637 research outputs found
Spontaneous symmetry breaking for long-wave gravitons in the early Universe
It is shown that nonlinear terms in equations of gravitons on the background
of curved space-time of the expanding Universe can solve the problem of the
negative square of the effective mass formally arising in linear approximation
for gravitons. Similar to well known spontaneous breaking of symmetry in
Goldstone model one must take another vacuum so that nonzero vacuum expectation
value of the quantized graviton field leads to change of spectrum for
gravitons. There appears two graviton fields, one with the positive mass,
another with the zero mass. Energy density and the density of particles created
by gravitation of the expanding Universe are calculated for some special cases
of the scale factor. Numerical results are obtained for the dust universe case.Comment: 13 page
Pulsar Kicks With Sterile Neutrinos and Landau Levels
We use a model with two sterile neutrinos obtained by fits to the MiniBoone
and LSND experiments. Using formulations with neutrinos created by URCA
Processes in a strong magnetic field, so the lowest Landau level has a sizable
probability, we find that with known paramenters the assymetric sterile
neutrino emissivity might account for large pulsar kicks.Comment: 3 pages, 1 figur
Radiative Effects in the Standard Model Extension
The possibility of radiative effects induced by the Lorentz and CPT
non-invariant interaction term for fermions in the Standard Model Extension is
investigated. In particular, electron-positron photo-production and photon
emission by electrons and positrons are studied. The rates of these processes
are calculated in the Furry picture. It is demonstrated that the rates obtained
in the framework of the model adopted strongly depend on the polarization
states of the particles involved. As a result, ultra-relativistic particles
produced should occupy states with a preferred spin orientation, i.e., photons
have the sign of polarization opposite to the sign of the effective potential,
while charged particle are preferably in the state with the helicity coinciding
with the sign of the effective potential. This leads to evident spatial
asymmetries which may have certain consequences observable at high energy
accelerators, and in astrophysical and cosmological studies.Comment: 10 pages, 2 figures, Revtex4, to appear in Phys.Rev.D, misprints are
correcte
The Halo Beaming Model for Gamma-Ray Bursts
We consider a model for gamma-ray bursts (GRBs) from high-velocity neutron
stars in the galactic halo. In this model, bursters are born in the galactic
disk with large recoil velocities V_r, and GRBs are beamed to within emission
cones of half-angle \phi centered on V_r. We describe scenarios for
magnetically -channeled GRBs that have such beaming characteristics. We then
make detailed comparisons of this halo beaming model (HBM) to BATSE and PVO
data for GRB intensity & angular position distributions. Acceptable fits to
observations of over 1000 bursts are obtained for \phi = 15 - 30 degrees and
for a BATSE sampling depth ~ 180 kpc. Present data favor a truly isotropic
(cosmological) model over the HBM, but not by a statistically compelling
margin. Bursters born in nearby external galaxies, such as M31, are almost
entirely undetectable in the HBM because of misdirected beaming. We analyze
several refinements of the basic HBM: gamma-ray intensities that vary with
angle from the beam axis; non-standard-candle GRB luminosity functions; and
models including a subset of bursters that do not escape from the galaxy. We
also discuss the energy budgets for the bursters, the origins of their recoils,
and the physics of burst beaming and alignment. One possible physical model is
based on the magnetar model of soft gamma repeaters (SGRs). Empirical bounds on
the rate of formation and peculiar velocities of SGRs imply that there exist ~
10^4 to ~ 10^7 aged SGRs in the galactic halo within a distance of 100 kpc. The
HBM gives an acceptable fit to observations only if it satisfies certain
conditions (e.g. \phi ~ 20 deg) which are possible, but for which there exist
no clear & compelling theoretical justifications. The cosmological burster
hypothesis is more generic and thus more attractive in this sense. (Abbreviated
Abstract).Comment: ApJ accepted, 9 figures, AASTE
The DRIFT Dark Matter Experiments
The current status of the DRIFT (Directional Recoil Identification From
Tracks) experiment at Boulby Mine is presented, including the latest limits on
the WIMP spin-dependent cross-section from 1.5 kg days of running with a
mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with
ongoing work towards DRIFT III, which aims to be the world's first 10 m3-scale
directional Dark Matter detector.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
The cusp effect in eta' --> eta pi pi decays
Strong final-state interactions create a pronounced cusp in eta' --> eta pi0
pi0 decays. We adapt and generalize the non-relativistic effective field theory
framework developed for the extraction of pi pi scattering lengths from K --> 3
pi decays to this case. The cusp effect is predicted to have an effect of more
than 8% on the decay spectrum below the pi+ pi- threshold.Comment: 11 pages, 8 figures; comment added, typos corrected, version
published in Eur. Phys. J.
A search for J^{PC}=1^{-+} exotic mesons in the pi- pi- pi+ and pi- pi0 pi0 systems
A partial wave analysis (PWA) of the pi-pi-pi+ and pi-pi0pi0 systems produced
in the reaction pi- p -> (3pi)-p at 18 GeV/c was carried out using an isobar
model assumption. This analysis is based on 3.0M pi-pi0pi0 events and 2.6M
pi-pi-pi+ events and shows production of the a2(1320), pi2(1670) and \pi(1800)
mesons. An earlier analysis of 250K pi-pi-pi+ events from the same experiment
showed possible evidence for a J^{PC}=1^{-+}$ exotic meson with a mass of 1.6
GeV/c^2 decaying into rho pi. In this analysis of a higher statistics sample of
the (3pi)- system in two charged modes we find no evidence of an exotic meson.Comment: 4 pages, 5 figures, added comment about the negative reflectivity
exotic wave
Distribution, Abundance, and Epidemiological Significance of <I>Ixodes ricinus</I> Ticks in the Territory of the Tula Region
Based on the analysis of the information concerning distribution and abundance of Ixodidae ticks in the territory of the Tula Region (1998-2012), obtained have been the new data on the expansion of I. ricinus habitat. Results of phyto-geographical zoning of the region have served as a landscape base for investigation of regularities as regards spatial distribution of the species. Specified have been the territories with low, medium, and high population density rate. Biotopes with the most favorable environmental conditions for the species are situated in the mixed woods of the Prioksky region and broad-leaved forests - of the Zasechny one. As for the forest-steppe areas, optimum biotopes are localized in the highland and steppificated oakwoods in the south of South-Eastern Region. Thus it has been established that in the recent decade I. ricinus ticks can be found not only in the forest areas, but in the forest-steppe ones too. This may be related to the increase in their numbers under favorable environmental conditions, reduction of farming lands, and shrub invasion. Average value for I. ricinus numbers in the forest area reaches 39.4 specimen/flag-kilometer; in the forest-steppe zone - 23.7 specimen/flag-kilometer. Identified have been potentially hazardous territories as regards natural-focal tick-borne infections, the agent circulation and transmission of which is sustained by I. ricinus. The finding in its turn sets the grounds for carrying out specific epizootiological surveillance and regulation of preventive measures
Search for decay with VES detector
The isospin violating decay has been studied at
VES facility. This study is based at the statistics acquired in
interactions at 27, 36.6 and 41 GeV/c in diffractive reaction . The decay is observed. The ratio of
decay probabilities to is .Comment: 10 pages, 8 figures, presented at XII Conference on Hadron
Spectroscop
Cold War, ‘Thaw’ and ‘Everlasting Friendship’: Soviet Mountaineers and Mount Everest, 1953–1960
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