Vector-axial-vector mixing from a chiral effective field theory at finite temperature

We study the vector-axial-vector mixing in a hot medium and its evolution toward the chiral phase transition using different symmetry restoration scenarios based on the generalized hidden local symmetry framework. We show that the presence of the a1 meson reduces the vector spectral function around the ρ meson mass and enhances it around the a1 meson mass. The coupling strength of a1 to ρ and π vanishes at the critical temperature due to the degenerate ρ-a1 masses. This feature holds rigorously in the chiral limit and still stays intact to good approximation for the physical pion mass.