Ultra-soft fermionic excitation at finite chemical potential

Jean-Paul Blaizot (1) , Daisuke Satow (2, 3)

1 IPHT - Institut de Physique Théorique - UMR CNRS 3681
2 RIKEN RNC - Theoretical Research Division [RIKEN, Japon]
3 BNL - Brookhaven National Laboratory [Upton, NY]

It has been suggested previously that an ultra-soft fermionic excitation develops, albeit with a small spectral weight, in a system of massless fermions and scalar bosons with Yukawa interaction at high temperature ($T$). In this paper we study how this excitation is modified at finite chemical potential ($\mu$). We relate the existence of the ultra-soft mode to symmetries, in particular charge conjugation, and a supersymmetry of the free system which is spontaneously broken by finite temperature and finite density effects, as argued earlier by Lebedev and Smilga. A non vanishing chemical potential breaks both symmetries explicitly, and maximally at zero temperature where the mode ceases to exist. A detailed calculation indicates that the ultra-soft excitation persists as long as $T\geq$0.71$\mu$.

Domains: High Energy Physics - Phenomenology [hep-ph]

Jean-Paul Blaizot, Daisuke Satow. Ultra-soft fermionic excitation at finite chemical potential. Physical Review D, 2014, 89, pp.096001. ⟨10.1103/PhysRevD.89.096001⟩. ⟨cea-00979552⟩