Sound velocity in dense stellar matter with strangeness and compact stars. (arXiv:1906.00826v3 [nucl-th] UPDATED)
<a href="http://arxiv.org/find/nucl-th/1/au:+Xia_C/0/1/0/all/0/1">Chengjun Xia</a>, <a href="http://arxiv.org/find/nucl-th/1/au:+Zhu_Z/0/1/0/all/0/1">Zhenyu Zhu</a>, <a href="http://arxiv.org/find/nucl-th/1/au:+Zhou_X/0/1/0/all/0/1">Xia Zhou</a>, <a href="http://arxiv.org/find/nucl-th/1/au:+Li_A/0/1/0/all/0/1">Ang Li</a>
The phase state of dense matter in the intermediate density range ($sim$1-10
times the nuclear saturation density) is both intriguing and unclear and could
have important observable effects in the present gravitational wave era of
neutron stars. As the matter density increases in compact stars, the sound
velocity is expected to approach the conformal limit ($c_s/c=1/sqrt{3}$) at
high densities and should also fulfill the causality limit ($c_s/c<1$).
However, its detailed behavior remains a hot topic of debate. It was suggested
that the sound velocity of dense matter could be an important indicator for a
deconfinement phase transition, where a particular shape might be expected for
its density dependence. In this work, we explore the general properties of the
sound velocity and the adiabatic index of dense matter in hybrid stars, as well
as in neutron stars and quark stars. Various conditions are employed for
hadron-quark phase transition with varying interface tension. We find that the
expected behavior of the sound velocity can also be achieved by the
nonperturbative properties of the quark phase, in addition to a deconfinement
phase transition. And it leads to a more compact star with a similar mass. We
then propose a new class of quark star equation of states, which could be
tested by future high-precision radius measurements of pulsar-like objects.
The phase state of dense matter in the intermediate density range ($sim$1-10
times the nuclear saturation density) is both intriguing and unclear and could
have important observable effects in the present gravitational wave era of
neutron stars. As the matter density increases in compact stars, the sound
velocity is expected to approach the conformal limit ($c_s/c=1/sqrt{3}$) at
high densities and should also fulfill the causality limit ($c_s/c<1$).
However, its detailed behavior remains a hot topic of debate. It was suggested
that the sound velocity of dense matter could be an important indicator for a
deconfinement phase transition, where a particular shape might be expected for
its density dependence. In this work, we explore the general properties of the
sound velocity and the adiabatic index of dense matter in hybrid stars, as well
as in neutron stars and quark stars. Various conditions are employed for
hadron-quark phase transition with varying interface tension. We find that the
expected behavior of the sound velocity can also be achieved by the
nonperturbative properties of the quark phase, in addition to a deconfinement
phase transition. And it leads to a more compact star with a similar mass. We
then propose a new class of quark star equation of states, which could be
tested by future high-precision radius measurements of pulsar-like objects.
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