Ultra-soft fermionic excitation at finite chemical potential

Abstract

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 $T\gtrsim \mu$.

10 pages, 8 figures. v2: Figs. 7 and 8 are added, detailed discussion on value of chemical potential in which the ultrasoft mode persists are added in Sec. III-C

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• Goldstino in supersymmetric Bose-Fermi mixtures in the presence of Bose Einstein condensate
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• Recent progress in hard-thermal-loop QCD thermodynamics and collective excitations
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• Universality of Hard-Loop Action
• Supersymmetric plasma systems and their nonsupersymmetric counterparts
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