Eur. Phys. J. A (2007) 31: 734-738
https://doi.org/10.1140/epja/i2006-10286-2

QNP 2006

Superfluidity in many fermion systems: Exact renormalisation group treatment

School of Physics and Astronomy, The University of Manchester, M13 9PL, Manchester, UK

^* e-mail: krippa@theoserv.phy.umist.ac.uk

Received: 18 December 2006
Accepted: 25 December 2006
Published online: 20 March 2007

Abstract

The application of the exact renormalisation group to symmetric as well as asymmetric many-fermion systems with a short-range attractive force is studied. Assuming an ansatz for the effective action with effective bosons, describing pairing effects, a set of approximate flow equations for the effective coupling including boson and fermionic fluctuations has been derived. The phase transition to a phase with broken symmetry is found at a critical value of the running scale. The mean-field results are recovered if boson-loop effects are omitted. The calculations with two different forms of the regulator are shown to lead to similar results. We find that, being quite small in the case of the symmetric many-fermion system the corrections to mean-field approximation become more important with increasing mass asymmetry.