81 research outputs found
Neutron stars as probes of extreme energy density matter
Neutron stars have long been regarded as extra-terrestrial laboratories from
which we can learn about extreme energy density matter at low temperatures. In
this article, I highlight some of the recent advances made in astrophysical
observations and related theory. Although the focus is on the much needed
information on masses and radii of several individual neutron stars, the need
for additional knowledge about the many facets of neutron stars is stressed.
The extent to which quark matter can be present in neutron stars is summarized
with emphasis on the requirement of non-perturbative treatments. Some
longstanding and new questions, answers to which will advance our current
status of knowledge, are posed.Comment: 18 pages, 3 figures, 3 tables, Review submitted to Praman
Generic conditions for stable hybrid stars
We study the mass-radius curve of hybrid stars, assuming a single first-order
phase transition between nuclear and quark matter, with a sharp interface
between the quark matter core and nuclear matter mantle. We use a generic
parameterization of the quark matter equation of state, which has a constant,
i.e. density-independent, speed of sound ("CSS"). We argue that this
parameterization provides a framework for comparison and empirical testing of
models of quark matter. We obtain the phase diagram of possible forms of the
hybrid star mass-radius relation, where the control parameters are the
transition pressure, energy density discontinuity, and the quark matter speed
of sound. We find that this diagram is sensitive to the quark matter parameters
but fairly insensitive to details of the nuclear matter equation of state.
We calculate the maximum hybrid star mass as a function of the parameters of
the quark matter EoS, and find that there are reasonable values of those
parameters that give rise to hybrid stars with mass above .Comment: 11 pages, 8 figures. Changes to nomenclature, references adde
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