Tidal Deformability Doppelgangers: Implications of a low-density phase transition in the neutron star equation of state

Understand

Studying the properties of ultra-dense matter is one of the key goals of modern neutron star research.

• The measurement of the tidal deformability from the inspiral of a binary neutron star merger offers one promising method for constraining the equation of state (EoS) of cold, dense matter.
• In this work, we report on a new class of EoSs which have significantly different pressures at nuclear densities and large differences in stellar radii, but that predict surprisingly similar tidal deformabilities across the entire range of astrophysically-observed neutron star masses.
• Using a survey of 5 million piecewise polytropic EoSs, subject to five different sets of nuclear priors, we demonstrate that these "tidal deformability doppelgangers" occur generically.