133 research outputs found
Pair Creation of Massless Fermions in Electric Flux Tube
Using chiral anomaly, we discuss the pair creation of massless fermions in an
electric flux tube under homogeneous magnetic field
parallel to . The tube is axial symmetric and infinitely long in
longitudinal direction. In the limit , we can analytically obtain the
spatial and temporal behaviors of the electric field and azimuthal magnetic
field generated by the produced fermions. We find that the life time of
the electric field is shorter as the width of the tube is narrower. Applying it
to the glasma in high-energy heavy-ion collisions, we find that color electric
field decays fast such as with saturation momentum .Comment: 6 pages, 4 figure
Acceleration and vacuum temperature
The quantum fluctuations of an "accelerated" vacuum state, that is vacuum
fluctuations in the presence of a constant electromagnetic field, can be
described by the temperature \TEH. Considering \TEH for the gyromagnetic
factor we show that \TEH(g=1)=\THU, where \THU is the Unruh
temperature experienced by an accelerated observer. We conjecture that both
particle production and nonlinear field effects inherent in the Unruh
accelerated observer case are described by the case QED of strong fields.
We present rates of particle production for and show that the case
is experimentally distinguishable from . Therefore, either
accelerated observers are distinguishable from accelerated vacuum or there is
unexpected modification of the theoretical framework.Comment: 4 pages, 1 figure; expanded discussion of experimental observables,
added references, version appearing in Phys Rev
Non-Linear Compton Scattering of Ultrashort and Ultraintense Laser Pulses
The scattering of temporally shaped intense laser pulses off electrons is
discussed by means of manifestly covariant quantum electrodynamics. We employ a
framework based on Volkov states with a time dependent laser envelope in
light-cone coordinates within the Furry picture. An expression for the cross
section is constructed, which is independent of the considered pulse shape and
pulse length. A broad distribution of scatted photons with a rich pattern of
subpeaks like that obtained in Thomson scattering is found. These broad peaks
may overlap at sufficiently high laser intensity, rendering inappropriate the
notion of individual harmonics. The limit of monochromatic plane waves as well
as the classical limit of Thomson scattering are discussed. As a main result, a
scaling law is presented connecting the Thomson limit with the general result
for arbitrary kinematics. In the overlapping regions of the spectral density,
the classical and quantum calculations give different results, even in the
Thomson limit. Thus, a phase space region is identified where the differential
photon distribution is strongly modified by quantum effects.Comment: 31 pages, 10 figure
Schwinger Pair Production at Finite Temperature in Scalar QED
In scalar QED we study the Schwinger pair production from an initial ensemble
of charged bosons when an electric field is turned on for a finite period
together with or without a constant magnetic field. The scalar QED Hamiltonian
depends on time through the electric field, which causes the initial ensemble
of bosons to evolve out of equilibrium. Using the Liouville-von Neumann method
for the density operator and quantum states for each momentum mode, we
calculate the Schwinger pair-production rate at finite temperature, which is
the pair-production rate from the vacuum times a thermal factor of the
Bose-Einstein distribution.Comment: RevTex 10 pages, no figure; replaced by the version accepted in Phys.
Rev. D; references correcte
Enhanced subthreshold electron-positron production in short laser pulses
The emission of electron-positron pairs off a probe photon propagating
through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field is
analyzed.
A significant increase of the total cross section of pair production in the
subthreshold region is found for decreasing laser pulse duration even in case
of moderate laser pulse intensities.Comment: 4 pages, 2 figure
Worldline approach to helicity flip in plane waves
We apply worldline methods to the study of vacuum polarisation effects in
plane wave backgrounds, in both scalar and spinor QED. We calculate
helicity-flip probabilities to one loop order and treated exactly in the
background field, and provide a toolkit of methods for use in investigations of
higher-order processes. We also discuss the connections between the worldline,
S-matrix, and lightfront approaches to vacuum polarisation effects.Comment: 11 pages, 1 figur
Dynamics of the Chiral Magnetic Effect in a weak magnetic field
We investigate the real-time dynamics of the chiral magnetic effect in
quantum electrodynamics (QED) and quantum chromodynamics (QCD). We consider a
field configuration of parallel (chromo)electric and (chromo)magnetic fields
with a weak perpendicular electromagnetic magnetic field. The chiral magnetic
effect induces an electromagnetic current along this perpendicular magnetic
field, which we will compute using linear response theory. We discuss specific
results for a homogeneous sudden switch-on and a pulsed (chromo)electric field
in a static and homogeneous (chromo)magnetic field. Our methodology can be
easily extended to more general situations. The results are useful for
investigating the chiral magnetic effect with heavy ion collisions and with
lasers that create strong electromagnetic fields. As a side result we obtain
the rate of chirality production for massive fermions in parallel electric and
magnetic fields that are static and homogeneous.Comment: 13 pages, 7 figures, revte
Effective Action of QED in Electric Field Backgrounds II: Spatially Localized Fields
We find the Bogoliubov coefficient from the tunneling boundary condition on a
charged particle coupled to a static electric field and,
using the regularization scheme in Phys. Rev. D 78, 105013 (2008), obtain the
exact one-loop effective action in scalar and spinor QED. It is shown that the
effective action satisfies the general relation between the vacuum persistence
and the mean number of produced pairs. We advance an approximation method for
general electric fields and show the duality between the space-dependent and
time-dependent electric fields of the same form at the leading order of the
effective actions.Comment: RevTex 7 pages, no figure; extension of arXiv:0807.2696 to
space-dependent electric fields; new section added on approximate effective
actions in general electric fields and conclusion shortened; references
added; replaced by the version to be published in Phys. Rev.
Vacuum Decay Time in Strong External Fields
We consider dynamics of vacuum decay and particle production in the context
of short pulse laser experiments. We identify and evaluate the invariant
"materialization time," , the timescale for the conversion of an
electromagnetic field energy into particles, and we compare to the laser
related time scales.Comment: 4 pages, 2 figures; improved representation of eq. 12, improved
figures, added references, improved introductory material, and corrected
typo
Quantum effects with an X-ray free electron laser
A quantum kinetic equation coupled with Maxwell's equation is used to
estimate the laser power required at an XFEL facility to expose intrinsically
quantum effects in the process of QED vacuum decay via spontaneous pair
production. A 9 TW-peak XFEL laser with photon energy 8.3 keV could be
sufficient to initiate particle accumulation and the consequent formation of a
plasma of spontaneously produced pairs. The evolution of the particle number in
the plasma will exhibit non-Markovian aspects of the strong-field pair
production process and the plasma's internal currents will generate an electric
field whose interference with that of the laser leads to plasma oscillations.Comment: 4 pages, LaTeX2
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