Absence of Renormalization of the Specific Heat Coefficient of the   Interacting Fermion Systems
  Contrary to the longtime and widely conceived belief, we proved that the specific heat coefficient $\gamma$ --also called Sommerfeld coefficient -- of the interacting Fermion system is not renormalized by the wave-function renormalization factor $Z$ as far as the system remains a Fermi liquid state. 
Yunkyu Bang
cond-mat.str-el