Speaker: Juergen Schaffner-Bielich
Abstract: Neutron Stars are born in core-collapse supernovae being the endpoint of stellar evolution of massive stars. Their extreme properties allow for the study of dense matter in the sky. In recent years the advancement of astrophysical observations has been so tremendous that the properties of neutron stars can be constrained nowadays to an unprecedented level. I will summarize the basic observations of neutron star masses from pulsar data, the constraints on radii from x-ray measurements, and the first detection of gravitational waves from a neutron star merger. On the other hand, I will discuss the nuclear and particle physics aspects of the equation of state of neutron star matter which is firmly limited at low and high energy densities. Chiral effective field theory puts a stringent constraint up to about saturation density for pure neutron matter. Perturbative QCD calculations narrow the equation of state at ultimately high densities. Finally, I will address the possible existence of new phases in the core of neutron stars which can be revealed from the mass-radius relation of neutron stars. I will argue that it is in principle impossible to rule out phase transitions in neutron stars from observations based on general relativity alone.
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