  The hadronic mechanism which leads to chiral symmetry restoration is explored
in the context of the rho-pi-a_1 system using Massive Yang-Mills, a hadronic
effective theory which governs their microscopic interactions. In this
approach, vector and axial-vector mesons are implemented as gauge bosons of a
local chiral gauge group. We have previously shown that this model can describe
the experimentally measured vector and axial-vector spectral functions in
vacuum. Here, we carry the analysis to finite temperatures by evaluating medium
effects in a pion gas and calculating thermal spectral functions. We find that
the spectral peaks in both channels broaden along with a noticeable downward
mass shift in the a_1 spectral peak and negligible movement of the rho peak.
The approach toward spectral function degeneracy is accompanied by a reduction
of chiral order parameters, i.e., the pion decay constant and scalar
condensate. Our findings suggest a mechanism where the chiral mass splitting
induced in vacuum is burned off. We explore this mechanism and identify future
investigations which can further test it.
