Maximum latent heat of neutron star matter independent of general relativity

©2022 American Physical Society Supported by Grants No. MICINN: PID2019-108655GB-I00 and No. PID2019-106080GB-C21 (Spain); the COST action CA16214 (Multimessenger Physics and Astrophysics of Neutron Stars); Universidad Complutense de Madrid under research Group No. 910309 and the IPARCOS institute. ; We establish bounds on the maximum possible specific latent heat of cold neutron-star matter derived from hadron physics alone. Existing chiral perturbation theory computations for the equation of state, together with perturbative quantum chromodynamics (QCD), relevant at highest densities (even if they would turn out not to be physically realizable) bind the maximum latent heat which is possible in actual neutron stars. Because these are already near gravitational collapse in general relativity, no denser form of cold matter can exist: thus, the bounds are a generic physical limit. Even in scenarios that modify the theory of gravity, the existence of a family of latent-heat maxima is relevant to diagnose progress in the knowledge of the equation of state of neutron matter, by quantifying the maximum possible (presumed) phase transition that its error bands would allow. Thus, latent heat is a natural benchmark for the equation of state in cold QCD. ; Depto. de Física Teórica ; Fac. de Ciencias Físicas ; TRUE ; Unión Europea. Horizonte 2020 ; Ministerio de Ciencia e Innovación (MICINN) ; Universidad Complutense de Madrid ; pub