@book{destri_sartirana_2005, 
  title={Improved Hartree--Fock resummations and spontaneous symmetry breaking}, 
  abstractNote={The standard Hartree--Fock approximation of the O(N)-invariant ϕ^4
model suffers from serious renormalization problems. In addition, when the
symmetry is spontaneously broken, another shortcoming appears in relation to
the Goldstone bosons: they fail to be massless in the intermediate states. In
this work, within the framework of out--of--equilibrium Quantum Field Theory,
we propose a class of systematic improvements of the Hartree--Fock resummation
which overcomes all the above mentioned difficulties while ensuring also exact
Renormalization--Group invariance to one loop.}, 
  author={Destri and Sartirana}, 
  year={2005}, 
  month={Sep}
  }