# The Modern Physics of Compact Stars and Relativistic Gravity 2021

Sep 27 – 30, 2021
Yerevan, Armenia
Etc/GMT+4 timezone

## High-density nuclear symmetry energy from neutron star observations

Sep 27, 2021, 7:00 PM
45m
Yerevan, Armenia

#### Yerevan, Armenia

Department of Physics, Alex Manukyan str. 1, Yerevan, Armenia

Bao-An Li

### Description

The density dependence of nuclear symmetry energy is among the most uncertain parts of the Equation of State (EOS) of dense neutron-rich nuclear matter. It is currently poorly known especially at suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. Because of its broad impacts on many interesting issues, to pin down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. New observational data of neutron stars including their masses, radii, and tidal deformations since GW170817 have helped improve our knowledge about nuclear symmetry energy especially at high densities. In this talk, after reviewing existing constraints on characteristics of nuclear symmetry energy around the saturation density of nuclear matter from terrestrial nuclear experiments and observations of canonical neutron stars, we discuss how the lower radius boundary $R_{2.01}=12.2$ km from NICER's very recent observation of PSR J0740+6620 of mass $2.08\pm 0.07$ $M_{\odot}$ and radius $R=12.2-16.3$ km at 68\% confidence level sets a tight lower limit for nuclear symmetry energy at densities above twice the saturation density of nuclear matter.