Phase Transition Phenomenology with Nonparametric Representations of the Neutron Star Equation of State

Astrophysical observations of Neutron Stars (NS) allow us to probe the properties of cold, dense nuclear matter, in particular whether there are phase transitions in the Equation of State (EoS) at high densities. Previous studies adopted ad hoc parametric models in attempt to capture particular features thought to be common to some phase transitions. However, such models can introduce strong priors on the types of behavior allowed within the EoS, and these assumptions may not be warranted. We, instead, avoid these issues by extracting features common to many phase transitions directly from the EoS without relying on an underlying parametrization. After introducing the new features, we show what current astrophysical data can say about the presence or absence of phase transitions at high densities. We also discuss prospects for measuring phase transitions in NSs with future catalogs of gravitational wave observations.