Quark formation and phenomenology in binary neutron-star mergers using V-QCD

Abstract

Using full 3+1 dimensional general-relativistic hydrodynamic simulations of equal-and unequal-mass neutron-star binaries with properties that are consistent with those inferred from the inspiral of GW170817, we perform a detailed study of the quark-formation processes that could take place after merger. We use three equations of state consistent with current pulsar observations derived from a novel finite-temperature framework based on V-QCD, a non-perturbative gauge/gravity model for Quantum Chromodynamics. In this way, we identify three different post-merger stages at which mixed baryonic and quark matter, as well as pure quark matter, are generated. A phase transition triggered collapse already < ∼ 10 ms after the merger reveals that the softest version of our equations of state is actually inconsistent with the expected second-long post-merger lifetime of GW170817. Our results underline the impact that multi-messenger observations of binary neutron-star mergers can have in constraining the equation of state of nuclear matter, especially in its most extreme regimes.

A General, Scale-independent Description of the Sound Speed in Neutron Stars

“…This model gives M TOV = 2.14 M e and Λ 1.4 = 511 and therefore conveniently satisfies the 2 M e and tidal deformability constraints. Furthermore, it has recently been verified (Tootle et al 2022) via binary neutron-star merger simulations that this EOS is not excluded by the expected 1 s long lifetime (Gill et al 2019) of the postmerger remnant of GW170817. However, although this model passes all currently known theoretical and observational constraints, it is also not able to account for the softening of the core predicted by the red curve.…”

Emergence of microphysical viscosity in binary neutron star post-merger dynamics

“…Beyond uncertainties in the cold EoS, finite-temperature effects [59][60][61], the appearance of exotic degrees of freedom or phase transitions [26,[62][63][64][65][66][67][68][69], or effects from weak interactions [70,71] could alter the post-merger dynamics and systematically bias our ability to infer dense matter properties [72]. The latter remains largely not understood as it requires additional physics in the form of weak interactions [73][74][75][76] to be specified.…”

Gravitational wave signatures of phase transition from hadronic to quark matter in isolated neutron stars and binaries

“…As discussed earlier, although PT in isolated NS is possible, PT is more likely to happen during BNSM, where the density of the merger product rises to large values. There has been quite a number of works which discusses the possible post-merger signals resulting from such PT at the core of the merger product [45][46][47][48]. The post-merger signals for PT depend strongly on the EoS of the corresponding HM and QM but also on the critical density above which the quarks start appearing in the system (also known as the onset point).…”