Chiral symmetry restoration in the massive Thirring model at finite T and mu: dimensional reduction and the Coulomb gas

We show that in certain limits the (1 + 1)-dimensional massive Thirring mod el at finite temperature T is equivalent to a one-dimensional Coulomb gas o f charged particles at the same T. This equivalence is then used to explore the phase structure of the massive Thirring model. For strong coupling and T much greater than m (the fermion mass), the system is shown to behave as a free gas of "molecules" (charge pairs in the Coulomb gas terminology) ma de of pairs of chiral condensates. This binding of chiral condensates is re sponsible for the restoration of chiral symmetry as T --> infinity, In addi tion, when a fermion chemical potential mu not equal 0 is included, the ana logy with a Coulomb gas still holds with mu playing the role of a purely im aginary external electric field. For small T and mu we find a typical massi ve Fermi gas behaviour for the fermion density, whereas for large mu it sho ws chiral restoration by means of a vanishing effective fermion mass. Some similarities with the chiral properties of low-energy QCD at finite T and b aryon chemical potential are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.