The ρ Meson and the Thermal Behavior of an Effective Hadronic Coupling Constant

Vector Meson Dominance ideas together with a Finite Energy QCD sum rule allows for the determination of the qand the T dependence of the effective hadronic coupling constant gρππ in the space-like region. It turns out that gρππ(q , T ) vanishes at the critical temperature Tc, independently of q . A comparison with a previous independent QCD determination of the electromagnetic pion form factor at finite temperature supports the validity of Vector Meson Dominance at finite temperature. We find also thet the pion radius increases with T , having a divergent behavior at Tc.