Gravitational-wave imprints of nonconvex dynamics in binary neutron star mergers

Explaining gravitational-wave (GW) observations of binary neutron star (BNS) mergers requires an understanding of matter beyond nuclear saturation density. Our current knowledge of the properties of high-density matter relies on electromagnetic and GW observations, nuclear physics experiments, and general relativistic numerical simulations. In this paper we perform numerical-relativity simulations of BNS mergers subject to nonconvex dynamics, allowing for the appearance of expansive shock waves and compressive rarefactions. Using a phenomenological nonconvex equation of state we identify observable imprints on the GW spectra of the remnant. In particular, we find that nonconvexity induces a significant shift in the quasiuniversal relation between the peak frequency of the dominant mode and the tidal deformability (of order Delta f(peak)greater than or similar to 380 Hz) with respect to that of binaries with convex (regular) dynamics. Similar shifts have been reported in the literature, attributed however to first-order phase transitions from nuclear/hadronic matter to deconfined quark matter. We argue that the ultimate origin of the frequency shifts is to be found in the presence of anomalous, nonconvex dynamics in the binary remnant.