Structural glass transition and the entropy of the metastable states

The metastable states of a glass are localized and counted by adding a weak pinning field that explicitly breaks the ergodicity. The entropy of the metastable states, that is, the logarithm of their number, is extensive in a range of temperatures Ts<T<Tc only. It is argued that Ts and Tc are the ideal calorimetric and kinetic transition temperatures, respectively. An explicit computation of the metastable states entropy for a (2)2 model is given.