Kaon condensation in the color-flavor-locked phase of quark matter, the Goldstone theorem, and the 2PI Hartree approximation

TL;DR

This paper investigates kaon Bose-condensation in high-density quark matter's color-flavor-locked phase using an effective scalar field theory, employing the 2PI Hartree approximation to analyze phase structure, Goldstone theorem compliance, and medium effects.

Contribution

It introduces a detailed study of kaon condensation in the CFL phase using the 2PI Hartree approximation, including renormalization and charge neutrality effects.

Findings

Phase diagram of kaon condensation mapped out.

Goldstone theorem satisfied within approximation.

Medium-dependent quasiparticle masses determined.

Abstract

At very high densities, QCD is in the color-flavor locked phase, which is a color-superconducting phase. The diquark condensates break chiral symmetry in the same way as it is broken in vacuum QCD and gives rise to an octet of pseudo-Goldstone bosons and a superfluid mode. The lightest of these are the charged and neutral kaons. For energies below the superconducting gap, the kaons are described by an $O(2)\times O(2)$-symmetric effective scalar field theory with chemical potentials. We use this effective theory to study Bose-condensation of kaons and their properties as functions of the temperature and the chemical potentials. We use the 2-particle irreducible effective action formalism in the Hartree approximation. The renormalization of the gap equations and the effective potential is studied in detail and we show that the counterterms are independent of temperature and chemical potentials.We determine the phase diagram and the medium-dependent quasiparticle masses. It is shown that the Goldstone theorem is satisfied to a very goodapproximation. The effects of imposing electric charge neutrality is examined as well.