281 research outputs found
Solving the Nose-Hoover thermostat for Nuclear Pasta
In this work we present a calculation of the hamiltonian variables solving
the molecular dynamics equations of motion for a system of nuclear matter
relevant to the description of nuclear pasta. The temperature is kept fixed by
using the Nos\'{e}-Hoover Thermostat and the interaction is modelled via a
semiclassical potential depending on both positions and momenta.Comment: 7 pages, 3 figures. Journal of Mathematical Chemistry, in pres
Constraining decaying dark matter with neutron stars
The amount of decaying dark matter, accumulated in the central regions in
neutron stars together with the energy deposition rate from decays, may set a
limit on the neutron star survival rate against transitions to more compact
objects provided nuclear matter is not the ultimate stable state of matter and
that dark matter indeed is unstable. More generally, this limit sets
constraints on the dark matter particle decay time, . We find that
in the range of uncertainties intrinsic to such a scenario, masses or and lifetimes s and
s can be excluded in the bosonic or fermionic
decay cases, respectively, in an optimistic estimate, while more
conservatively, it decreases by a factor . We
discuss the validity under which these results may improve with other current
constraints.Comment: 6 pages, 1 figure, matches published versio
Can Dark Matter explain the Braking Index of Neutron Stars?
We explore a new mechanism of slowing down the rotation of neutron stars via
accretion of millicharged dark matter.
We find that this mechanism yields pulsar braking indices that can be
substantially smaller than the standard of the magnetic dipole
radiation model for millicharged dark matter particles that are not excluded by
existing experimental constraints thus accommodating existing observations.Comment: 5 page
Strangelets and the TeV-PeV cosmic-ray anisotropies
Several experiments (e.g., Milagro and IceCube) have reported the presence in
the sky of regions with significant excess in the arrival direction
distributions of Galactic cosmic rays in the TeV to PeV energy range. Here we
study the possibility that these hotspots are a manifestation of the peculiar
nature of these cosmic rays, and of the presence of molecular clouds near the
sources. We propose that stable quark matter lumps or so-called "strangelets"
can be emitted in the course of the transition of a neutron star to a more
compact astrophysical object. A fraction of these massive particles would lose
their charge by spallation or electron capture in molecular clouds located in
the immediate neighborhood of their source, and propagate rectilinearly without
decaying further, hence inducing anisotropies of the order of the cloud size.
With reasonable astrophysical assumptions regarding the neutron star transition
rate, strangelet injection and neutralization rates, we can reproduce
successfully the observed hotspot characteristics and their distribution in the
sky.Comment: 5 pages, 1 figure, submitted to PR
Pulsar scintillation patterns and strangelets
We propose that interstellar extreme scattering events, usually observed as
pulsar scintillations, may be caused by a coherent agent rather than the
usually assumed turbulence of clouds. We find that the penetration of
a flux of ionizing, positively charged strangelets or quark nuggets into a
dense interstellar hydrogen cloud may produce ionization trails. Depending on
the specific nature and energy of the incoming droplets, diffusive propagation
or even capture in the cloud are possible. As a result, enhanced electron
densities may form and constitute a lens-like scattering screen for radio
pulsars and possibly for quasars.Comment: 5 pages, 2 figure
Dark matter, neutron stars and strange quark matter
We show that self-annihilating neutralino WIMP dark matter accreted onto
neutron stars may provide a mechanism to seed compact objects with long-lived
lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV.
This effect may trigger a conversion of most of the star into a strange star.
We use an energy estimate for the long-lived strangelet based on the Fermi gas
model combined with the MIT bag model to set a new limit on the possible values
of the WIMP mass that can be especially relevant for subdominant species of
massive neutralinos.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev. Let
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