Impact of Multiple Phase Transitions in Dense QCD on Compact Stars. (arXiv:2306.13884v1 [nucl-th])
<a href="http://arxiv.org/find/nucl-th/1/au:+Sedrakian_A/0/1/0/all/0/1">Armen Sedrakian</a>
This review covers several recent developments in the physics of dense QCD
with an emphasis on the impact of multiple phase transitions on astrophysical
manifestations of compact stars. It is conjectured that pair-correlated quark
matter in $beta$-equilibrium is within the same universality class as
spin-imbalanced cold atoms and the isospin asymmetrical nucleonic matter, which
then implies the emergence of phases with broken space symmetries and
tri-critical (Lifshitz) points. We construct an equation of state (EoS) which
extends the two-phase EoS of dense quark matter within the constant speed of
sound parameterization by adding a conformal fluid with a speed of sound
$c_{rm conf.}=1/sqrt{3}$ at densities $ge 10n_{rm sat}$, where $n_{rm
sat}$ is the saturation density. With this input, we construct static,
spherically symmetrical compact hybrid stars in the mass-radius diagram,
recover such features as the twins and triplets, and show that the transition
to conformal fluid leads to spiraling-in of the tracks in this diagram. Stars
on the spirals are classically unstable with respect to the radial oscillations
but can be stabilized if the conversion timescale between quark and nucleonic
phases at their interface is larger than the oscillation period. Finally, we
review the impact of a transition from high-temperature gapped to
low-temperature gapless two-flavor phase on the thermal evolution of hybrid
stars.
This review covers several recent developments in the physics of dense QCD
with an emphasis on the impact of multiple phase transitions on astrophysical
manifestations of compact stars. It is conjectured that pair-correlated quark
matter in $beta$-equilibrium is within the same universality class as
spin-imbalanced cold atoms and the isospin asymmetrical nucleonic matter, which
then implies the emergence of phases with broken space symmetries and
tri-critical (Lifshitz) points. We construct an equation of state (EoS) which
extends the two-phase EoS of dense quark matter within the constant speed of
sound parameterization by adding a conformal fluid with a speed of sound
$c_{rm conf.}=1/sqrt{3}$ at densities $ge 10n_{rm sat}$, where $n_{rm
sat}$ is the saturation density. With this input, we construct static,
spherically symmetrical compact hybrid stars in the mass-radius diagram,
recover such features as the twins and triplets, and show that the transition
to conformal fluid leads to spiraling-in of the tracks in this diagram. Stars
on the spirals are classically unstable with respect to the radial oscillations
but can be stabilized if the conversion timescale between quark and nucleonic
phases at their interface is larger than the oscillation period. Finally, we
review the impact of a transition from high-temperature gapped to
low-temperature gapless two-flavor phase on the thermal evolution of hybrid
stars.
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