Incorporating pQCD calculations into neutron star equation of state inference

Although perturbative quantum chromodynamics (pQCD) is valid only at densities exceeding those found in the cores of neutron stars, it is now known to provide valuable insights into the neutron star equation of state (EOS). In this work, we explore methods for incorporating pQCD information into neutron star EOS inference using a nonparametric model based on Gaussian processes (GPs). Following previous work, we first examine the impact of pQCD constraints using a "pQCD likelihood" method. While this method can be easily integrated into existing EOS inference frameworks, it requires an arbitrary choice of density at which to apply the constraints. To address this limitation we extend the GP model to higher densities, providing a unified description of the EOS across the entire density range from neutron star to pQCD densities. In this approach the pQCD constraints effectively become part of the prior, thereby incorporating them more naturally. We compare our method with the traditional likelihood-based application of pQCD constraints and offer insights that could improve EOS inference for neutron stars.