We discuss the glueball contribution to the equation of state (EoS) of hot gluon matter below and above $T_c$. It is shown that the strong changing of masses of scalar and pseudoscalar glueballs near $T_c$ plays very important role in the thermodynamics of $SU(3)$ gauge theory. In particular, we give the arguments that these glueballs become massless at $T_G\approx 1.1T_c$ and this phenomenon is crucial in understanding of the mystery in the behavior of trace anomaly founded in the lattice calculation.
Categories: hep-ph hep-ex nucl-ex nucl-th