EFFECTIVE CHIRAL LAGRANGIAN FROM QCD AT NONZERO CHEMICAL-POTENTIAL

We start from the euclidean QCD action for gluons and massless quarks with N-c colours at finite baryon chemical potential ps and zero temperature. For mu(B) of the order of external momenta o(p) we derive an euclidean effective real chiral lagrangian at finite pe, up to and including o(p(4)), in terms of Goldstone Bosons (GB), in the large N-c limit, including gluon contributions. Our effective action generalizes non-trivially the one obtained for mu(B) = 0 by previous authors, and it includes new mu(B)-dependent terms. In particular, a topological term mu(B)N(B) is found, N-B being the baryon number in terms of GB fields with the correct normalization factor. Physical implications of the remaining mu(B)-dependent terms are discussed briefly.