Quark and Gluon Condensates at Finite Temperatures by the Linear Sigma Model Approach

Based on a linear sigma model, we discuss the mixing between a quark condensate and a gluon condensate. It is shown that the linear sigma model will not be self-consistent if we switch off the mixing coupling between glueball and chiral fields. By introducing a proper mixing coupling, we realize the second-order phase transitions of chiral symmetry restoration and deconfinement. We further show that the critical temperature of chiral symmetry restoration could not be larger than the temperature of deconfinement phase transition in all possible parameter spaces of our model.