Finite Size Effect on the in-Medium Chiral Condensate at Finite Density

The in-medium quark condensate is studied with an equivalent quark mass approach that has the advantage of no need for extra assumptions on the current mass derivatives of model parameters with respect to the quark current mass. It is found that the ratio of the quark condensate in a medium to that in a vacuum depends not only on density but also on the finite size. With decreasing volume, it decreases to a minimum, and then saturates at a radius of about 1 fm. The condensate approaches to its bulk value when the volume becomes infinitely large, and it decreases linearly with increasing density if the density is extremely low.