Temperature dependence of nuclear spin-isospin response and beta decay in hot astrophysical environments

TL;DR

This paper develops a microscopic finite-temperature relativistic nuclear response model to study how temperature affects spin-isospin excitations and beta decay rates in nuclei relevant to astrophysics.

Contribution

It introduces a novel finite-temperature formalism for relativistic nuclear field theory that includes phonon couplings without free parameters, extending beyond the random phase approximation.

Findings

Beta decay rates are highly sensitive to low-energy spin-isospin strength at finite temperature.

Temperature significantly influences Gamow-Teller and spin dipole resonances in selected nuclei.

Enhanced low-energy transitions impact beta decay lifetimes in hot astrophysical environments.

Abstract

A microscopic approach to the proton-neutron nuclear response is formulated in the finite-temperature relativistic nuclear field theory framework. The approach is based on the meson-nucleon Lagrangian of quantum hadrodynamics and advances the relativistic field theory for spin-isospin response beyond the finite-temperature random phase approximation. The dynamical contribution to the in-medium proton-neutron interaction amplitude is described in a parameter-free way by the coupling between the single nucleons and strongly-correlated particle-hole excitations (phonons) within the newly developed finite-temperature formalism. In this framework we investigate temperature dependence of the Gamow-Teller and spin dipole resonances in the closed-shell nuclei $^{48}$Ca, $^{78}$Ni, and $^{132}$Sn. Broader impacts of their temperature dependence are illustrated for the associated beta decay rates and lifetimes of $^{78}$Ni and $^{132}$Sn in hot astrophysical environments. We found a remarkable sensitivity of the beta decay rates to the enhanced low-energy spin-isospin strength at finite temperature, in particular, to the contribution of the first-forbidden transitions.