6,135 research outputs found
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
Spin-polarized Josephson and quasiparticle currents in superconducting spin-filter tunnel junctions
We present a theoretical study of the effect of spin-filtering on the
Josephson and dissipative quasiparticle currents in a superconducting tunnel
junction. By combining the quasiclassical Green's functions and the tunneling
Hamiltonian method we describe the transport properties of a generic junction
consisting of two superconducting leads with an effective exchange field h
separated by a spin-filter insulating barrier. We show that besides the
tunneling of Cooper pairs with total spin-projection Sz = 0 there is another
contribution to the Josephson current due to equal-spin Cooper pairs. The
latter is finite and not affected by the spin-filter effect provided that the
fields h and the magnetization of the barrier are non-collinear . We also
determine the quasiparticle current for a symmetric junction and show that the
differential conductance may exhibit peaks at different values of the voltage
depending on the polarization of the spin-filter, and the relative angle
between the exchange fields and the magnetization of the barrier. Our findings
provide a plausible explanation for existing experiments on Josephson junctions
with magnetic barriers, predict new effects and show how spin-polarized
supercurrents in hybrid structures can be created.Comment: 5 pages; 3 figure
Characterizing asymptotically anti-de Sitter black holes with abundant stable gauge field hair
In the light of the "no-hair" conjecture, we revisit stable black holes in
su(N) Einstein-Yang-Mills theory with a negative cosmological constant. These
black holes are endowed with copious amounts of gauge field hair, and we
address the question of whether these black holes can be uniquely characterized
by their mass and a set of global non-Abelian charges defined far from the
black hole. For the su(3) case, we present numerical evidence that stable black
hole configurations are fixed by their mass and two non-Abelian charges. For
general N, we argue that the mass and N-1 non-Abelian charges are sufficient to
characterize large stable black holes, in keeping with the spirit of the
"no-hair" conjecture, at least in the limit of very large magnitude
cosmological constant and for a subspace containing stable black holes (and
possibly some unstable ones as well).Comment: 33 pages, 13 figures, minor change
Degenerate Odd Poisson Bracket on Grassmann Variables
A linear degenerate odd Poisson bracket (antibracket) realized solely on
Grassmann variables is presented. It is revealed that this bracket has at once
three nilpotent -like differential operators of the first, the second
and the third orders with respect to the Grassmann derivatives. It is shown
that these -like operators together with the Grassmann-odd nilpotent
Casimir function of this bracket form a finite-dimensional Lie superalgebra.Comment: 5 pages, LATEX. Corrections of misprints. The relation (23) is adde
Spin-Orbit Interactions in Bilayer Exciton-Condensate Ferromagnets
Bilayer electron-hole systems with unequal electron and hole densities are
expected to have exciton condensate ground states with spontaneous
spin-polarization in both conduction and valence bands. In the absence of
spin-orbit and electron-hole exchange interactions there is no coupling between
the spin-orientations in the two quantum wells. In this article we show that
Rashba spin-orbit interactions lead to unconventional magnetic anisotropies,
whose strength we estimate, and to ordered states with unusual quasiparticle
spectra.Comment: 36 pages, 12 figure
On the existence of dyons and dyonic black holes in Einstein-Yang-Mills theory
We study dyonic soliton and black hole solutions of the
Einstein-Yang-Mills equations in asymptotically anti-de Sitter space. We prove
the existence of non-trivial dyonic soliton and black hole solutions in a
neighbourhood of the trivial solution. For these solutions the magnetic gauge
field function has no zeros and we conjecture that at least some of these
non-trivial solutions will be stable. The global existence proof uses local
existence results and a non-linear perturbation argument based on the (Banach
space) implicit function theorem.Comment: 23 pages, 2 figures. Minor revisions; references adde
Scalar Mesons in a Chiral Quark Model with Glueball
Ground-state scalar isoscalar mesons and a scalar glueball are described in a
U(3)xU(3) chiral quark model of the Nambu--Jona-Lasinio (NJL) type with 't
Hooft interaction. The latter interaction produces singlet-octet mixing in the
scalar and pseudoscalar sectors. The glueball is introduced into the effective
meson Lagrangian as a dilaton on the base of scale invariance. The mixing of
the glueball with scalar isoscalar quarkonia and amplitudes of their decays
into two pseudoscalar mesons are shown to be proportional to current quark
masses, vanishing in the chiral limit. Mass spectra of the scalar mesons and
the glueball and their main modes of strong decay are described.Comment: 10 pages, LaTeX text, requires svjour.cls and svepj.cl
Studies of the expression of subunits α2 and β1 of Na<sup>+</sup>/K<sup>+</sup>-ATPase, α1S (L-type) Ca<sup>2+</sup>-channel, and SERCA 1/2/3 of Ca<sup>2+</sup>-ATPase of phasic and postural rat muscles in a model of hypogravity using the method of fluorescent microscopy
© 2016, Pleiades Publishing, Ltd.Using fluorescent microscopy, we found decreased expression of the β1 subunit of Na+/K+-ATPase and subunits of Ca2+-ATPase, increased expression of the α1S subunit of the L-type Ca2+-channel, and no changes in the expression of the α2 subunit of Na+/K+-ATPase in rat postural muscle under the conditions of modeled hypogravity. In the phasic muscle, we observed decreased expression of the β1 subunit, which was similar to that found in the postural muscle, whereas the other studied parameters remained without alterations. However, a decrease in the fluorescence intensity of the β1 subunit was insignificant due to a high variability of data. Thus, hypogravity negatively influenced primarily those skeletal muscles that are responsible for static load
- …