5,164 research outputs found
Constraining Born-Infeld-like Nonlinear Electrodynamics Using Hydrogen's Ionization Energy
In this work, the hydrogen's ionization energy was used to constrain the free
parameter of three Born-Infeld-like electrodynamics namely Born-Infeld
itself, Logarithmic electrodynamics and Exponential electrodynamics. An
analytical methodology capable of calculating the hydrogen ground state energy
level correction for a generic nonlinear electrodynamics was developed. Using
the experimental uncertainty in the ground state energy of the hydrogen atom,
the bound , where , and
for the Born-Infeld, Logarithmic and Exponential electrodynamics
respectively, was established. In the particular case of Born-Infeld
electrodynamics, the constraint found for was compared with other
constraints present in the literature.Comment: 9 pages, 1 figure, references adde
Thermodynamics of a Photon Gas in Nonlinear Electrodynamics
In this paper we analyze the thermodynamic properties of a photon gas under
the influence of a background electromagnetic field in the context of any
nonlinear electrodynamics. Neglecting the self-interaction of photons, we
obtain a general expression for the grand canonical potential. Particularizing
for the case when the background field is uniform, we determine the pressure
and the energy density for the photon gas. Although the pressure and the energy
density change when compared with the standard case, the relationship between
them remains unaltered, namely . Finally, we apply the developed
formulation to the cases of Heisenberg-Euler and Born-Infeld nonlinear
electrodynamics. For the Heisenberg-Euler case, we show that our formalism
recover the results obtained with the -loop thermal effective action
approach.Comment: 7 pages, 1 figures. A new section about H.E. effective action added
in this version. Accepted PL
Four-dimensional topological Einstein-Maxwell gravity
The complete on-shell action of topological Einstein-Maxwell gravity in
four-dimensions is presented. It is shown explicitly how this theory for SU(2)
holonomy manifolds arises from four-dimensional Euclidean N=2 supergravity. The
twisted local BRST symmetries and twisted local Lorentz symmetries are given
and the action and stress tensor are shown to be BRST-exact. A set of
BRST-invariant topological operators is given. The vector and antisymmetric
tensor twisted supersymmetries and their algebra are also found.Comment: Published version. Expanded discussion of new results in the
introduction and some clarifying remarks added in later sections. 22 pages,
uses phyzz
Causal Structure and Birefringence in Nonlinear Electrodynamics
We investigate the causal structure of general nonlinear electrodynamics and
determine which Lagrangians generate an effective metric conformal to
Minkowski. We also proof that there is only one analytic nonlinear
electrodynamics presenting no birefringence.Comment: 11 pages, no figure
Comportamento produtivo de caprinos anglo-nubiano no estado do Piaui.
bitstream/item/97227/1/PAND320001.pd
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