摘要
By differentiating the inverse dressed quark propagator at finite chemical potential μ with respect to μ, the linear response of the dressed quark propagato r to the chemical potential can be obtained, From this we extract a modelindependent formula for the linear chemical potential dependence of the in-medium two-quark condensate and show by two independent methods （explicit calculation and Lorentz covariance arguments） that the first-order contribution in μ to the in-medium two-quark condensate vanishes identically. Therefore if one wants to study the in-medium two-quark condensate one should expand to at/east the second order in the chemical potential μ.
基金
The project supported in part by National Natural Science Foundation of China under Grant Nos. 10175033, 10135030, 10575050, and 10475057, and the Research Fund for the Doctoral Program of Higher Education under Grant No. 20030284009
