Influence of finite chemical potential on the fermion chiral condensate in QED3

In this Letter, we generalize our previous work [H.T. Feng, F.Y. Hou, X. He, W.M. Sun, H.S. Zong, Phys. Rev. D 73 (2006) 016004] on the effect of finite chemical potential mu on the fermion propagator in QED(3) from the rainbow approximation (bare vertex approximation) of the Dyson-Schwinger approach to the case of an improved fermion-photon vertex ansatz. We show that, for this choice of the fermion-photon vertex the fermion propagator at finite chemical potential can still be written as (S) over cap (-1)(mu, p) = i gamma center dot (p) over tildeA((p) over tilde (2)) + B((p) over tilde (2)), where (p) over tilde = ((p) over right arrow, p(3) + i mu) and S-1 (p) = i gamma center dot pA(p(2)) + B(p(2)) is the fermion propagator at mu = 0. By application of this result, the fermion chiral condensate is evaluated for the range N is an element of [0, 3.0] (N denotes the number of fermion flavors) and mu is an element of [0, 10(-2)] and the influence of small chemical potential on the critical number of fermion flavors N-c is analyzed. A comparison with the rainbow approximation results is made. (c) 2008 Elsevier B.V. All rights reserved.