Person: López Maroto, Antonio
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 109
PublicationDark energy rest frame and the CMB dipole(American Institute of Physics, 2006) López Maroto, AntonioIf dark energy can be described as a perfect fluid, then, apart from its equation of state relating energy density and pressure, we should also especify the corresponding rest frame. Since dark energy is typically decoupled from the rest of components of the universe, in principle such a frame could be different from that of matter and radiation. In this work we consider the potential observable effects of the motion of dark energy and the possibility to measure the dark energy velocity relative to matter. In particular we consider the modification of the usual interpretation of the CMB dipole and its implications for the determination of matter bulk flows on very large scales. We also comment on the possible origin of a dark energy flow and its evolution in different models. PublicationThe Fisher gAlaxy suRvey cOde (FARO)(IOP Publishing Ltd, 2021-01) Aparicio Resco, Miguel; López Maroto, AntonioThe Fisher gAlaxy suRvey cOde (FARO) is a new public Python code that computes the Fisher matrix for galaxy surveys observables. The observables considered are the linear multitracer 3D galaxy power spectrum, the linear convergence power spectrum for weak lensing, and the linear multitracer power spectrum for the correlation between galaxy distribution and convergence. The code allows for tomographic and model-independent anal- ysis in which, for scale-independent growth, the functions of redshift A(a)(z) sigma(8) (z) b(a)(z), R(z) sigma(8)(z) f(z), L(z) Omega(m) sigma(8)(z) Sigma(z), and E(z) H(z)/H-0, together with the function of scale (P) over cap (k), are taken as free parameters in each redshift and scale bins respectively. In addition, a module for change of variables is provided to project the Fisher matrix on any particular set of cosmological parameters required. The code is built to be fast to compute and user-friendly. As an application example, we forecast the sensitivity of future galaxy surveys like DESI, Euclid, J-PAS and LSST and compare their performance on different redshift and scale ranges. PublicationLa física y los medios audiovisuales(2022-09-12) Ruiz Cembranos, José Alberto; Álvarez Luna, Clara; Ángel Ortega, Sergio; Fernández Sanz, David; López Maroto, Antonio; Pantaleoni González, Michelangelo; Rivas Vargas, Ángel; Rodrigo Somolinos, Pablo FernandoEn este documento se resumen los principales resultados del proyecto de innovación docente titulado “La física y los medios audiovisuales”. Dicho proyecto fue llevado a cabo en la Facultad de Ciencias Físicas de la Universidad Complutense entre los años 2021 y 2022. PublicationCosmological electromagnetic fields and dark energy(Iop Publishing Ltd, 2009-03) López Maroto, Antonio; Beltrán Jiménez, JoséWe show that the presence of a temporal electromagnetic field on cosmological scales generates an effective cosmological constant which can account for the accelerated expansion of the universe. Primordial electromagnetic quantum fluctuations produced during electroweak scale inflation could naturally explain the presence of this field and also the measured value of the dark energy density. The behavior of the electromagnetic field on cosmological scales is found to differ from the well studied short-distance behavior and, in fact, the presence of a non-vanishing cosmological constant could be signalling the breakdown of gauge invariance on cosmological scales. The theory is compatible with all the local gravity tests, and is free from classical or quantum instabilities. Thus we see that, not only the true nature of dark energy can be established without resorting to new physics, but also the value of the cosmological constant finds a natural explanation in the context of standard inflationary cosmology. This mechanism could be discriminated from a true cosmological constant by upcoming observations of CMB anisotropies and large scale structure. PublicationAntiproton signatures from astrophysical and dark matter sources at the galactic center(IOP Publishing, 2015-03) Ruiz Cembranos, José Alberto; Gammaldi, Viviana; López Maroto, AntonioThe center of our Galaxy is a complex region characterized by extreme phenomena. The presence of the supermassive Sagittarius A* black hole, a high dark matter density and an even higher baryonic density are able to produce very energetic processes. Indeed, high energetic gamma-rays have been observed by different telescopes, although their origin is not clear. In this work, we estimate the possible antiproton flux component associated with this signal. The expected secondary astrophysical antiproton background already saturates the observed data. It implies that any other important astrophysical source leads to an inconsistent excess. We estimate the sensitivity of PAMELA to this new primary antiproton source, which depends on the diffusion model and its spectral features. In particular, we consider antiproton spectra described by a power-law, a monochromatic signal and a Standard Model particle-antiparticle channel production. This latter spectrum is typical in the production from annihilating or decaying dark matter. We pay particular attention to the case of a heavy dark matter candidate, which could be associated