Speaker
Description
The equation of state of deconfined strongly interacting matter at high densities remains an open question, with effects from quark pairing in the preferred color-flavor-locked (CFL) ground state possibly playing an important role. Recent studies suggest that at least large pairing gaps in the CFL phase are incompatible with current astrophysical observations of neutron stars. At the same time, it has recently been shown that in two-flavor quark matter, subleading corrections from pairing effects can be much larger than would be naively expected, even for comparatively small gaps. Here, I present next-to-leading-order corrections to the pressure of quark matter in the CFL phase arising from the gap and the strong coupling constant, incorporating neutron-star equilibrium conditions and current state-of-the-art perturbative QCD results. The corrections are again quite sizable, and they allow one to constrain the CFL gap in the quark energy spectrum to $\Delta_\mathrm{CFL} \lesssim 140\,\mathrm{MeV}$ at a baryon chemical potential $\mu_\mathrm{B} = 2.6\,\mathrm{GeV}$, even when allowing for a wide range of possible behaviors for the dependence of the gap on the chemical potential.