Time & Place: Sep. 26 (Wednesday), 2:30pm, Room 9409

Title: From hadrons to quarks in neutron stars

Speaker: Prof. Toru Kojo
Title: From hadrons to quarks in neutron stars

Abstract:
Neutron stars are cosmic laboratories to study the properties of dense
QCD matter at almost zero temperature. The neutron star mass-radius
relation has the one-to-one correspondence to the QCD equation of state
and gives strong constraints on our understanding on the properties of
the matter. I review recent developments in neutron star observations
and combine them together with the constraints from nuclear laboratory
experiments as well as low- and high-density limits of QCD calculations.
I will argue that what the current constraints tell about the QCD phase
structure and effective degrees of freedom in cold matter. I will
discuss that many neutron stars are in the domain beyond purely hadronic
regime so that the understanding based on quark degrees of freedom will
be essential. It will be argued that the easiest way to be compatible
with the existing constraints is to assume the crossover transition from
hadronic to quark matter and to describe quark matter based on the
picture used in the hadron spectroscopy. The guide line to improve the
quark matter description in practice will be also discussed.