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      Falsifying cosmological models based on a non-linear electrodynamics

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          Abstract

          Recently, the nonlinear electrodynamics (NED) has been gaining attention to generate primordial magnetic fields in the Universe and also to resolve singularity problems. Moreover, recent works have shown the crucial role of the NED on the inflation. This paper provides a new approach based on a new model of NED as a source of gravitation to remove the cosmic singularity at the big bang and explain the cosmic acceleration during the inflation era without initial singularity on the background of stochastic magnetic field. We explore whether a NED field can be the origin of the cosmic acceleration. Also, we found a realization of a cyclic Universe, free of initial singularity, due the model for the NED energy density we propose. We find explicit relations for \(H(z)\) by direct integration of the equations of motion of the proposed model. We perform MCMC likelihood exploration of these relations using Observational Hubble data to find the mean values for the NED parameters. We compute the deceleration parameter \(q(z)\) in the range \(0<z<2\) from the best fit values of the parameters and find \(q(z)\rightarrow 1/2\) at \(z\rightarrow \infty\). Moreover, the Universe passes of a decelerated phase to an accelerated stage at redshift \(\sim 0.5\). The result is that the are not statistical differences with the usual model during the radiation epoch which holds for \(\alpha=0\). However, taking \(\alpha\) slightly different from zero, we find that the NED with dust matter (\(w_{m}=0\)) is able to drive the late-time cosmic acceleration of the standard cosmological model.

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          Cosmological Magnetic Fields: Their Generation, Evolution and Observation

          We review the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding Universe filled with the cosmic plasma and provide a critical review of the literature on the subject. We put special emphasis on the prospects for observational tests of the proposed cosmological magnetogenesis scenarios using radio and gamma-ray astronomy and ultra high energy cosmic rays. We argue that primordial magnetic fields are observationally testable. They lead to magnetic fields in the intergalactic medium with magnetic field strength and correlation length in a well defined range. We also state the unsolved questions in this fascinating open problem of cosmology and propose future observations to address them.
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            Nonlinear electrodynamics and FRW cosmology

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              Inflation-Produced Magnetic Fields in R^n F^2 and I F^2 models

              We re-analyze the production of seed magnetic fields during Inflation in (R/m^2)^n F_{\mu \nu}F^{\mu \nu} and I F_{\mu \nu}F^{\mu \nu} models, where n is a positive integer, R the Ricci scalar, m a mass parameter, and I \propto \eta^\alpha a power-law function of the conformal time \eta, with \alpha a positive real number. If m is the electron mass, the produced fields are uninterestingly small for all n. Taking m as a free parameter we find that, for n \geq 2, the produced magnetic fields can be sufficiently strong in order to seed dynamo mechanism and then to explain galactic magnetism. For \alpha \gtrsim 2, there is always a window in the parameters defining Inflation such that the generated magnetic fields are astrophysically interesting. Moreover, if Inflation is (almost) de Sitter and the produced fields almost scale-invariant (\alpha \simeq 4), their intensity can be strong enough to directly explain the presence of microgauss galactic magnetic fields.
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                Author and article information

                Journal
                27 September 2017
                Article
                1709.09794
                04fcfcbd-a8af-4a13-a1ac-a997a05246fd

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

                History
                Custom metadata
                36 pages, 14 figures
                gr-qc astro-ph.CO hep-th

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