3,109 research outputs found
Towards Understanding Astrophysical Effects of Nuclear Symmetry Energy
Determining the Equation of State (EOS) of dense neutron-rich nuclear matter
is a shared goal of both nuclear physics and astrophysics. Except possible
phase transitions, the density dependence of nuclear symmetry \esym is the most
uncertain part of the EOS of neutron-rich nucleonic matter especially at
supra-saturation densities. Much progresses have been made in recent years in
predicting the symmetry energy and understanding why it is still very uncertain
using various microscopic nuclear many-body theories and phenomenological
models. Simultaneously, significant progresses have also been made in probing
the symmetry energy in both terrestrial nuclear laboratories and astrophysical
observatories. In light of the GW170817 event as well as ongoing or planned
nuclear experiments and astrophysical observations probing the EOS of dense
neutron-rich matter, we review recent progresses and identify new challenges to
the best knowledge we have on several selected topics critical for
understanding astrophysical effects of the nuclear symmetry energy.Comment: 77 pages. Invited Review Article, EPJA (2019) in pres
Noise in Genotype Selection Model
We study the steady state properties of a genotype selection model in
presence of correlated Gaussian white noise. The effect of the noise on the
genotype selection model is discussed. It is found that correlated noise can
break the balance of gene selection and induce the phase transition which can
makes us select one type gene haploid from a gene group.Comment: 8 pages, 4 figure
Constraints on the symmetry energy from observational probes of the neutron star crust
A number of observed phenomena associated with individual neutron star
systems or neutron star populations find explanations in models in which the
neutron star crust plays an important role. We review recent work examining the
sensitivity to the slope of the symmetry energy of such models, and
constraints extracted on from confronting them with observations. We focus
on six sets of observations and proposed explanations: (i) The cooling rate of
the neutron star in Cassiopeia A, confronting cooling models which include
enhanced cooling in the nuclear pasta regions of the inner crust, (ii) the
upper limit of the observed periods of young X-ray pulsars, confronting models
of magnetic field decay in the crust caused by the high resistivity of the
nuclear pasta layer, (iii) glitches from the Vela pulsar, confronting the
paradigm that they arise due to a sudden re-coupling of the crustal neutron
superfluid to the crustal lattice after a period during which they were
decoupled due to vortex pinning, (iv) The frequencies of quasi-periodic
oscillations in the X-ray tail of light curves from giant flares from soft
gamma-ray repeaters, confronting models of torsional crust oscillations, (v)
the upper limit on the frequency to which millisecond pulsars can be spun-up
due to accretion from a binary companion, confronting models of the r-mode
instability arising above a threshold frequency determined in part by the
viscous dissipation timescale at the crust-core boundary, and (vi) the
observations of precursor electromagnetic flares a few seconds before short
gamma-ray bursts, confronting a model of crust shattering caused by resonant
excitation of a crustal oscillation mode by the tidal gravitational field of a
companion neutron star just before merger.Comment: 19 pages, 10 figure and 1 tabl
Super-soft symmetry energy encountering non-Newtonian gravity in neutron stars
Considering the non-Newtonian gravity proposed in the grand unification
theories, we show that the stability and observed global properties of neutron
stars can not rule out the super-soft nuclear symmetry energies at
supra-saturation densities. The degree of possible violation of the
Inverse-Square-Law of gravity in neutron stars is estimated using an Equation
of State (EOS) of neutron-rich nuclear matter consistent with the available
terrestrial laboratory data.Comment: Version accepted by Physical Review Letter
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