Spontaneous symmetry breaking of non-Abelian symmetries at finite density: gapped Goldstones at the cutoff scale
Su invito dei Professori V. Greco e V. Branchina, giorno 28 giugno 2019, con inizio alle ore 11:30, presso la nuova Sala Riunioni del #DFA (1° piano, nei pressi del Refettorio e della Biblioteca), il Dr. G. F. Cuomo (EPFL, Lausanne, Switzerland; ex Allievo del #DFA e della SSC) terrà un seminario dal titolo Spontaneous symmetry breaking of non-Abelian symmetries at finite density: gapped Goldstones at the cutoff scale. Tutti gli interessati sono invitati a partecipare.
Abstract. At finite density, the spontaneous symmetry breaking of an internal non-Abelian symmetry does not only imply the exitstence of massless modes, but also of massive modes, whose gap is fixed by the algebra and is proportional to the chemical potential of the system: the gapped Goldstones. These modes appear in many different contexts in physics, ranging from condensed matter systems to QCD at finite isospin density in the chiral limit. I will review the basic reason for the existence of a gap as well as the basic properties concerning the gapped Goldstones interactions. Then I will show how to build a non-relativistic effective field theory, similar in spirit to the chiral Lagrangian, which realizes nonlinearly Poincaré and the internal symmetry. The effective theory includes both massless and gapped Goldstone modes and applies also when the strong coupling-scale of the system is set by the chemical potential, giving the gap to the massive modes.