1,985 research outputs found
Improved local-constant-field approximation for strong-field QED codes
The local-constant-field approximation (LCFA) is an essential theoretical
tool for investigating strong-field QED phenomena in background electromagnetic
fields with complex spacetime structure. In our previous work
[Phys.~Rev.~A~\textbf{98}, 012134 (2018)] we have analyzed the shortcomings of
the LCFA in nonlinear Compton scattering at low emitted photon energies for the
case of a background plane-wave field. Here, we generalize that analysis to
background fields, which can feature a virtually arbitrary spacetime structure.
In addition, we provide an explicit and simple implementation of an improved
expression of the nonlinear Compton scattering differential probability that
solves the main shortcomings of the standard LCFA in the infrared region, and
is suitable for background electromagnetic fields with arbitrary spacetime
structure such as those occurring in particle-in-cell simulations. Finally, we
carry out a systematic procedure to calculate the probability of nonlinear
Compton scattering per unit of emitted photon light-cone energy and of
nonlinear Breit-Wheeler pair production per unit of produced positron
light-cone energy beyond the LCFA in a plane-wave background field, which
allows us to identify the limits of validity of this approximation
quantitatively.Comment: 15 pages, 3 figure
Implementing nonlinear Compton scattering beyond the local constant field approximation
In the calculation of probabilities of physical processes occurring in a
background classical field, the local constant field approximation (LCFA)
relies on the possibility of neglecting the space-time variation of the
external field within the region of formation of the process. This
approximation is widely employed in strong-field QED as it allows to evaluate
probabilities of processes occurring in arbitrary electromagnetic fields
starting from the corresponding quantities computed in a constant
electromagnetic field. Here, we demonstrate in the case of nonlinear single
Compton scattering that the LCFA is quantitatively and qualitatively
insufficient for describing the low-energy part of the emitted photon
probability. In addition, we provide a simple recipe to implement an improved
expression of the photon emission probability beyond the LCFA in numerical
codes, which are an essential tool to interpret present and upcoming
experiments in strong-field QED.Comment: 12 pages, 3 figur
Pair production in a strong slowly varying magnetic field: the effect of a background gravitational field
The production probability of an pair in the presence of a strong,
uniform and slowly varying magnetic field is calculated by taking into account
the presence of a background gravitational field. The curvature of the
spacetime metric induced by the gravitational field not only changes the
transition probabilities calculated in the Minkowski spacetime but also primes
transitions that are strictly forbidden in absence of the gravitational field.Comment: 56 pages, no figure
One-loop vertex correction in a plane wave
We compute the general expression of the one-loop vertex correction in an
arbitrary plane-wave background field for the case of two on-shell external
electrons and an off-shell external photon. The properties of the vertex
corrections under gauge transformations of the plane-wave background field and
of the radiation field are studied. Concerning the divergences of the vertex
correction, the infrared one is cured by assigning a finite mass to the photon,
whereas the ultraviolet one is shown to be renormalized exactly as in vacuum.
Finally, the corresponding expression of the vertex correction within the
locally-constant crossed field is also derived and the high-field asymptotic is
shown to scale according to the Ritus-Narozhny conjecture.Comment: 42 pages, 5 figure
Immersive Virtual Reality for Cultural Heritage Exploration
Virtual Reality can provide an immersive experience that allows cultural heritage to be experienced in a more realistic and immersive way than traditional showcasing techniques. The objective of this paper is to provide a software pipeline that can be adopted for the realization of immersive experiences in cultural heritage sites. This work has been realized within the 3DLab-Sicilia project, which includes the realization of immersive virtual tours of UNESCO World Heritage sites located in the Sicily area (Italy)
Troponina e infarto periprocedurale: filo di Arianna o folle volo di Icaro?
Percutaneous coronary interventions cause frequently an increase in myocardial necrosis markers. Is troponin elevation after percutaneous coronary intervention a predictor of events at follow-up or a consequence of the procedure with no cause-effect relationship with prognosis? The debate is still ope
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