Departamento de Física
URI permanente para esta comunidadhttps://hdl.handle.net/10953/33
En esta Comunidad se recogen los documentos generados por el Departamento de Física y que cumplen los requisitos de Copyright para su difusión en acceso abierto.
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Examinando Departamento de Física por Autor "Garrido Pestaña, J.L."
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Ítem Dark Future for Dark Matter(SCIRP (Scientific Research Publishing Inc.), 2020-01) Eckhardt, D.H.; Garrido Pestaña, J.L.The prevailing cosmological constant and cold dark matter (LCDM) cosmic concordance model accounts for the radial expansion of the universe after the Big Bang. The model appears to be authoritative because it is based on the Einstein gravitational field equation. However, a thorough scrutiny of the underlying theory calls into question the suitability of the field equation, which states that the Einstein tensor is a constant multiple of the stress-energy tensor when they both are evaluated at the same 4D space-time point. Notwithstanding its venerable provenance, this equation is incorrect unless the cosmic pressure is 0; but then all that remains of the Einstein equation is the Poisson equation which models the Newtonian gravity field. This shortcoming is not resolved by adding the cosmological constant term to the field equation as in the LCDM model, because then pressure is L, so the pressure is a universal constant, not a variable. Numerous studies support the concept of a linearly expanding universe in which gravitational forces and accelerations are negligible because the baryonic mass density of the universe is far below its critical density. We show that such a coasting universe model agrees with SNe Ia luminosity vs. redshift distances just as well or even better than the LCDM model, and that it does so without having to invoke dark matter or dark energy. Occam’s razor favors a coasting universe over the LCDM model.Ítem The distribution of dark and luminous matter inferred from extended rotation curves(Oxford University Press, 2015-04) Bottema, R.; Garrido Pestaña, J.L.A better understanding of the formation of mass structures in the Universe can be obtained by determining the amount and distribution of dark and luminous matter in spiral galaxies. To investigate such matters a sample of 12 galaxies, most with accurate distances, has been composed of which the luminosities are distributed regularly over a range spanning two and a half orders of magnitude. Of the observed high quality and extended rotation curves of these galaxies decompositions have been made, for four different schemes, each with two free parameters. For a `maximum disc fit' the rotation curves can be well matched, yet a large range of mass-to-light (M/L) ratios for the individual galaxies is required. For the alternative gravitational theory of MOND (Modified Newtonian Dynamics) the rotation curves can be explained if the fundamental parameter associated with MOND is allowed as a free parameter. Fixing that parameter leads to a disagreement between the predicted and observed rotation curves for a few galaxies. When cosmologically motivated NFW dark matter haloes are assumed, the rotation curves for the least massive galaxies can, by no means, be reproduced; cores are definitively preferred over cusps. Finally, decompositions have been made for a pseudo-isothermal halo combined with a universal M/L ratio. For the latter, the light of each galactic disc and bulge has been corrected for extinction and has been scaled by the effect of stellar population. This scheme can successfully explain the observed rotations and leads to submaximum disc mass contributions. Properties of the resulting dark matter haloes are described and a ratio between dark and baryonic mass of ∼9 for the least, and of ∼5, for the most luminous galaxies has been determined, at the outermost measured rotation.