  We investigate the breakdown of supersymmetry at finite temperature. While it
has been proven that temperature always breaks supersymmetry, the nature of
this breaking is less clear. On the one hand, a study of the Ward-Takahashi
identities suggests a spontaneous breakdown of supersymmetry without the
existence of a Goldstino, while on the other hand it has been shown that in any
supersymmetric plasma there should exist a massless fermionic collective
excitation, the phonino. Aim of this work is to unify these two approaches. For
the Wess-Zumino model, it is shown that the phonino exists and contributes to
the supersymmetric Ward-Takahashi identities in the right way displaying that
supersymmetry is broken spontaneously with the phonino as the Goldstone
fermion.
