Electromagnetic response of dense quark matter around color-superconducting phase transition and QCD critical point

TL;DR

This paper investigates how electromagnetic properties like conductivity change near the QCD critical point and color-superconducting transition, revealing anomalous enhancements that could be observed in heavy-ion collisions.

Contribution

It introduces a formalism combining soft mode analysis and photon self-energy to study electromagnetic responses near QCD phase transitions.

Findings

Transport coefficients show anomalous enhancements near critical points.

Different critical exponents characterize the two phase transitions.

Potential experimental signatures in heavy-ion collisions are discussed.

Abstract

We explore how the electric conductivity and associated relaxation time are modified near the QCD critical point and the phase transition to a color superconducting phase using the two-flavor Nambu-Jona-Lasinio model with finite current quark masses. We give a comprehensive account of the nature of the soft modes associated with these phase transitions and how they affect the photon self-energy when the system approaches these phase transitions in a combined way with an emphasis on the common and different aspects in the two transitions. The formalism developed for describing the paraconductivity in metallic superconductors is used for the analysis of the photon self-energy. We show that the transport coefficients calculated from the self-energy show anomalous enhancements in both cases with different critical exponents for the individual transitions. We briefly discuss the possibility of detecting the enhancements in the relativistic heavy-ion collisions in the present and future facilities.