒ = V pp + ͵ d 3 q…”