1,047,843 research outputs found
Pair creation by a photon in a strong magnetic field
The process of pair creation by a photon in a strong magnetic field is
investigated basing on the polarization operator in the field. The total
probability of the process is found in a relatively simple form. The
probability exhibits a "saw-tooth" pattern because of divergences arising when
the electron and positron are created at threshold of the Landau energy levels.
The pattern will be washed out at averaging over any smooth photon energy
distribution. The new results are obtained in the scope of the quasiclassical
approach: 1) in the case when the magnetic field is the
critical field) the new formulation extends the photon energy interval to the
case when the created particles are not ultrarelativistic; 2) the correction to
the standard quasiclassical approximation is found showing the range of
applicability of the approach at high photon energy as well. The very important
conclusion is that for both cases and the results of
the quasiclassical calculation are very close to averaged probabilities of
exact theory in a very wide range of photon energies. The quasiclassical
approximation is valid also for the energy distribution if the electron and
positron are created on enough high levels.Comment: 21 pages, 6 figure
Mass dependence of nuclear shadowing at small Bjorken-x from diffractive scattering
We calculate the nuclear shadowing ratio for a wide range of nuclei at small
Bjorken-x in the framework of Gribov theory. The coherent contribution to the
(virtual) photon-nucleon cross section is obtained in terms of the diffractive
dissociation cross section. Information on diffraction from FNAL and HERA is
used. Our results are compared to available experimental data from the NMC and
E665 experiments at x ~ 10^{-4}.Comment: To be published in Phys. Rev.
Dynamics of two-component electromagnetic and acoustic extremely short pulses
The distinctive features of passing the two-component extremely short pulses
through the nonlinear media are discussed. The equations considered describe
the propagation in the two-level anisotropic medium of the electromagnetic
pulses consisting of ordinary and extraordinary components and an evolution of
the transverse-longitudinal acoustic pulses in a crystal containing the
paramagnetic impurities with effective spin S=1/2. The solutions decreasing
exponentially and algebraically are studied.Comment: LaTeX, 11 pages, 6 figure
Delbr\"uck scattering in combined Coulomb and laser fields
We study Delbr\"uck scattering in a Coulomb field in the presence of a laser
field. The amplitudes are calculated in the Born approximation with respect to
the Coulomb field and exactly in the parameters of the laser field having
arbitrary strength, spectral content and polarization. The case of high energy
initial photon energy is investigated in detail for a monochromatic circularly
polarized laser field. It is shown that the angular distribution of the process
substantially differs from that for Delbr\"uck scattering in a pure Coulomb
field. The value of the cross section under discussion may exceed the latter at
realistic laser parameters that essentially simplify the possibility of the
experimental observation of the phenomenon. The effect of high order terms in
the quantum intensity parameter of the laser field is found to be very
important already at relatively small .Comment: 21 pages, 4 figure
Search for the scalar a_0 and f_0 mesons in the \phi radiative decays
The potentialities of the production of the and mesons in the
radiative decays are considered based on a new two-channel analysis of
the scattering in a energy region near 1 GeV. We predict
that is a great value for the
decay forbidden by the Okubo-Zweig-Iizuka rule. We discuss the four-quark,
-molecule and two-quark scenarios for the and mesons. It
is presented arguments that the -colliders and especially the
factories give the possibility to choose a single one out of them.Comment: Talk given at HADRON-9
Two new type surface polaritons excited into nanoholes in metal films
First, we argue that the smooth metal-air interface should be regarded as a
distinct dielectric medium, the skin of the metal. The existence of this metal
skin leads to theoretical explanation of experimental data on the excitation of
electromagnetic surface shape resonances in lamellar metallic gratings by light
in the visible to near-infrared range. Surface polaritons have been observed in
reflection modes on metallized gratings where the electric field is highly
localized inside the grooves (around 300-1000 times larger than intensity of
incoming optical light). Here we present quantized Maxwell's equations for
electromagnetic field in an isotropic homogeneous medium, allowing us to solve
the absorption anomaly property of these metal films. The results imply the
existence of light boson particles with spin one and effective mass . We also show the presence of two new type surface
polaritons into nanoholes in metal films.Comment: 10 pages. Accepted on November 30, 2009 in Progress in Physic
Intrinsic tunneling or Joule heating?
It is shown that the `tunnelling spectra' reported by Yurgens et al. could be
reproduced qualitatively and quantitatively using the experimental out-of-plane
normal state resistance R(T) and assuming that the heating of the mesa, caused
by the Joule dissipation, is the only reason for effects observed at high bias.Comment: Comment on 'Intrinsic Tunneling Spectra of Bi2201 by A.Yurgens et
al., Phys. Rev. Lett. 90, 147005, (2003); typo correcte
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