Covariant variational approach to Yang-Mills theory at finite temperatures

We extend the covariant variational approach for $SU(N)$ Yang-Mills theory in Landau gauge to nonzero temperatures. The renormalization of the zero-temperature case is revisited and it is shown that the same counterterms are sufficient to render the low-order Green's function finite at nonzero temperature. We compute the ghost and gluon propagator numerically and show that it agrees in all qualitative respects with the results of high-precision lattice calculations.