Phase Structure of Four-Fermion Theories at Finite Temperature and Chemical Potential in Arbitrary Dimensions

Abstract

The phase structure of four-fermion theories is thoroughly investigated with varying temperature and chemical potential for arbitrary space-time dimensions $(2\le D<4)$ by using the 1/N expansion method. It is shown that the chiral symmetry is restored in the theory under consideration for sufficiently high temperature and/or chemical potential. The critical line dividing the symmetric and broken phase is given explicitly. It is found that for space-time dimension $2\le D<3$ both the first-order and second-order phase transition occur depending on the value of temperature and chemical potential while for $3\le D<4$ only the second-order phase transition exists.

Comments: 32 pages, uses LaTeX, here.sty(attached), eepic.sty, HUPD-9402 (some misprints corrected)