4,445 research outputs found
Radiative transitions of high energy neutrino in dense matter
The quantum theory of the ``spin light'' (electromagnetic radiation emitted
by a massive neutrino propagating in dense matter due to the weak interaction
of a neutrino with background fermions) is developed. In contrast to the
Cherenkov radiation, this effect does not disappear even if the medium
refractive index is assumed to be equal to unity. The formulas for the
transition rate and the total radiation power are obtained. It is found out
that radiation of photons is possible only when the sign of the particle
helicity is opposite to that of the effective potential describing the
interaction of a neutrino (antineutrino) with the background medium. Due to the
radiative self-polarization the radiating particle can change its helicity. As
a result, the active left-handed polarized neutrino (right-handed polarized
antineutrino) converting to the state with inverse helicity can become
practically ``sterile''. Since the sign of the effective potential depends on
the neutrino flavor and the matter structure, the ``spin light'' can change a
ratio of active neutrinos of different flavors. In the ultra relativistic
approach, the radiated photons averaged energy is equal to one third of the
initial neutrino energy, and two thirds of the energy are carried out by the
final ``sterile'' neutrinos. This fact can be important for the understanding
of the ``dark matter'' formation mechanism on the early stages of evolution of
the Universe.Comment: 7 pages, latex, one misprint in eq. 12 correcte
Theory of condensation of indirect excitons in a trap
We present theoretical studies of condensation of indirect excitons in a
trap. Our model quantifies the effect of screening of the trap potential by
indirect excitons on exciton condensation. The theoretical studies are applied
to a system of indirect excitons in a GaAs/AlGaAs coupled quantum well
structure in a diamond-shaped electrostatic trap where exciton condensation was
studied in earlier experiments. The estimated condensation temperature of the
indirect excitons in the trap reaches hundreds of milliKelvin
Does the Borexino experiment have enough resolution to detect the neutrino flavor day-night asymmetry?
The Earth's density distribution can be approximately considered piecewise
continuous at the scale of two-flavor oscillations of neutrinos with energies
about 1 MeV. This quite general assumption appears to be enough to analytically
calculate the day-night asymmetry factor. Using the explicit time averaging
procedure, we show that, within the leading-order approximation, this factor is
determined by the electron density immediately before the detector, i.e. in the
Earth's crust. Within the approximation chosen, the resulting asymmetry factor
does not depend either on the properties of the inner Earth's layers or on the
substance and the dimensions of the detector. For beryllium neutrinos, we
arrive at the asymmetry factor estimation of about , which
is at least one order of magnitude beyond the present experimental resolution,
including that of the Borexino experiment.Comment: 16 pages, 3 figures; Talk given at the 17th International Seminar on
High Energy Physics "QUARKS'2012" (Yaroslavl, Russia, June 4-10, 2012); to
appear in the Proceedings volum
CHOOSING THERAPEUTIC TACTICS FOR OPEN CHEST WOUNDS: THE VALUE OF THORACOSCOPY
Results of 163 thoracoscopic examinations for thoracic trauma are presented. In all cases, the the cause of the injury was stabbing. Among the patients, there were 147 men (90.2 %) and 17 women (9.8 %). Thoracoscopy was performed under local anesthesia or endotracheal anesthesia (predominantly), in a semi-lateral position on the healthy side with a reliable fixation of the patient, which is necessary, since it sometimes there is need to change the position of the table. The first thoracoport was usually introduced into the 5th intercostal space. After the revision of the pleural cavity, according to the indications, places of additional punctures and the introduction of appropriate instruments were determined. For evacuation of blood from the pleural cavity an electric pump was used. For hemostasis, electrocoagulation was commonly applied, and in a number of cases we used the haemostatic sponge. To stop bleeding from the lung tissue, as well as for aerostasis, the Roeder loop was used. After thoracoscopy, the question of further tactics was resolved. With ineffective thoracoscopy, thoracotomy was required. In case of successful thoracoscopy, the operation was finished with draining the pleural cavity through the most adequately located punctures. Thoracoscopy is an effective method of determining further tactics in this pathology. With a trauma in the "danger zone", 41 of 62 patients managed to avoid conversion. In many cases thoracoscopy allows to perform hemostasis, aerostasis and other curative measures. It also can reduce the amount of thoracotomy by 2-2.5 time
Multi-frequency investigation of the parsec- and kilo-parsec-scale radio structures in high-redshift quasar PKS 1402+044
We investigate the frequency-dependent radio properties of the jet of the
luminous high-redshift (z = 3.2) radio quasar PKS 1402+044 (J1405+0415) by
means of radio interferometric observations. The observational data were
obtained with the VLBI Space Observatory Programme (VSOP) at 1.6 and 5 GHz,
supplemented by other multi-frequency observations with the Very Long Baseline
Array (VLBA; 2.3, 8.4, and 15 GHz) and the Very Large Array (VLA; 1.4, 5, 15,
and 43 GHz). The observations span a period of 7 years. We find that the
luminous high-redshift quasar PKS 1402+044 has a pronounced "core-jet"
morphology from the parsec to the kilo-parsec scales. The jet shows a steeper
spectral index and lower brightness temperature with increasing distance from
the jet core. The variation of brightness temperature agrees well with the
shock-in-jet model. Assuming that the jet is collimated by the ambient magnetic
field, we estimate the mass of the central object as ~10^9 M_sun. The upper
limit of the jet proper motion of PKS 1402+044 is 0.03 mas/yr (~3c) in the
east-west direction.Comment: 9 pages, 6 figures
On the possibility of refining by means of optical location some astronomical parameters of the system - Earth-Moon
Optical location of moon in Earth-Moon system using artificial light reflector, on lunar surfac
Neutrino spin rotation in dense matter and electromagnetic field
Exact solutions of the Dirac--Pauli equation for massive neutrino with
anomalous magnetic moment interacting with dense matter and strong
electromagnetic field are found. The complete system of neutrino wavefunctions,
which show spin rotation properties are obtained and their possible
applications are discussed.Comment: 11 pages, latex, misprints are correcte
High--Resolution 3D Simulations of Relativistic Jets
We have performed high-resolution 3D simulations of relativistic jets with
beam flow Lorentz factors up to 7, a spatial resolution of 8 cells per beam
radius, and for up to 75 normalized time units to study the morphology and
dynamics of 3D relativistic jets. Our simulations show that the coherent fast
backflows found in axisymmetric models are not present in 3D models. We further
find that when the jet is exposed to non-axisymmetric perturbations, (i) it
does not display the strong perturbations found for 3D classical hydrodynamic
and MHD jets (at least during the period of time covered by our simulations),
and (ii) it does propagate according to the 1D estimate. Small 3D effects in
the relativistic beam give rise to a lumpy distribution of apparent speeds like
that observed in M87. The beam is surrounded by a boundary layer of high
specific internal energy. The properties of this layer are briefly discussed.Comment: 15 pages, 4 figures. Accepted to be publish in the ApJ Letters.
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