Analytic description of SU(3) lattice thermodynamics in the whole temperature range within the mass gap approach

Abstract

A general approach how to analytically describe and understand $SU(3)$ lattice thermodynamics in the whole temperature range $[0, \infty)$ is formulated and used. It is based on the effective potential approach for composite operators properly extended to non-zero temperature and density. This makes it possible to introduce into this general formalism the mass gap, which is responsible for the large-scale dynamical structure of the QCD ground state. The mass gap dependent gluon plasma pressure adjusted by this approach to the corresponding lattice data is shown to be a continuously growing function of temperature being thus differentiable in every point of its domain. At the same time, the entropy and energy densities have finite jump discontinuities at some characteristic temperature $T_c = 266.5 \ \MeV$ with latent heat $\epsilon_{LH}= 1.41$. This is a firm evidence of the first-order phase transition in $SU(3)$ pure gluon plasma. The heat capacity has a $\delta$-type singularity (an essential discontinuity) at $T_c$, so that the velocity of sound squared becomes zero at this point. All the independent thermodynamic quantities are exponentially suppressed below $T_c$ and rather slowly approach their respective Stefan-Boltzmann limits at high temperatures. Those thermodynamic quantities which are the ratios of their independent counterparts such as conformity, conformality and the velocity of sound squared approach their Stefan-Boltzmann limits rather rapidly and demonstrate a non-trivial dependence on the temperature below $T_c$. We also calculate the trace anomaly relation (the interaction measure) and closely related to it the gluon condensate, which are especially sensitive to the non-perturbative effects. An analytical description of the dynamical structure of $SU(3)$ gluon plasma is given.