Stiffening of matter in quark-hadron continuity. (arXiv:2106.06687v2 [nucl-th] UPDATED)
<a href="http://arxiv.org/find/nucl-th/1/au:+Kojo_T/0/1/0/all/0/1">Toru Kojo</a>
We discuss stiffening of matter in quark-hadron continuity. We introduce a
model that relates quark wavefunctions in a baryon and the occupation
probability of states for baryons and quarks in dense matter. In dilute regime,
the confined quarks contribute to the energy density through the masses of
baryons, but do not directly contribute to the pressure, hence the equations of
state are very soft. This dilute regime continues until the low momentum states
for quarks get saturated; this may happen even before baryons fully overlap,
possibly at density slightly above the nuclear saturation density. After the
saturation the pressure grows rapidly while changes in energy density are
modest, producing a peak in the speed of sound. If we use baryonic descriptions
for quark distributions near the Fermi surface, we reach a description similar
to the quarkyonic matter model of McLerran and Reddy. With a simple adjustment
of quark interactions to get the nucleon mass, our model becomes consistent
with the constraints from 1.4-solar mass neutron stars, but the high density
part is too soft to account for two-solar mass neutron stars. We delineate the
relation between the saturation effects and short range interactions of quarks,
suggesting interactions that leave low density equations of state unchanged but
stiffen the high density part.
We discuss stiffening of matter in quark-hadron continuity. We introduce a
model that relates quark wavefunctions in a baryon and the occupation
probability of states for baryons and quarks in dense matter. In dilute regime,
the confined quarks contribute to the energy density through the masses of
baryons, but do not directly contribute to the pressure, hence the equations of
state are very soft. This dilute regime continues until the low momentum states
for quarks get saturated; this may happen even before baryons fully overlap,
possibly at density slightly above the nuclear saturation density. After the
saturation the pressure grows rapidly while changes in energy density are
modest, producing a peak in the speed of sound. If we use baryonic descriptions
for quark distributions near the Fermi surface, we reach a description similar
to the quarkyonic matter model of McLerran and Reddy. With a simple adjustment
of quark interactions to get the nucleon mass, our model becomes consistent
with the constraints from 1.4-solar mass neutron stars, but the high density
part is too soft to account for two-solar mass neutron stars. We delineate the
relation between the saturation effects and short range interactions of quarks,
suggesting interactions that leave low density equations of state unchanged but
stiffen the high density part.
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