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arXiv · 2312.11443

Enhanced contribution of the pairing gap to the QCD equation of state at large isospin chemical potential

Yuki Fujimoto
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Abstract

I study QCD at large isospin density, which is known to be in the superfluid state with Cooper pairs carrying the same quantum number as pions. I solve the gap equation derived from the perturbation theory up to the next-to-leading order corrections. The pairing gap at large isospin chemical potential is found to be enhanced compared to the color-superconducting gap at large baryon chemical potential due to the $\sqrt{2}$ difference in the exponent arising from the stronger attraction in one-gluon exchange in the singlet channel. Then, using the gap function, I evaluate the contribution of the condensation energy of the superfluid state to the QCD equation of state. At isospin chemical potential of a few GeV, where the lattice QCD and the perturbative QCD can be both applied, the effect of the condensation energy becomes dominant even compared to the next-to-leading order corrections to the pressure in the perturbation theory. It resolves the discrepancy between the recent lattice QCD results and the perturbative QCD result.

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Yuki Fujimoto. 2023-12-18. Enhanced contribution of the pairing gap to the QCD equation of state at large isospin chemical potential. https://doi.org/10.1103/physrevd.109.054035

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