Chemical potential dependence of two-quark condensates

By adopting the background field method, the response of the dressed quark propagator to the presence of finite chemical potential is analysed up to the second order. From this, we obtain a model-independant formula for the chemical potential dependence (up to the second order) of the in-medium two-quark condensate and show both Lorentz covariance arguments and explicit calculations that the O(mu) contribution to the in-medium two-quark condensate vanishes identically.