Functional renormalization group study of the Quark-Meson model with $\omega$ meson

Understand

We study the phase diagram of two-flavor massless QCD at finite baryon density by applying the functional renormalization group (FRG) for a quark-meson model with $\sigma, \pi$, and $\omega$ mesons.

• The dynamical fluctuations of quarks, $\sigma$, and $\pi$ are included into the flow equations, while the amplitudes of $\omega$-fields are also allowed to fluctuate.
• At high temperature the effects of the $\omega$-field on the phase boundary are qualitatively similar to the mean-field calculations; the phase boundary is shifted to the higher chemical potential region.
• As the temperature is lowered, however, the transition line bends back to the lower chemical potential region, irrespective to the strength of the vector coupling.