with the High Energy Stereoscopic System (HESS) data observed from the J1745-290 source. PublicationDark energy in vector-tensor theories of gravity(Iop Publishing Ltd, 2010) López Maroto, Antonio; Beltrán Jiménez, JoséWe consider a general class of vector-tensor theories of gravity and show that solutions with accelerated expansion and a future type III singularity are a common feature in these models. We also show that there are only six vector tensor theories with the same small scales behaviour as General Relativity and, in addition, only two of them can be made completely free from instabilities. Finally, two particular models as candidates for dark energy are proposed: on one hand, a cosmic vector that allows to alleviate the usual naturalness and coincidence problems and, on the other hand, the electromagnetic field is shown to give rise to an effective cosmological constant on large scales whose value can be explained in terms of inflation at the electroweak scale. PublicationAvoiding the dark energy coincidence problem with a cosmic vector(American Institute of Physics, 2009) Beltrán Jiménez, José; López Maroto, AntonioWe show that vector theories on cosmological scales are excellent candidates for dark energy. We consider two different examples, both are theories with no dimensional parameters nor potential terms, with natural initial conditions in the early universe and the same number of free parameters as ACDM. The first one exhibits scaling behaviour during radiation and a strong phantom phase today, ending in a "big-freeze" singularity. This model provides the best fit to date for the SNIa Gold dataset. The second theory we consider is standard electromagnetism. We show that a temporal electromagnetic field on cosmological scales generates an effective cosmological constant and that primordial electromagnetic quantum fluctuations produced during electroweak scale inflation coidd naturally explain, not only the presence of this field, but also the measured value of the dark energy density. The theory is compatible with all the local gravity tests, and is free from classical or quantum instabilities. Thus, not only the true nature of dark energy coidd be estabUshed without resorting to new physics, but also the value of the cosmological constant would find a natural explanation in the context of standard inflationary cosmology. PublicationModified gravity at astrophysical scales(IOP Publishing Ltd, 2019-02-20) Cermeño, M.; Carro, J.; López Maroto, Antonio; Pérez García, M. A.Using a perturbative approach we solve stellar structure equations for low-density (solar-type) stars whose interior is described with a polytropic equation of state in scenarios involving a subset of modified gravity (MG) theories. Rather than focusing on particular theories, we consider a model-independent approach in which deviations from General Relativity are effectively described by a single parameter xi. We find that for length scales below those set by stellar General Relativistic radii the modifications introduced by MG can affect the computed values of masses and radii. As a consequence, the stellar luminosity is also affected. We discuss possible further implications for higher-density stars and observability of the effects previously described. PublicationPossible dark matter origin of the gamma ray emission from the Galactic Center observed by HESS(American Physical Society, 2012-11-06) López Maroto, Antonio; Ruiz Cembranos, José Alberto; Gammaldi, VivianaWe show that the gamma ray spectrum observed with the HESS array of Cherenkov telescopes coming from the Galactic Center region and identified with the source HESS J1745-290 is well fitted by the secondary photons coming from dark matter (DM) annihilation over a diffuse power law background. The amount of photons and morphology of the signal localized within a region of few parsecs, require compressed DM profiles as those resulting from baryonic contraction, which offer 103 enhancements in the signal over DM alone simulations. The fitted background from HESS data is consistent with recent Fermi-LAT observations of the same region. PublicationBlack holes in f(R) theories(American Physical Society, 2009-12) Cruz Dombriz, Álvaro de la; Dobado González, Antonio; López Maroto, AntonioIn the context of f(R) theories of gravity, we address the problem of finding static and spherically symmetric black hole solutions. Several aspects of constant curvature solutions with and without electric charge are discussed. We also study the general case (without imposing constant curvature). Following a perturbative approach around the Einstein-Hilbert action, it is found that only solutions of the Schwarzschild-(anti) de Sitter type are present up to second order in perturbations. Explicit expressions for the effective cosmological constant are obtained in terms of the f(R) function. Finally, we have considered the thermodynamics of black holes in anti-de Sitter space-time and found that this kind of solution can only exist provided the theory satisfies R(0)+f(R(0))<0. Interestingly, this expression is related to the condition which guarantees the positivity of the effective Newton's constant in this type of theories. In addition, it also ensures that the thermodynamical properties in f(R) gravities are qualitatively similar to those of standard general relativity.