Fluctuations and phases in baryonic matter

The phase structure of baryonic matter is investigated with focus on the role of fluctuations beyond the mean-field approximation. The prototype test case studied is the chiral nucleon-meson model, with added comments on the chiral quark-meson model. Applications to the liquid-gas phase transition in nuclear matter and extensions to dense matter are performed. The role of vacuum fluctuations and thermal excitations is systematically explored. It is pointed out that such fluctuations tend to stabilise the hadronic phase characterised by spontaneously broken chiral symmetry, shifting the chiral restoration transition to very high densities. This stabilisation effect is shown to be further enhanced by additional dynamical fluctuations treated with functional renormalisation group methods.

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