Damping of giant dipole resonances at finite temperature

The damping width γ^↓_GDR of the giant dipole resonance, due to its coupling to doorway states, is studied within the framework of the thermal Green's functions theory. It is found that γ^↓_GDR reflects the temperature dependence of the single-particle damping width but, as a consequence of the cancellation effects between self-energy and vertex contributions, the coefficient of such a dependence is so small that it can essentially be neglected, within the temperature range of physical interest.