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Improved Hartree--Fock resummations and spontaneous symmetry breaking

Claudio Destri·Andrea Sartirana
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Abstract

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.

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Claudio Destri, Andrea Sartirana. 2005-09-05. Improved Hartree--Fock resummations and spontaneous symmetry breaking. https://doi.org/10.1103/physrevd.73.025012

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