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Abstract:
First-order phase transitions in many-fermion systems are not detected
in the susceptibility analysis of common renormalization-group (RG)
approaches. Here, we introduce a counterterm technique within the
functional renormalization-group (fRG) formalism which allows access to
all stable and metastable configurations. It becomes possible to study
symmetry-broken states which occur through first-order transitions as
well as hysteresis phenomena. For continuous transitions, the standard
results are reproduced. As an example, we study discrete-symmetry
breaking in a mean-field model for a commensurate charge-density wave.
An additional benefit of the approach is that away from the critical
temperature for the breaking of discrete symmetries large interactions
can be avoided at all RG scales.
