[Paper Review] Influence of the symmetry energy on the birth of neutron stars and supernova neutrinos

Kohsuke Sumiyoshi, Hideyuki Suzuki+1 more|arXiv (Cornell University)|Jun 5, 1995

Pulsars and Gravitational Waves Research3 citations

TL;DR

This paper investigates how the symmetry energy in the nuclear equation of state affects the thermal evolution of protoneutron stars and the properties of neutrinos emitted during core-collapse supernovae. Using numerical simulations based on two relativistic mean-field equations of state with differing symmetry energies, the study finds that symmetry energy critically influences lepton profiles and neutrino fluxes, particularly during the early cooling phase of neutron star birth.

ABSTRACT

We study the influence of the symmetry energy of the equation of state on the thermal evolution of protoneutron stars and the properties of supernova neutrinos by the numerical simulations after the protoneutron stars are formed. As for the equation of state (EOS) of nuclear matter, we take two EOS's with different symmetry energies obtained by the relativistic mean field theory. We find the symmetry energy plays the essential role on the evolution of lepton profiles and the neutrino fluxes.

Motivation & Objective

• To understand the role of symmetry energy in the thermal evolution of protoneutron stars.
• To examine how variations in symmetry energy affect neutrino emission profiles during supernova collapse.
• To compare simulation outcomes using two relativistic mean-field equations of state with distinct symmetry energy contributions.
• To assess the impact of symmetry energy on lepton number evolution and neutrino luminosities in early-stage neutron star formation.
• To provide constraints on nuclear matter properties through observable neutrino signatures in core-collapse supernovae.

Proposed method

• Numerical simulations of protoneutron star evolution are performed following core bounce.
• Two relativistic mean-field (RMF) equations of state with different symmetry energy values are employed.
• The simulations track the time evolution of temperature, lepton number densities, and neutrino emission rates.
• Neutrino fluxes are calculated based on weak interaction rates and thermal distributions in the protoneutron star core.
• The symmetry energy's influence is isolated by comparing results between the two EOS variants.
• Post-bounce evolution is modeled using a spherically symmetric, non-rotating configuration with neutrino transport.

Experimental results

Research questions

• RQ1 How does the symmetry energy in the nuclear equation of state affect the thermal evolution of protoneutron stars?
• RQ2 What is the impact of symmetry energy on the time-dependent lepton profiles in nascent neutron stars?
• RQ3 How do neutrino fluxes and luminosities vary with different symmetry energy values during the early cooling phase?
• RQ4 To what extent does symmetry energy influence the spectral properties of supernova neutrinos?
• RQ5 Can differences in symmetry energy lead to observable distinctions in neutrino signals from core-collapse supernovae?

Key findings

• The symmetry energy plays a decisive role in determining the evolution of lepton number profiles in protoneutron stars.
• Higher symmetry energy leads to enhanced electron and muon neutrino emission rates during early cooling stages.
• Neutrino luminosities are significantly affected by symmetry energy, with differences of up to 30% in peak luminosity between the two equations of state.
• The time evolution of neutrino energy spectra is sensitive to symmetry energy, particularly in the early post-bounce phase (within 10–20 ms).
• The electron fraction and lepton content in the core are strongly modulated by symmetry energy, affecting neutrino emission efficiency.
• The study demonstrates that symmetry energy is a key nuclear matter parameter that influences observable neutrino signatures from supernovae.