We present the first calculation of the fermion spectral function at finite temperature in the quark-meson model in the framework of the functional renormalization group. We compare the results in two truncations; after first evolving the flow equation of effective potential, we investigate the spectral function either by taking the IR values as input to calculate one-loop self-energy or by taking the scale-dependent values as input to evolve the flow equation of the fermion two-point function. The latter one is a self-consistent procedure in the framework of the functional renormalization group. In both truncations, we find a multipeak structure in the spectral function, indicating quark collective excitations realized in terms of the Landau damping. However, in contrast to the fermion zero mode in the one-loop truncation, we find a fermion soft mode in the self-consistent truncation, which approaches the zero mode as the temperature increases.

• Received 9 October 2018

DOI:https://doi.org/10.1103/PhysRevD.98.094031

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Published by the American Physical Society