81 research outputs found
Phenomenological QCD equations of state for neutron star mergers
Thermal QCD equations of state at high baryon density are sensitive to the
phase structure and the resulting excitation modes. The leading contribution at
low temperature can be either ~p_F^2 T^2 (pF: Fermi momentum, T: temperature)
for phases with gapless quarks, or ~T^4 for phases with gapped quarks. In the
latter the thermal pressure is dominated by collective modes. Starting with a
schematic quark model developed for neutron star structure, we estimate the
thermal contributions and zero point energy from the Nambu-Goldstone modes by
building them upon the mean field background for the color-flavor-locked quark
matter. Applying the phase shift representation for thermodynamic potentials,
we include not only the bound state pairs but also resonating pairs. According
to the Levinson's theorem, the high energy contributions tend to cancel the
pole contributions to the thermodynamics, tempering the UV behaviors in the
zero point energy. Our primary target in this talk is the domain with baryon
density nB as large as ~ 5-10n_0 (n_0 = 0.16 fm^{-3}: nuclear saturation
density), and the temperature T of the order ~30-100 MeV. The insights into
this domain may be obtained through the future detection of gravitational waves
from neutron star merging events.Comment: 5 pages, 2 figures; prepared for quark matter 2017, Chicago,
Illinois, US
Phenomenological neutron star equations of state: 3-window modeling of QCD matter
We discuss the 3-window modeling of cold, dense QCD matter equations of state
at density relevant to neutron star properties. At low baryon density, n_B < ~
2n_s (n_s: nuclear saturation density), we utilize purely hadronic equations of
state that are constrained by empirical observations at density n_B ~ n_s and
neutron star radii. At high density, n_B > ~ 5n_s, we use the percolated quark
matter equations of state which must be very stiff to pass the two-solar mass
constraints. The intermediate domain at 2 < n_B/n_s < 5 is described as neither
purely hadronic nor percolated quark matter, and the equations of state are
inferred by interpolating hadronic and percolated quark matter equations of
state. Possible forms of the interpolation are severely restricted by the
condition on the (square of) speed of sound, 0 < c_s^2 < 1. The characteristics
of the 3-window equation of state are compared with those of conventional
hybrid and self-bound quark matters. Using a schematic quark model for the
percolated domain, it is argued that the two-solar mass constraint requires the
model parameters to be as large as their vacuum values, indicating that the
gluon dynamics remains strongly non-perturbative to n_B ~ 10n_s. The hyperon
puzzle is also briefly discussed in light of quark descriptions.Comment: 18 pages, 22 figures, prepared for the 2015 EPJA Topical Issue on
"Exotic Matter in Neutron Stars"; v2 published version, discussions are
extende
Delineating the properties of matter in cold, dense QCD
The properties of dense QCD matter are delineated through the construction of
equations of state which should be consistent with QCD calculations in the low
and high density limits, nuclear laboratory experiments, and the neutron star
observations. These constraints, together with the causality condition of the
sound velocity, are used to develop the picture of hadron-quark continuity in
which hadronic matter continuously transforms into quark matter (modulo small
1st order phase transitions). For hadronic matter (at baryon density nB > ~2n0
with n0 ~ 0.16 fm^(-3) being the nuclear saturation density) we use equations
of state by Togashi et al. based on microscopic variational many-body
calculations, and for quark matter (nB > ~5n0) we construct equations of state
using a schematic quark model (with strangeness) whose interactions are
motivated by the hadron phenomenology. The region between hadronic and quark
matters (~2n0 < nB < ~5n0), which is most difficult to calculate, is treated by
highly constrained interpolation between nuclear and quark matter equations of
state. The resultant unified equation of state at zero temperature and
beta-equilibrium, which we call Quark-Hadron-Crossover (QHC18 and QHC19), is
consistent with the measured properties of neutron stars and in addition gives
us microscopic insights into the properties of dense QCD matter. In particular
to ~10n0 the gluons can remain as non-perturbative as in vacuum and the
strangeness can be as abundant as up- and down-quarks at the core of two-solar
mass neutron stars. Within our modeling the maximum mass is found less than
~2.35 times solar mass and the baryon density at the core ranges in ~5-8n0.Comment: 18 pages 11 figures, AIP Proceedings of the Xiamen-CUSTIPEN Workshop
on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave
Astronomy, Jan. 3-7, Xiamen, China; v2 references are adde
Quarkyonic Matter and Chiral Spirals
The nuclear matter, deconfined quark matter, and Quarkyonic matter in low
temperature region are classified based on the 1/Nc expansion. The chiral
symmetry in the Quarkyonic matter is investigated by taking into account
condensations of chiral particle-hole pairs. It is argued that the chiral
symmetry and parity are locally violated by the formation of chiral spirals, <
psibar exp(2 i mu z gamma^0 gamma^z) psi >. An extension to multiple chiral
spirals is also briefly discussed.Comment: Prepared for Hot Quark 2010, 4 page
The quark mass gap in strong magnetic fields
Quarks in strong magnetic fields (|eB|>>Lambda_QCD^2 ~ 0.04 GeV^2) acquire
enhanced infrared phase space proportional to |eB|. Accordingly they provide
larger chiral condensates and stronger backreactions to the gluon dynamics.
Confronting theories with lattice data at various values of |eB|, one can test
theoretical ideas as well as validity of various approximations, domain of
applicability of the effective models, and so on. The particularly interesting
findings on the lattice are inverse magnetic catalysis and linear growth of the
chiral condensate as a function of |eB|, which pose theoretical challenges. In
this talk we propose a scenario to explain both phenomena, claiming that the
quark mass gap should stay at around ~ Lambda_QCD, instead of ~|eB|^{1/2} which
has been supposed from dimensional arguments and/or effective model
calculations. The contrast between infrared and ultraviolet behaviors of the
interaction is a key ingredient to obtain the mass gap of ~Lambda_QCD.Comment: 4 pages, proceedings of the XXIV Quark Matter conference, May 19-24
2014, Darmstadt (Germany
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