7,958 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
Primeval symmetries
A detailed examination of the Killing equations in Robertson-Walker
coordinates shows how the addition of matter and/or radiation to a de Sitter
Universe breaks the symmetry generated by four of its Killing fields. The
product U = (a^2)(dH/dt) of the squared scale parameter by the time-derivative
of the Hubble function encapsulates the relationship between the two cases: the
symmetry is maximal when U is a constant, and reduces to the six-parameter
symmetry of a generic Friedmann-Robertson-Walker model when it is not. As the
fields physical interpretation is not clear in these coordinates, comparison is
made with the Killing fields in static coordinates, whose interpretation is
made clearer by their direct relationship to the Poincare group generators via
Wigner-Inonu contractions.Comment: 16 pages, 2 tables; published versio
Determination of spin polarization in InAs/GaAs self-assembled quantum dots
The spin polarization of electrons trapped in InAs self-assembled quantum dot
ensembles is investigated. A statistical approach for the population of the
spin levels allows one to infer the spin polarization from the measure values
of the addition energies. From the magneto-capacitance spectroscopy data, the
authors found a fully polarized ensemble of electronic spins above 10 T when
and at 2.8 K. Finally, by including the g-tensor
anisotropy the angular dependence of spin polarization with the magnetic field
orientation and strength could be determined.Comment: 3 pages, 2 figures, Accepted Appl. Phys. Let
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