scholarly journals Non-Riemmanian geometry, force-free magnetospheres and the generalized Grad-Shafranov equation

2019 ◽  
Vol 16 (01) ◽  
pp. 1950013 ◽  
Author(s):  
Diego Julio Cirilo-Lombardo
Keyword(s):  
Generalized Equation ◽  
Excess Energy ◽  
Quantum Field ◽  
Axially Symmetric ◽  
Complex Character ◽  
Function Solution ◽  
Electron Positron ◽  
Shafranov Equation ◽  
Symmetric Version ◽  
Electron Positron Pair

The magnetosphere structure of a magnetar is considered in the context of a theory of gravity with dynamical torsion field beyond the standard General Relativity (GR). To this end, the axially symmetric version of the Grad-Shafranov equation (GSE) is obtained in this theoretical framework. The resulting GSE solution in the case of the magnetosphere corresponds to a stream function containing also a pseudoscalar part. This function solution under axisymmetry presents a complex character that (as in the quantum field theoretical case) could be associated with an axidilaton field. Magnetar–pulsar mechanism is suggested and the conjecture about the origin of the excess energy due the GSE describing the magnetosphere dynamics is claimed. We also show that two main parameters of the electrodynamic processes (as described in GR framework by Goldreich and Julian (GJ) [Astrophys. J. 157 (1969) 869]) are modified but the electron-positron pair rate [Formula: see text] remains invariant. The possible application of our generalized equation (defined in a non-Riemannian geometry) to astrophysical scenarios involving emission of energy by gravitational waves, as described in the context of GR in [S. Capozziello, M. De Laurentis, I. De Martino, M. Formisano and D. Vernieri, Astrophys. Space Sci. 333 (2011) 29–35], is briefly discussed.

Beyond general relativity models, magnetosphere structure and dark matter stars

2019 ◽  
Vol 16 (04) ◽  
pp. 1950064 ◽  
Author(s):  
D. J. Cirilo-Lombardo ◽  
F. O. Minotti
Keyword(s):  
General Relativity ◽  
Compact Object ◽  
High Energy ◽  
Compact Objects ◽  
Axially Symmetric ◽  
Spherically Symmetric Solution ◽  
Axion Field ◽  
Shafranov Equation ◽  
Symmetric Version ◽  
Energy Processes

The magnetosphere structure of compact objects is considered in the context of a theory of gravity with dynamical torsion field beyond standard General Relativity (GR). To this end, a new spherically symmetric solution is obtained in this theoretical framework, physically representing a compact object of pseudoscalar fields (for example, axion field). The axially symmetric version of the Grad–Shafranov equation (GSE) is also derived in this context, and used to describe the magnetosphere dynamics of the obtained “axion star”. The interplay between high-energy processes and the seed magnetic field with respect to the global structure of the magnetosphere is briefly discussed.

Vacuum polarization and particle creation in the presence of a potential step

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641031 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Potential ◽  
Canonical Quantization ◽  
Particle Creation ◽  
Pair Creation ◽  
Dirac Field ◽  
Potential Step ◽  
Electron Positron ◽  
Physical Impact ◽  
Particle Interpretation ◽  
Electron Positron Pair

We consider QED with strong external backgrounds that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x-electric potential steps for charged particles. They can create particles from the vacuum, the Klein paradox being closely related to this process. We describe a canonical quantization of the Dirac field with x-electric potential step in terms of adequate in- and out-creation and annihilation operators that allow one to have consistent particle interpretation of the physical system under consideration and develop a nonperturbative (in the external field) technics to calculate scattering, reflection, and electron-positron pair creation. We resume the physical impact of this development.

Electron-Positron Pair Production in an Elliptic Polarized Time Varying Field

2012 ◽  
Vol 29 (2) ◽  
pp. 021102 ◽  
Author(s):  
Bai-Song Xie ◽  
Mohamedsedik Melike ◽  
Dulat Sayipjamal
Keyword(s):  
Pair Production ◽  
Time Varying ◽  
Electron Positron ◽  
Electron Positron Pair

scholarly journals Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special?

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
J. J. Geng ◽  
Y. F. Huang
Keyword(s):  
Black Holes ◽  
Numerical Method ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Shock Model ◽  
Reverse Shock ◽  
X Ray ◽  
Electron Positron ◽  
Forward Shock ◽  
Electron Positron Pair

The detection of optical rebrightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamics of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical rebrightenings would be caused by the fall-back accretion of black holes, while the shallow optical rebrightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines.

scholarly journals Derivative corrections to the Heisenberg-Euler effective action

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Felix Karbstein
Keyword(s):  
Electric Fields ◽  
Effective Action ◽  
Vacuum Polarization ◽  
Strong Field ◽  
Background Field ◽  
Polarization Tensor ◽  
Quantum Vacuum ◽  
Electron Positron ◽  
Vacuum Polarization Tensor ◽  
Electron Positron Pair

Abstract We show that the leading derivative corrections to the Heisenberg-Euler effective action can be determined efficiently from the vacuum polarization tensor evaluated in a homogeneous constant background field. After deriving the explicit parameter-integral representation for the leading derivative corrections in generic electromagnetic fields at one loop, we specialize to the cases of magnetic- and electric-like field configurations characterized by the vanishing of one of the secular invariants of the electromagnetic field. In these cases, closed-form results and the associated all-orders weak- and strong-field expansions can be worked out. One immediate application is the leading derivative correction to the renowned Schwinger-formula describing the decay of the quantum vacuum via electron-positron pair production in slowly-varying electric fields.

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