Person: Aparicio Resco, Miguel
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First Name
Miguel
Last Name
Aparicio Resco
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física Teórica
Area
Física Teórica
Identifiers
10 results
Search Results
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Item On neutron stars in f (R) theories: Small radii, large masses and large energy emitted in a merger(Physics of the dark universe, 2016) Aparicio Resco, Miguel; Cruz Dombriz, Álvaro de la; Llanes Estrada, Felipe José; Zapatero Castrillo, VíctorIn the context of f(R) gravity theories, we show that the apparent mass of a neutron star as seen from an observer at infinity is numerically calculable but requires careful matching, first at the star’s edge, between interior and exterior solutions, none of them being totally Schwarzschildlike but presenting instead small oscillations of the curvature scalar R; and second at large radii, where the Newtonian potential is used to identify the mass of the neutron star. We find that for the same equation of state, this mass definition is always larger than its general relativistic counterpart. We exemplify this with quadratic R 2 and Hu-Sawicki-like modifications of the standard General Relativity action. Therefore, the finding of two-solar mass neutron stars basically imposes no constraint on stable f(R) theories. However, star radii are in general smaller than in General Relativity, which can give an observational handle on such classes of models at the astrophysical level. Both larger masses and smaller matter radii are due to much of the apparent effective energy residing in the outer metric for scalar-tensor theories. Finally, because the f(R) neutron star masses can be much larger than General Relativity counterparts, the total energy available for radiating gravitational waves could be of order several solar masses, and thus a merger of these stars constitutes an interesting wave source.Item Parametrizations and forecasts for non-standard cosmological models with galaxy surveys(2021) Aparicio Resco, Miguel; López Maroto, AntonioThe next generation of galaxy surveys will shed new light on our understanding of the Universe on large scales. Thanks to the large number of galaxies and the accuracy of these galaxy maps, the cosmological parameters will be measured at the 1% level and below. This makes it necessary to develop forecast analysis to explore what are the parameters that galaxy surveys will constrain with better accuracy, and also the best configurations of these surveys to exploit the maximum potential of the observables. From the theoretical point of view, there are many different models that have been proposed in recent years to describe the yet unknown dark sector of cosmology. Regarding models for the late-time accelerated expansion of the Universe, they can be classified in twotypes: dark energy models and modified gravity models. The former considers a modification in the matter-energy term, this modification extends the constant dark energy term of CDM model into a dynamical dark energy. Instead, modified gravity models consider a modification in the gravity term that generates accelerated expansion...Item The Fisher gAlaxy suRvey cOde (FARO)(Journal of cosmology and astroparticle physics., 2021) 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.Item Testing for gravitational preferred directions with galaxy and lensing surveys(Journal of cosmology and astroparticle physics, 2020) Aparicio Resco, Miguel; López Maroto, AntonioWe analyze the sensitivity of galaxy and weak-lensing surveys to detect preferred directions in the gravitational interaction. We consider general theories of gravity involving additional vector degrees of freedom with non-vanishing spatial components in the background. We use a model-independent parametrization of the perturbations equations in terms of four effective parameters, namely, the standard effective Newton constant G(eff) and slip parameter gamma for scalar modes and two new parameters mu(Q) and mu(h) for vector and tensor modes respectively, which are required when preferred directions are present. We obtain the expressions for the multipole galaxy power spectrum in redshift space and for the weak-lensing shear, convergence and rotation spectra in the presence of preferred directions. By performing a Fisher matrix forecast analysis, we estimate the sensitivity of a future Euclid-like survey to detect this kind of modification of gravity. We finally compare with the effects induced by violations of statistical isotropy in the primordial power spectrum and identify the observables which could discriminate between them.Item Modified gravity or imperfect dark matter: a model-independent discrimination(Journal of cosmology and astroparticle physics., 2021) Aparicio Resco, Miguel; López Maroto, AntonioWe analyze how to parametrize general modifications of the dark matter perturbations equations in a model-independent way. We prove that a general model with an imperfect and non-conserved dark matter fluid with bulk and shear viscosities and heat flux in a modified gravity scenario can be described with five general functions of time and scale. We focus on the sub-Hubble regime within the quasi-static approximation and calculate the observable power spectra of the galaxy distribution, galaxy velocities and weak lensing and find that these observables are only sensitive to three combinations of the initial five functions. Deviations of these three observable functions with respect to ACDM give us different characteristic signals which allow us to determine in which cases it is possible to discriminate a modification of gravity from an imperfect or non-conserved dark matter. Finally, we perform a Fisher forecast analysis for these three parameters and show an example for a particular model with shear viscosity.Item Parametrizing modified gravities with vector degrees of freedom: anisotropic growth and lensing(Journal of cosmology and astroparticle physics, 2018) Aparicio Resco, Miguel; López Maroto, AntonioWe consider the problem of parametrizing modified gravity theories that include an additional vector field in the sub-Hubble regime within the quasi-static approximation. We start from the most general set of second order equations for metric and vector field perturbations and allow for both temporal and spatial components of the background vector field. We find that in the case in which dark matter obeys standard conservation