Equation of state for SU(3) gauge theory via the energy-momentum tensor under gradient flow

The energy density and the pressure of SU(3) gauge theory at finite temperature are studied by direct lattice measurements of the renormalized energy-momentum tensor obtained by the gradient flow. Numerical analyses are carried out with β=6.287–7.500 corresponding to the lattice spacing a=0.013–0.061 fm. The spatial (temporal) sizes are chosen to be Ns=64, 96, 128 (Nτ=12, 16, 20, 22, 24) with the aspect ratio, 5.33≤Ns/Nτ≤8. Double extrapolation, a→0 (the continuum limit) followed by t→0 (the zero flow-time limit), is taken using the numerical data. Above the critical temperature, the thermodynamic quantities are obtained with a few percent precision including statistical and systematic errors. The results are in good agreement with previous high-precision data obtained by using the integral method.