10,086 research outputs found
Production of pair in electron-positron annihilation in the Nambu-Jona-Lasinio model
The process is described in the framework of the
expanded NJL model in the energy region from 0.9 GeV to 1.5 GeV. The
contribution of intermediate state with vector mesons , and , where is the first radial
excitation of - meson was taken into account. Results obtained are in
satisfactory agreement with experimental data.Comment: 5 pages, 1 figure, 1 tabl
Synchronization in the BCS Pairing Dynamics as a Critical Phenomenon
Fermi gas with time-dependent pairing interaction hosts several different
dynamical states. Coupling between the collective BCS pairing mode and
individual Cooper pair states can make the latter either synchronize or
dephase. We describe transition from phase-locked undamped oscillations to
Landau-damped dephased oscillations in the collisionless, dissipationless
regime as a function of coupling strength. In the dephased regime, we find a
second transition at which the long-time asymptotic pairing amplitude vanishes.
Using a combination of numerical and analytical methods we establish a
continuous (type II) character of both transitions
rho(omega)-> pi^0 pi^0 gamma, rho(omega) -> eta pi^0 gamma decays in the local quark Nambu--Jona-Lasinio model
The branching ratios and photon spectra of the rare processes rho(omega)->
pi^0 pi^0 gamma, rho(omega) -> eta pi^0 gamma are calculated in the framework
of the standard local quark Nambu--Jona-Lasinio (NJL) model. Three types of
diagrams are considered: the quark box and the pole diagrams with scalar
(sigma,a_0(980)) and vector (rho,omega) mesons. The obtained estimations for
the widths of the processes rho(omega)-> pi^0 pi^0 gamma are in satisfactory
agreement with existing experimental data. Predictions are made for the widths
of the processes rho(omega) -> eta pi^0 gamma.Comment: 6 pages, 5 figure
Two-photon decays of vector mesons and dilepton decays of scalar mesons in dense matter
Two-photon decays of vector mesons and dilepton decays of scalar mesons which
are forbidden in vacuum and can occur in dense baryonic matter due to the
explicit violation of Lorentz symmetry are described within a quark model of
the Nambu--Jona-Lasinio type. The temperature and chemical potential dependence
of these processes is investigated. It is found that their contribution to the
production of photons and leptons in heavy-ion collisions is enhanced near the
conditions corresponding to the restoration of chiral symmetry. Moreover, in
the case of the a_0 meson and especially the \rho-meson, a resonant behaviour
(an additional amplification) is observed due to the degeneration of \rho and
a_0 masses when a hot hadron matter is approaching a chirally symmetric phase.Comment: 20 figures, IOP styl
Relativistic particle dynamics in D=2+1
We propose a SUSY variant of the action for a massless spinning particles via
the inclusion of twistor variables. The action is constructed to be invariant
under SUSY transformations and -reparametrizations even when an
interaction field is including. The constraint analysis is achieved and the
equations of motion are derived. The commutation relations obtained for the
commuting spinor variables show that the particle states have
fractional statistics and spin. At once we introduce a possible massive term
for the non-interacting model.Comment: 11 page
Particle Spectra and Mass Composition in the Ultra-High Energy Region in the Framework of the Galactic Origin of Cosmic Rays
The possibility for a self-consistent description of all the basic features
of the observed cosmic ray spectra and primary composition variations in the
energy range of eV within the Galactic origin scenario is
examined.
We assume the existence of Galactic sources that accelerate particles up to
eV and take into account a highly inhomogeneous
(fractal-like) distribution of matter and magnetic fields in the Galaxy that
leads to extremely large free paths of particles ("L\'{e}vy flights"), along
with an overwhelming contribution to the cosmic ray fluxes observed above eV from particles reaching the Solar System without scattering. Our
scenario was refined on the basis of recent experimental results on primary
mass composition. Model predictions, which could be verified with the improved
high-precision measurements in the nearest future are discussed.Comment: 5 pages, 2 figures, 19th International Symposium on Very High Energy
Cosmic Ray Interactions (22-27 August 2016). Moscow, Russia. P.N. Lebedev
Physical Institute of the Russian Academy of Sciences (LPI RAS
Anomalous transport in normal-superconducting and ferromagnetic-superconducting nanostructures
We have calculated the temperature dependence of the conductance variation
() of mesoscopic superconductor normal metal(S/N) structures, in
the diffusive regime, analysing both weak and strong proximity effects. We show
that in the case of a weak proximity effect there are two peaks in the
dependence of on temperature. One of them (known from previous
studies) corresponds to a temperature of order of the Thouless energy
(), and another, newly predicted maximum, occurs at a
temperature where the energy gap in the superconductor is
of order . In the limit the temperature is
determined by ( is the phase breaking length),
and not . We have also calculated the voltage dependence for a S/F structure (F is a ferromagnet) and predict non-monotonic
behaviour at voltages of order the Zeeman splitting.Comment: 6 figures. Submitted to PRB Rapid com
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