FRG analysis for a relativistic BEC in arbitrary spatial dimensions

Abstract A relativistic Bose–Einstein condensate (BEC) is studied within the complex scalar field theory using the functional renormalization group (FRG) under the local potential approximation. We investigate fluctuation effects on the relativistic BEC through numerical analyses for various spatial dimensions and chemical potentials. Our numerical results are consistent with the Mermin–Wagner theorem, and this consistency is also analytically confirmed from the flow equation. We also discuss a numerical instability of the FRG in lower spatial dimensions, which is avoidable for certain parameter choices.