Browsing by Author "Alvarez, Pedro D."

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    A universe from a Lagrangian fixed point
    (2024) Alvarez, Pedro D.; Koch, Benjamin; Riahinia, Ali; Rincon, Angel
    In this paper, we investigate the theoretical possibility that a Lagrangian fixed point, when applied to cosmological models, can drive dynamical evolution towards a bouncing universe. We analyze the physics of a Lagrangian fixed point within the context of a gravitational average effective action featuring scale-dependent couplings. To explore this concept, we develop a toy model set in a four-dimensional, spatially flat spacetime, anchored by a Lagrangian fixed point. Solving the cosmological equations of this model analytically, we identify several non-trivial solution branches. These branches are characterized by a modified scale factor and dynamic gravitational couplings, offering new insights into the behavior of cosmological models under these conditions.
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    Can scale-dependent cosmology alleviate the H0 tension?
    (2021) Alvarez, Pedro D.; Koch, Benjamin; Laporte, Cristobal; Rincon, Angel
    Scale-dependence is a common feature to all effective models of quantum gravity. In this paper, a cosmological model based on the scale-dependent scenario of gravity is presented. It is argued that such models, where the scale-dependence appears as a correction to the classical Lambda CDM evolution, have the potential of addressing the tensions between early and late time measurements of H-0. After defining criteria to parametrize this tension, we perform a numerical scan over the parameter space of the scale-dependent model, subject to these criteria. In this analysis, it is found that, indeed, the tension can be released.
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    Observational constraints on scale-dependent cosmology
    (2024) Alvarez, Pedro D.; Koch, Benjamin; Laporte, Cristobal; Rincon, Angel
    This paper examines a cosmological model of scale-dependent gravity. The gravitational action is taken to be the Einstein-Hilbert term supplemented with a cosmological constant, where the couplings, G k and A k , run with the energy scale k. Also, notice that, by construction, our formalism recovers general relativity when in the limit of constant Newton's coupling. Two sub-models based on the scale-dependent cosmological model are confronted with recent observational data from: (i) the Hubble parameter H ( z ) , (ii) distance modulus mu ( z ) and (iii) baryon acoustic scale evolution as functions of redshift (BAO). The viability of the model is discussed, obtaining the best-fit parameters and the maximum likelihood contours for these observables. Finally, a joint analysis is performed for H ( z )+ mu ( z )+ BAO.
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    Statefinder analysis of scale-dependent cosmology
    (2022) Alvarez, Pedro D.; Koch, Benjamin; Laporte, Cristobal; Canales, Felipe; Rincon, Angel
    We study the statefinder parameters of a cosmological model based on scale -dependent gravity. The effective Einstein field equations come from an average effective action. From the dynamical system, we derive analytical expressions that improve the con-vergence of the numerical solutions. We determine the statefinder parameters for moderate redshift and compare them with well-known alternatives to ACDM.