733 research outputs found
The Implications of Galaxy Formation Models for the TeV Observations of Current Detectors
This paper represents a step toward constraining galaxy formation models via
TeV gamm a ray observations. We use semi-analytic models of galaxy formation to
predict a spectral distribution for the intergalactic infrared photon field,
which in turn yields information about the absorption of TeV gamma rays from
extra-galactic sources. By making predictions for integral flux observations at
>200 GeV for several known EGRE T sources, we directly compare our models with
current observational upper limits obtained by Whipple. In addition, our
predictions may offer a guide to the observing programs for the current
population of TeV gamma ray observatories.Comment: 6 pages, 11 figures, to appear in the proceedings of the 6th TeV
Workshop at Snowbird, U
Sizes of Voids as a test for Dark Matter Models
We use the void probability statistics to study the redshift-space galaxy
distribution as described by a volume-limited subsample of the Perseus-Pisces
survey. We compare the results with the same analysis realized on artificial
samples, extracted from high-resolution N-body simulations by reproducing the
observational biases of the real data set. Simulations are run for the
Cold+HotDM model (CHDM) and for unbiased and biased (b=1.5) CDM models in a 50
Mpc/h box. We identify galaxies as residing in peaks of the evolved density
field. We fragment overmerged structures into individual galaxies so as to
reproduce both the correct luminosity function (after assuming M/ L values for
the resulting galaxy groups) and the two-point correlation function. Our main
result is that a void-probability function (VPF) from the standard CHDM model
with fractions 60% cold, 30% hot, 10% barions, exceeds the observational VPF
with a high confidence level. CDM models produce smaller VPF independent of the
biasing parameter. We verify the robustness of this result against changing the
observer position in the simulations and the galaxy identification in the
evolved density field.Comment: 15 pages, postscrip
Degenerate Fermi gas perturbations at standard background cosmology
The hypothesis of a tiny fraction of the cosmic inventory evolving
cosmologically as a degenerate Fermi gas test fluid at some dominant
cosmological background is investigated. Our analytical results allow for
performing preliminary computations to the evolution of perturbations for
relativistic and non-relativistic test fluids. The density fluctuation,
, the fluid velocity divergence, , and an explicit expression
for the dynamics of the shear stress, , are obtained for a degenerate
Fermi gas in the background regime of radiation. Extensions to the dominance of
matter and to the CDM cosmological background are also investigated
and lessons concerning the formation of large structures of degenerate Fermi
gas are depicted.Comment: 20 pages, 4 figure
Phenomenology of Neutrino Oscillations
The phenomenology of solar, atmospheric, supernova and laboratory neutrino
oscillations is described. Analytical formulae for matter effects are reviewed.
The results from oscillations are confronted with neutrinoless double beta
decay.Comment: 11 pages, 2 figures, latex, Plenary talk given at Workshop in High
Energy Particle Physics-6, Chennai, Indi
CP and T violation test in neutrino oscillation
We examine how large violation of CP and T is allowed in long base line
neutrino experiments. When we attribute only the atmospheric neutrino anomaly
to neutrino oscillation we may have large CP violation effect. When we
attribute both the atmospheric neutrino anomaly and the solar neutrino deficit
to neutrino oscillation we may have a sizable T violation effect proportional
to the ratio of two mass differences; it is difficult to see CP violation since
we can't ignore the matter effect. We give a simple expression for T violation
in the presence of matter.Comment: 12 pages + 2 eps figures, Latex, In order to avoid misunderstanding
we have refined our English and rewritten the parts which might be
misleading. Several typographical errors are correcte
Constraints on non-thermal Dark Matter from Planck lensing extraction
Distortions of CMB temperature and polarization anisotropy maps caused by
gravitational lensing, observable with high angular resolution and sensitivity,
can be used to constrain the sterile neutrino mass, offering several advantages
against the analysis based on the combination of CMB, LSS and Ly\alpha forest
power spectra. As the gravitational lensing effect depends on the matter
distribution, no assumption on light-to-mass bias is required. In addition,
unlike the galaxy clustering and Ly\alpha forest power spectra, the projected
gravitational potential power spectrum probes a larger range of angular scales,
the non-linear corrections being required only at very small scales. Taking
into account the changes in the time-temperature relation of the primordial
plasma and the modification of the neutrino thermal potential, we compute the
projected gravitational potential power spectrum and its correlation with the
temperature in the presence of DM sterile neutrino. We show that the
cosmological parameters are generally not biased when DM sterile neutrino is
included. From this analysis we found a lower limit on DM sterile neutrino mass
m_s >2.08 keV at 95% CL, consistent with the lower mass limit obtained from the
combined analysis of CMB, SDSS 3D power spectrum and SDSS Ly\alpha forest power
spectrum ( keV). We conclude that although the information that
can be obtained from lensing extraction is rather limited due to the high level
of the lensing noise of Planck experiment, weak lensing of CMB offers a
valuable alternative to constrain the dark matter sterile neutrino mass.Comment: 15 pages, 6 figure
Semiclassical Treatment of Diffraction in Billiard Systems with a Flux Line
In billiard systems with a flux line semiclassical approximations for the
density of states contain contributions from periodic orbits as well as from
diffractive orbits that are scattered on the flux line. We derive a
semiclassical approximation for diffractive orbits that are scattered once on a
flux line. This approximation is uniformly valid for all scattering angles. The
diffractive contributions are necessary in order that semiclassical
approximations are continuous if the position of the flux line is changed.Comment: LaTeX, 17 pages, 4 figure
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