Observing dense matter in the sky
The study of the properties of neutron stars is presently entering a golden age.
Observations of gravitational waves from binary neutron star mergers by the LIGO/VIRGO/KAGRA gravitational wave detectors give an upper bound on the radius of neutron stars. Measurements from phase-resolved x-ray emissions from pulsars by the NICER detector at the International Space Station tighten the possible range of the mass-radius relation of neutron stars. Future observations of gravitational waves and x-ray emissions have the potential to delineate in unprecedented details the properties of dense matter in the interior of neutron stars, i.e. the equation of state of neutron star matter.
The present astronomical data allows already at this stage to put severe limits on the possible appearance of a phase transition in the interior of neutron stars. These limits will be presented and outlines will be given how future measurements can probe the high density behaviour of neutron star matter.
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Goethe Universität Institut für Theoretische Physik, Frankfurt am MainJürgen Schaffner-Bielich is a Professor at the Goethe Universität, Frankfurt am Main where he had also completed his PhD in 1994. Subsequently he held research positions at the Niels Bohr Institute (94-96), LBNL (96-98), RIKEN BNL Research Center (98-01), Columbia University (01-02), and Stony Brook University (02-03). Between 2003 and 2008 he was a Lecturer at the Goethe Universität, before becoming Professor at the Ruprecht-Karls-Universität, Heidelberg in 2008. He returned to Goethe Universität in 2012 first as a Lecturer (12-16) and, since 2016, as a Professor. His research interests include compact stars (neutron stars, quark stars), (hyper)nuclear structure, hadrons in the medium, chiral effective models, and aspects of QCD for compact stars and the early universe.