Colloquium - Yeunhwan Lim

Dr. Yeunhwan Lim

Adjunct Professor
Dept. of Mathematics & Statistics, University of Guelph Guelph, Canada

Neutron Stars and Nuclear Equation of States

Neutron stars have been among the most important objects in both nuclear physics and astrophysics since their existence was proposed in the 1930s and pulsars were first discovered in 1967. Recent advances in multimessenger observations have provided increasingly stringent constraints on neutron-star properties. In particular, measurements from the Neutron Star Interior Composition Explorer (NICER) and gravitational-wave observations by ground-based detectors such as LIGO have significantly improved our knowledge of the masses and radii of neutron stars.

In this talk, I will discuss how neutron stars can be studied from the perspective of nuclear physics, with particular emphasis on the nuclear equation of state (EOS) over a wide range of densities. I will review several approaches to describing dense nuclear matter, including conventional phenomenological nuclear models, ab initio many-body calculations, and more general descriptions based on the speed of sound.

I will then discuss how the nuclear EOS can be constrained by combining information from nuclear theory, laboratory experiments, and astrophysical observations. These complementary constraints probe different density regions and therefore provide a powerful way to reduce the uncertainty in the EOS of neutron-rich matter.

Finally, I will demonstrate how the predicted probability distributions of neutron-star masses and radii are modified as different nuclear-physics and astrophysical constraints are progressively incorporated, and discuss what these combined constraints can tell us about the properties of dense matter inside neutron stars.