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In this Letter, we try to give a direct method for calculating the quark-number susceptibility (QNS) at finite chemical potential and temperature. In our approach the QNS is given by a formula which solely involves G [ μ , T ] ( p → , ω n ) (the dressed quark propagator at finite chemical potential μ and temperature T). From this the QNS at finite chemical potential and temperature is calculated in the framework of rainbow-ladder approximation of the Dyson–Schwinger approach using the meromorphic quark propagator proposed in [M.S. Bhagwat, M.A. Pichowsky, P.C. Tandy, Phys. Rev. D 67 (2003) 054019]. It is found that the QNS χ ( μ , T ) has a singularity when μ comes close to a critical value μ 0 , and the susceptibility as a function of T becomes discontinuous at some values of T when μ is near μ 0 . At high temperature the QNS approaches the ideal quark gas result, while at very small temperature ( T 40 MeV ) the susceptibility equals zero. For all values of μ we studied, the susceptibility shows a rapid increase near T = 120 – 140 MeV , which could be regarded as the signal of a crossover. |
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