equations, eight parameters are needed to fully characterize the theory. If dark matter vorticity can be neglected, the number of independent parameters is reduced to four. In addition to the usual scale and redshift dependence, the effective parameters have an additional angular dependence induced by the preferred direction set by the background vector. In the considered sub-Hubble regime, we show that this angular dependence appears only through even multipoles and generates anisotropies in the growth function which translate into anisotropies in the galaxy and lensing convergence power spectra. The angular dependence generated by the preferred direction is different from that induced by redshift space distortions and could be disentangled in the data collected by future galaxy surveys.Item J-PAS: forecasts for dark matter-dark energy elastic couplings(Journal of cosmology and astroparticle physics, ) Aparicio Resco, Miguel; López Maroto, Antonio; otros, ...We consider a cosmological model where dark matter and dark energy feature a coupling that only affects their momentum transfer in the corresponding Euler equations. We perform a fit to cosmological observables and confirm previous findings within these scenarios that favour the presence of a coupling at more than 3a. This improvement is mainly driven by cluster counts from Planck Sunyaev-Zeldovich data that we include as a certain prior. We subsequently perform a forecast for future J-PAS data and find that clustering measurements will permit to clearly discern the presence of an interaction within a few percent level with the uncoupled case at more than 10o(-) when the complete survey, covering 8500 sq. deg., is considered. We found that the inclusion of weak lensing measurements will not help to further constrain the coupling parameter. For completeness, we compare to forecasts for DESI and Euclid, which provide similar discriminating power.Item On neutron stars in ƒ (R) theories: Small radii, large masses and large energy emitted in a merger(Physics of the dark universe, 2016) Aparicio Resco, Miguel; Cruz Dombriz, Álvaro de la; Llanes Estrada, Felipe José; Zapatero Castrillo, VíctorIn the context of ƒ (R) gravity theories, we show that the apparent mass of a neutron star as seen from an observer at infinity is numerically calculable but requires careful matching, first at the star’s edge, between interior and exterior solutions, none of them being totally Schwarzschild-like but presenting instead small oscillations of the curvature scalar R; and second at large radii, where the Newtonian potential is used to identify the mass of the neutron star. We find that for the same equation of state, this mass definition is always larger than its general relativistic counterpart. We exemplify this with quadratic R^2 and Hu-Sawicki-like modifications of the standard General Relativity action. Therefore, the finding of two-solar mass neutron stars basically imposes no constraint on stable ƒ (R) theories. However, star radii are in general smaller than in General Relativity, which can give an observational handle on such classes of models at the astrophysical level. Both larger masses and smaller matter radii are due to much of the apparent effective energy residing in the outer metric for scalar-tensor theories. Finally, because the ƒ (R) neutron star masses can be much larger than General Relativity counterparts, the total energy available for radiating gravitational waves could be of order several solar masses, and thus a merger of these stars constitutes an interesting wave source.Item Parametrizing growth in dark energy and modified gravity models(Physical review D, 2018) Aparicio Resco, Miguel; López Maroto, AntonioIt is well known that an extremely accurate parametrization of the growth function of matter density perturbations in ACDM cosmology, with errors below 0.25%, is given by f(a) = Ω^(γ)_(m)(a) with γ ≃ 0.55. In this work, we show that a simple modification of this expression also provides a good description of growth in modified gravity theories. We consider the model-independent approach to modified gravity in terms of an effective Newton constant written as μ(a, k) = G_(eff)/G and show that f(a) = β(a) Ω^(γ)_(m)(a) provides fits to the numerical solutions with similar accuracy to that of ACDM. In the time-independent case with μ ¼ μðkÞ, simple analytic expressions for βðμÞ and γðμÞ are presented. In the time-dependent (but scaleindependent) case μ = μ(a), we show that β(a) has the same time dependence as μ(a). As an example, explicit formulas are provided in the Dvali-Gabadadze-Porrati (DGP) model. In the general case, for theories with μ(a, k), we obtain a perturbative expansion for β(μ) around the general relativity case μ = 1 which, for f(R) theories, reaches an accuracy below 1%. Finally, as an example we apply the obtained fitting functions in order to forecast the precision with which future galaxy surveys will be able to measure the μ parameter.Item J-PAS: forecasts on dark energy and modified gravity theories(Monthly notices of the royal astronomical society, 2020) Aparicio Resco, Miguel; López Maroto, Antonio; otros, ...The next generation of galaxy surveys will allow us to test one of the most fundamental assumptions of the standard cosmology, i.e. that gravity is governed by the general theory of relativity (GR). In this paper, we investigate the ability of the Javalambre Physics of the AcceleratingUniverseAstrophysical Survey (J-PAS) to constrainGR and its extensions. Based on the J-PAS information on clustering and gravitational lensing, we perform a Fisher matrix forecast on the effective Newton constant, mu, and the gravitational slip parameter, eta, whose deviations from unity would indicate a breakdown of GR. Similar analysis is also performed for the DESI and Euclid surveys and compared to J-PAS with two configurations providing different areas, namely an initial expectation with 4000 deg(2) and the future best case scenario with 8500 deg(2). We show that J-PAS will be able to measure the parameters mu and eta at a sensitivity of 2-7 per cent, and will provide the best constraints in the interval z = 0.3-0.6, thanks to the large number of ELGs detectable in that redshift range. We also discuss the constraining power of J-PAS for dark energy models with a time-dependent equation-of-state parameter of the type w(a) = w(0) + w(a)(1 - a), obtaining Delta w(0) = 0.058 and Delta w(a) = 0.24 for the absolute errors of the dark energy parameters.