Ground state of stressed two-flavor quark matter

Determine whether stressed two-flavor quark matter in neutron-star cores realizes conventional 2SC, a gapless or crystalline phase, or a phase with secondary pairing of nominally unpaired quarks, and establish whether the realized phase is a superfluid.

Background

Strange-quark mass effects, beta equilibrium, and electric and color neutrality create Fermi-surface mismatches that may destabilize ideal 2SC pairing. The resulting phase determines whether rotational vortices exist in the quark core.

References

Whether this pairing survives in realistic neutron-star matter remains an important microscopic question.

— Spin-One Secondary Pairing in Two-Flavor Color Superconductivity: Spinful Relativistic Superfluidity and Anomaly Matching  (2609.24472 - Yamamoto, 21 Sep 2026) in Discussion and outlook

It remains unclear whether the resulting state is conventional 2SC, a gapless or crystalline phase, or a phase with secondary pairing of the nominally unpaired quarks.

— Superfluidity and Vortex Dynamics in Neutron Stars  (2609.01022 - Link et al., 1 Sep 2026) in Section “Open questions and perspectives” under “Quantum vorticity in quark matter”