Speaker
Description
Recent astronomical observations now tightly constrain the neutron-star EoS at intermediate densities, where matter may be neither purely hadronic nor weak-coupling quark matter. The favored “stiff” EoS can feature c_s^2 > 1/3 and even a negative (normalized) trace anomaly, challenging normal-phase NNLO pQCD predictions. Based on arXiv:2411.03781, I examine whether this tension can be accounted for by thermodynamic effects of pairing (color superconducting/superfluid) gaps, within a unified perturbative framework that treats diquark superfluidity in two-color QCD, pion condensation at large isospin density, and two-flavor color-superconducting (2SC) quark matter on the same footing.
Technically, I highlight three points: (1) for both c_s^2 and the trace anomaly, a consistent treatment must account not only for the maximal gap magnitude Δ but also for its μ-dependence (including ∂Δ/∂μ_q); (2) with this dependence included, the gap contribution tends to push the trace anomaly negative, whereas the correction to c_s^2 need not be large; and (3) for higher-order corrections in the paired phase, such as O(g μ^2 Δ^2) term, (resummed) one-loop gluonic contributions are essential for quantitative control.
