546 research outputs found
Big Bang Nucleosynthesis with Independent Neutrino Distribution Functions
We have performed new Big Bang Nucleosynthesis calculations which employ
arbitrarily-specified, time-dependent neutrino and antineutrino distribution
functions for each of up to four neutrino flavors. We self-consistently couple
these distributions to the thermodynamics, the expansion rate and scale
factor-time/temperature relationship, as well as to all relevant weak,
electromagnetic, and strong nuclear reaction processes in the early universe.
With this approach, we can treat any scenario in which neutrino or antineutrino
spectral distortion might arise. These scenarios might include, for example,
decaying particles, active-sterile neutrino oscillations, and active-active
neutrino oscillations in the presence of significant lepton numbers. Our
calculations allow lepton numbers and sterile neutrinos to be constrained with
observationally-determined primordial helium and deuterium abundances. We have
modified a standard BBN code to perform these calculations and have made it
available to the community.Comment: 9 pages, 5 figure
Sterile neutrinos, dark matter, and the pulsar velocities in models with a Higgs singlet
We identify the range of parameters for which the sterile neutrinos can
simultaneously explain the cosmological dark matter and the observed velocities
of pulsars. To satisfy all cosmological bounds, the relic sterile neutrinos
must be produced sufficiently cold. This is possible in a class of models with
a gauge-singlet Higgs boson coupled to the neutrinos. Sterile dark matter can
be detected by the x-ray telescopes. The presence of the singlet in the Higgs
sector can be tested at the Large Hadron Collider.Comment: 4 pages, one figur
Dark matter sterile neutrinos in stellar collapse: alteration of energy/lepton number transport and a mechanism for supernova explosion enhancement
We investigate matter-enhanced Mikheyev-Smirnov-Wolfenstein (MSW)
active-sterile neutrino conversion in the
channel in the collapse of the iron core of a pre-supernova star. For values of
sterile neutrino rest mass and vacuum mixing angle
(specifically, ) which include those required for viable sterile neutrino
dark matter, our one-zone in-fall phase collapse calculations show a
significant reduction in core lepton fraction. This would result in a smaller
homologous core and therefore a smaller initial shock energy, disfavoring
successful shock re-heating and the prospects for an explosion. However, these
calculations also suggest that the MSW resonance energy can exhibit a minimum
located between the center and surface of the core. In turn, this suggests a
post-core-bounce mechanism to enhance neutrino transport and neutrino
luminosities at the core surface and thereby augment shock re-heating: (1)
scattering-induced or coherent MSW conversion occurs deep in
the core, at the first MSW resonance, where energies are large ( MeV); (2) the high energy stream outward at near light speed; (3)
they deposit their energy when they encounter the second MSW resonance
just below the proto-neutron star surface.Comment: 13 pages, 9 figure
Where to find a dark matter sterile neutrino?
We propose a strategy of how to look for dark matter (DM) particles
possessing a radiative decay channel and derive constraints on their parameters
from observations of X-rays from our own Galaxy and its dwarf satellites. When
applied to the sterile neutrinos in keV mass range, it allows a significant
improvement of restrictions to its parameters, as compared with previous works.Comment: 5 pp, revtex; v3: 1-sigma limits have been replaced by more
conservative 3-sigma limits, a picture illustrating the data analysis methods
has been ade
On the hadronic contribution to sterile neutrino production
Sterile neutrinos with masses in the keV range are considered to be a viable
candidate for warm dark matter. The rate of their production through
active-sterile neutrino transitions peaks, however, at temperatures of the
order of the QCD scale, which makes it difficult to estimate their relic
abundance quantitatively, even if the mass of the sterile neutrino and its
mixing angle were known. We derive here a relation, valid to all orders in the
strong coupling constant, which expresses the production rate in terms of the
spectral function associated with active neutrinos. The latter can in turn be
expressed as a certain convolution of the spectral functions related to various
mesonic current-current correlation functions, which are being actively studied
in other physics contexts. In the naive weak coupling limit, the appropriate
Boltzmann equations can be derived from our general formulae.Comment: 28 pages. v2: small clarifications added, published versio
Anomalous Maxwell equations for inhomogeneous chiral plasma
Using the chiral kinetic theory we derive the electric and chiral current
densities in inhomogeneous relativistic plasma. We also derive equations for
the electric and chiral charge chemical potentials that close the Maxwell
equations in such a plasma. The analysis is done in the regimes with and
without a drift of the plasma as a whole. In addition to the currents present
in the homogeneous plasma (Hall current, chiral magnetic, chiral separation,
and chiral electric separation effects, as well as Ohm's current) we derive
several new terms associated with inhomogeneities of the plasma. Apart from
various diffusion-like terms, we find also new dissipation-less terms that are
independent of relaxation time. Their origin can be traced to the Berry
curvature modifications of the kinetic theory.Comment: 16 pages; published versio
Sterile neutrinos in cosmology and how to find them in the lab
A number of observed phenomena in high energy physics and cosmology lack
their resolution within the Standard Model of particle physics. These puzzles
include neutrino oscillations, baryon asymmetry of the universe and existence
of dark matter. We discuss the suggestion that all these problems can be solved
by new physics which exists only below the electroweak scale. The dedicated
experiments that can confirm or rule out this possibility are discussed.Comment: Invited talk at XXIII Int. Conf. on Neutrino Physics and
Astrophysics, May 25-31, Christchurch, New Zealan
Long-range magnetic fields in the ground state of the Standard Model plasma
In thermal equilibrium the ground state of the plasma of Standard Model
particles is determined by temperature and exactly conserved combinations of
baryon and lepton numbers. We show that at non-zero values of the global
charges a translation invariant and homogeneous state of the plasma becomes
unstable and the system transits into a new state, containing a large-scale
magnetic field. The origin of this effect is the parity-breaking character of
weak interactions and chiral anomaly. This situation can occur in the early
Universe and may play an important role in its subsequent evolution.Comment: 6 pages. Comments are welcom
Sterile Neutrino-Enhanced Supernova Explosions
We investigate the enhancement of lepton number, energy, and entropy
transport resulting from active-sterile neutrino conversion
deep in the post-bounce supernova core followed by re-conversion
further out, near the neutrino sphere. We explicitly take
account of shock wave and neutrino heating modification of the active neutrino
forward scattering potential which governs sterile neutrino production. We find
that the luminosity at the neutrino sphere could be increased by
between and during the crucial shock re-heating epoch
if the sterile neutrino has a rest mass and vacuum mixing parameters in ranges
which include those required for viable sterile neutrino dark matter. We also
find sterile neutrino transport-enhanced entropy deposition ahead of the shock.
This `` pre-heating\rq\rq can help melt heavy nuclei and thereby reduce the
nuclear photo-dissociation burden on the shock. Both neutrino luminosity
enhancement and pre-heating could increase the likelihood of a successful core
collapse supernova explosion.Comment: 12 pages, 4 figure
Light-cone Superstring Field Theory, pp-wave background and integrability properties
We show that the three strings vertex coefficients in light--cone open string
field theory satisfy the Hirota equations for the dispersionless Toda lattice
hierarchy. We show that Hirota equations allow us to calculate the correlators
of an associated quantum system where the Neumann coefficients represent the
two--point functions. We consider next the three strings vertex coefficients of
the light--cone string field theory on a maximally supersymmetric pp--wave
background. Using the previous results we are able to show that these Neumann
coefficients satisfy the Hirota equations for the full Toda lattice hierarchy
at least up to second order in the 'string mass' .Comment: 23 pages, 3 figures, footnote and references adde
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