1,191 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
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
Coulomb effects in the spin-dependent contribution to the intra-beam scattering rate
Coulomb effects in the intra-beam scattering are taken into account in a way
providing correct description of the spin-dependent contribution to the beam
loss rate. It allows one to calculate this rate for polarized beams
at arbitrarily small values of the ratio ,
characterizing relative change of the electron energy in the laboratory system
during scattering event.Comment: 8 pages, 2 figure
Laser-dressed vacuum polarization in a Coulomb field
We investigate quantum electrodynamic effects under the influence of an
external, time-dependent electromagnetic field, which mediates dynamic
modifications of the radiative corrections. Specifically, we consider the
quantum electrodynamic vacuum-polarization tensor under the influence of two
external background fields: a strong laser field and a nuclear Coulomb field.
We calculate the charge and current densities induced by a nuclear Coulomb
field in the presence of a laser field. We find the corresponding induced
scalar and vector potentials. The induced potential, in first-order
perturbation theory, leads to a correction to atomic energy levels. The
external laser field breaks the rotational symmetry of the system.
Consequently, the induced charge density is not spherically symmetric, and the
energy correction therefore leads to a "polarized Lamb shift." In particular,
the laser generates an additional potential with a quadrupole moment. The
corresponding laser-dressed vacuum-polarization potential behaves like 1/r**3
at large distances, unlike the Uehling potential that vanishes exponentially
for large r. Our investigation might be useful for other situations where
quantum field theoretic phenomena are subjected to external fields of a rather
involved structure.Comment: 13 pages, RevTe
Photon splitting in a laser field
Photon splitting due to vacuum polarization in a laser field is considered.
Using an operator technique, we derive the amplitudes for arbitrary strength,
spectral content and polarization of the laser field. The case of a
monochromatic circularly polarized laser field is studied in detail and the
amplitudes are obtained as three-fold integrals. The asymptotic behavior of the
amplitudes for various limits of interest are investigated also in the case of
a linearly polarized laser field. Using the obtained results, the possibility
of experimental observation of the process is discussed.Comment: 31 pages, 4 figure
Radiation Emission by Extreme Relativistic Electrons and Pair Production by Hard Photons in a Strong Plasma Wakefield
Radiation spectrum of extreme relativistic electrons and a probability of
electron-positron pair production by energetic photons in a strong plasma
wakefield are derived in the framework of a semiclassical approach. It is shown
that that the radiation losses of the relativistic electron in the plasma
wakefield scale as in the quantum limit when the
energy of the radiated photon becomes close to the electron energy, . The quantum effects will play a key role in future plasma-based accelerators
operating at ultrahigh energy of the electrons.Comment: 10 pages, 2 figure
Photon Splitting in a Very Strong Magnetic Field
Photon splitting in a very strong magnetic field is analyzed for energy
. The amplitude obtained on the base of operator-diagram technique
is used. It is shown that in a magnetic field much higher than critical one the
splitting amplitude is independent on the field. Our calculation is in a good
agreement with previous results of Adler and in a strong contradiction with
recent paper of Mentzel et al.Comment: 5 pages,Revtex , 4 figure
"Planck-scale physics" of vacuum in a strong magnetic field
It is widely believed that Lorentz symmetry of physical vacuum is broken near
the Planck scale. Here we show that recently demonstrated "hyperbolic
metamaterial" behaviour of vacuum in a strong magnetic field provides us with
an interesting analogy of the Planck-scale physics. As demonstrated by
Chernodub, strong magnetic field forces vacuum to develop real condensates of
electrically charged \rho mesons, which form an anisotropic inhomogeneous
superconducting state similar to Abrikosov vortex lattice. As far as
electromagnetic field behaviour is concerned, this hyperbolic metamaterial
state of vacuum exhibits effective 3D Lorentz symmetry, which is broken at
small scale (large momenta) due to spatial dispersion. Thus, an effective
Lorentz symmetry-violating "Planck scale" may be introduced. Near the critical
magnetic field this effective "Planck scale" is much larger than the
metamaterial periodicity defined by the \rho meson lattice. Similar to regular
hyperbolic metamaterials, spatial dispersion of vacuum in a strong magnetic
field leads to appearance of the "additional wave", which manifests itself as a
"heavy" extraordinary photon with an effective mass ~2GeV.Comment: 14 pages, 2 figures, this version is accepted for publication in
Phys.Rev.
Non-perturbative vacuum-polarization effects in proton-laser collisions
In the collision of a high-energy proton beam and a strong laser field,
merging of the laser photons can occur due to the polarization of vacuum. The
probability of photon merging is calculated by accounting exactly for the laser
field and presents a highly non-perturbative dependence on the laser intensity
and frequency. It is shown that the non-perturbative vacuum-polarization
effects can be experimentally measured by combining the next-generation of
table-top petawatt lasers with presently available proton accelerators.Comment: 5 pages, 2 figure
Nonlinear double Compton scattering in the full quantum regime
A detailed analysis of the process of two photon emission by an electron
scattered from a high-intensity laser pulse is presented. The calculations are
performed in the framework of strong-field QED and include exactly the presence
of the laser field, described as a plane wave. We investigate the full quantum
regime of interaction, where photon recoil plays an essential role in the
emission process, and substantially alters the emitted photon spectra as
compared to those in previously-studied regimes. We provide a semiclassical
explanation for such differences, based on the possibility of assigning a
trajectory to the electron in the laser field before and after each quantum
photon emission. Our numerical results indicate the feasibility of
investigating experimentally the full quantum regime of nonlinear double
Compton scattering with already available plasma-based electron accelerator and
laser technology.Comment: 5 pages, 3 figure
- …