DR. PHILIPPE LANDRY

Determining the equation of state (EoS) of neutron-star matter is a major open problem in nuclear astrophysics. While observations of neutron stars in low-mass X-ray binaries have provided some constraints on the EoS through the mass-radius relation, the most stringent ones to date come from the binary neutron-star merger GW170817. What's more, a direct inference of the EoS was performed with GW170817 by adopting a parametric model for the EoS and using gravitational wave data to constrain the parameters. In this talk, the speaker will describe an alternative approach to the inference in which the EoS is represented as a Gaussian process conditioned with input from nuclear theory. A nonparametric representation of this kind provides greater flexibility and transparency in setting the prior distribution over viable EoSs, and allows for sophisticated model selection between different features of the nuclear microphysics. He will also discuss how quasi-universal relations between neutron-star observables can be used to combine separate low-mass X-ray binary and gravitational-wave observations, without resorting to EoS modeling, in order to produce joint constraints on tidal deformability as a proxy for the EoS.