nEoS: neutron star equation of state from hadron physics alone

Abstract

We contribute a publicly available set of tables and code to provide Equations of State (EoS) for matter at neutron star densities. Our EoSes are constrained only by input from hadron physics and fundamental principles, without feedback from neutron star observations, and so without relying on General Relativity. They can therefore be used to test General Relativity itself, as well as modified gravity theories, with neutron star observables, without logical circularity. We have adapted state of the art results from N N chiral potentials for the low-density limit, pQCD results for the asymptotically high-density EoS, and use monotonicity and causality as the only restrictions for intermediate densities, for the EoS sets to remain as modelindependent as is feasible today.

Hadron matter in neutron stars in view of gravitational wave observations

“…Thus, testing theories of gravity requires feedback from hadron physics that is free of circular reasoning and where no astrophysical input related in any way to GR has been assumed 2 . We have setup a website providing hadron physics EoS that use the best available information in the literature from earthly laboratories and theory alone [28], in http://teorica.fis.ucm.es/nEoS/ .…”

“…The top right plot in the figure shows three calculations of M (R) with various equations of state from [28] and [46] (the details are unimportant now). The true curve M (R) is one of the traditional major goals of investigation in the field.…”

“…(26) shows that the gravitational wave signal is sensitive to the tidal deformability Λ, defined as the coefficient of proportionality, of both stars, though in the combination of Eq. (28). Even before the contact between the two inspiralling neutron stars, the tides excited due to their finite size detract energy from the orbit, so that the inspiral takes less time.…”

“…in terms of the joint Λ defined in Eq. (28). The correction to 6th postNewtonian order is known [8] and only needed if Λ could be measured to percent precision.…”

“…Therefore, we have developed a set of EoS recently reported in [28] to sample EoS at intermediate densities. We sample the uncertainty bands of Chiral Perturbation Theory (at low density), the band of perturbative QCD (at high density) and interpolate between both of them at intermediate density.…”