2019/12/16 by Bastian B. Brandt, Francesca Cuteri, Brandt, B. B. +5 · 1 citation
Physics and Astronomy · #Quantum Chromodynamics and Particle Interactions #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.1912.07451
For large isospin asymmetries, perturbation theory predicts the QCD ground state to be a superfluid phase of u and d Cooper pairs. This phase, which is denoted as the BCS phase, is expected to be smoothly connected to the standard phase with Bose-Einstein condensation (BEC) of charged pions at μI≥ mπ/2 by an analytic crossover. A first hint for the existence of the BCS phase, which is likely characterised by the presence of both, deconfinement and charged pion condensation, is coming from the lattice observation that the deconfinement crossover smoothly penetrates into the BEC phase. To further scrutinize the existence of the BCS phase, in this proceedings article we investigate the complex spectrum of the massive Dirac operator in 2+1-flavor QCD at nonzero temperature and isospin chemical potential. The spectral density near the origin is related to the BCS gap via a generalization of the Banks-Casher relation to the case of complex Dirac eigenvalues (derived for the zero-temperature, high-density limits of QCD at nonzero isospin chemical potential).