UA(1)symmetry restoration at high baryon density

We study the relation between chiral and UA(1)symmetries in the quark-meson model.Although quarks and mesons are described in mean field approximation,the topological susceptibility characterizing the UA(1)breaking comprises two components:one controlled by the condensate and the other by the meson fluctuation.The UA(1)restoration is governed by the competition of these components.In a hot medium,the condensates melt.However,the fluctuation is enhanced.Therefore,the UA(1)symmetry cannot be solely restored via the temperature effect.Nevertheless,the baryon density reduces the condensates and fluctuation,and thereby,the UA(1)symmetry can only be restored in a dense or dense and hot medium.The strange condensate plays a weak role in the susceptibility,and the chiral and UA(1)symmetry restorations occur almost at the same critical point.