PUB - Publikationen an der Universität Bielefeld

We determine the volume and mass dependence of scalar and pseudoscalartwo-point functions in N_f-flavour QCD, in the presence of an isospin chemicalpotential and at fixed gauge-field topology. We obtain these results at secondorder in the \epsilon-expansion of Chiral Perturbation Theory and evaluate allrelevant zero-mode group integrals analytically. The virtue of working with anon-vanishing chemical potential is that it provides the correlation functionswith a dependence on both the chiral condensate, \Sigma, and the pion decayconstant, F, already at leading order. Our results may therefore be useful forimproving the determination of these constants from lattice QCD calculations.As a side product, we rectify an earlier calculation of the O(\epsilon^2)finite-volume correction to the decay constant appearing in the partitionfunction. We also compute a generalised partition function which is useful forevaluating U(N_f) group integrals.