3,820 research outputs found
Diquark Condensates and Compact Star Cooling
The effect of color superconductivity on the cooling of quark stars and
neutron stars with large quark cores is investigated. Various known and new
quark-neutrino processes are studied. As a result, stars being in the color
flavor locked (CFL) color superconducting phase cool down extremely fast. Quark
stars with no crust cool down too rapidly in disagreement with X-ray data. The
cooling of stars being in the N_f =2 color superconducting (2SC) phase with a
crust is compatible with existing X-ray data. Also the cooling history of stars
with hypothetic pion condensate nuclei and a crust does not contradict the
data.Comment: 10 pages, 5 figures, accepted for publication in Ap
Constraining strangeness in dense matter with GW170817
Particles with strangeness content are predicted to populate dense matter,
modifying the equation of state of matter inside neutron stars as well as their
structure and evolution. In this work, we show how the modeling of strangeness
content in dense matter affects the properties of isolated neutrons stars and
the tidal deformation in binary systems. For describing nucleonic and hyperonic
stars we use the many-body forces model (MBF) at zero temperature, including
the mesons for the description of repulsive hyperon-hyperon
interactions. Hybrid stars are modeled using the MIT Bag Model with vector
interaction (vMIT) in both Gibbs and Maxwell constructions, for different
values of bag constant and vector interaction couplings. A parametrization with
a Maxwell construction, which gives rise to third family of compact stars (twin
stars), is also investigated. We calculate the tidal contribution that adds to
the post-Newtonian point-particle corrections, the associated love number for
sequences of stars of different composition (nucleonic, hyperonic, hybrid and
twin stars), and determine signatures of the phase transition on the
gravitational waves in the accumulated phase correction during the inspirals
among different scenarios for binary systems. On the light of the recent
results from GW170817 and the implications for the radius of
stars, our results show that hybrid stars can
only exist if a phase transition takes place at low densities close to
saturation
Capture of Leptophilic Dark Matter in Neutron Stars
Dark matter particles will be captured in neutron stars if they undergo
scattering interactions with nucleons or leptons. These collisions transfer the
dark matter kinetic energy to the star, resulting in appreciable heating that
is potentially observable by forthcoming infrared telescopes. While previous
work considered scattering only on nucleons, neutron stars contain small
abundances of other particle species, including electrons and muons. We perform
a detailed analysis of the neutron star kinetic heating constraints on
leptophilic dark matter. We also estimate the size of loop induced couplings to
quarks, arising from the exchange of photons and Z bosons. Despite having
relatively small lepton abundances, we find that an observation of an old,
cold, neutron star would provide very strong limits on dark matter interactions
with leptons, with the greatest reach arising from scattering off muons. The
projected sensitivity is orders of magnitude more powerful than current dark
matter-electron scattering bounds from terrestrial direct detection
experiments.Comment: 26 pages, 8 figures, 3 tables, 2 appendices. Discussion extended,
references added, matches JCAP published versio
RXJ1856.5-3754 and RXJ0720.4-3125 are P-Stars
P-stars are a new class of compact stars made of up and down quarks in
-equilibrium with electrons in a chromomagnetic condensate. P-stars are
able to account for compact stars with , as well as stars
comparable to canonical neutron stars. We show that P-stars once formed are
absolutely stable, for they cannot decay into neutron or strange stars. We
convincingly argue that the nearest isolated compact stars RXJ1856.5-3754 and
RXJ0720.4-3125 could be interpreted as P-stars with
and .Comment: 18 pages, 2 figures, revised version, to appear in JCA
Half-Skyrmions and the Equation of State for Compact-Star Matter
The half-skyrmions that appear in dense baryonic matter when skyrmions are
put on crystals modify drastically hadron properties in dense medium and affect
strongly the nuclear tensor forces, thereby influencing the equation of state
(EoS) of dense nuclear and asymmetric nuclear matter. The matter comprised of
half skyrmions has vanishing quark condensate but non-vanishing pion decay
constant and could be interpreted as a hadronic dual of strong-coupled quark
matter. We infer from this observation combined with certain predictions of
hidden local symmetry in low-energy hadronic interactionsa a set of new scaling
laws -- called "new-BR" -- for the parameters in nuclear effective field theory
controlled by renormalization-group flow. They are subjected to the EoS of
symmetric and asymmetric nuclear matter, and are then applied to nuclear
symmetry energies and properties of compact stars. The changeover from the
skyrmion matter to a half-skyrmion matter that takes place after the cross-over
density provides a simple and natural field theoretic explanation for
the change of the EoS from soft to stiff at a density above that of nuclear
matter required for compact stars as massive as . Cross-over
density in the range 1.5n_0 \lsim n_{1/2} \lsim 2.0 n_0 has been employed,
and the possible skyrmion half-skyrmion coexistence {or cross-over} near
is discussed. The novel structure of {the tensor forces and} the EoS
obtained with the new-BR scaling is relevant for neutron-rich nuclei and
compact star matter and could be studied in RIB (rare isotope beam) machines.Comment: 12 pages, 7 figures, slightly revised for PRC, in pres
Neutron star cooling constraints for color superconductivity in hybrid stars
We apply the recently developed Log N - Log S test of compact star cooling
theories for the first time to hybrid stars with a color superconducting quark
matter core. While there is not yet a microscopically founded superconducting
quark matter phase which would fulfill constraints from cooling phenomenology,
we explore the hypothetical 2SC+X phase and show that the magnitude and
density-dependence of the X-gap can be chosen to satisfy a set of tests:
temperature - age (T - t), the brightness constraint, Log N - Log S, and the
mass spectrum constraint. The latter test appears as a new conjecture from the
present investigation.Comment: 10 pages, 9 figures, 1 tabl
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