Eur. Phys. J. A (2007) 31: 758-760
https://doi.org/10.1140/epja/i2007-10007-5

QNP 2006

Goldstone boson counting in relativistic systems at finite density

Department of Theoretical Physics, Nuclear Physics Institute, Academy of Sciences of the Czech Republic, 250 68, Řež, Czech Republic

^* e-mail: brauner@ujf.cas.cz

Received: 8 January 2007
Accepted: 15 January 2007
Published online: 22 March 2007

Abstract

We study the effects of finite chemical potential on the pattern of symmetry breaking within the relativistic linear sigma model. In accordance with previous works we show that type-II Goldstone bosons may appear whose dispersion relation is quadratic in momentum in the long-wavelength limit. We show that their presence is tightly connected with nonzero densities of non-Abelian Noether charges, and formulate a general counting rule for the number of the Goldstone bosons. Working at tree level, we conclude with the discussion of the loop effects. Our results find an application in particular to cold dense quark matter, where a type-II Goldstone boson has been found, e.g., in the phases with kaon condensation.