arXiv subjects

Alexander Bonilla Rivera

Publications and source records attributed to Alexander Bonilla Rivera.

5 recordsLinked to original sources

arXiv2026

The LISA Astrophysics MBHcatalogues Project: A comparison of predictions of simulated massive black hole binaries

In the hierarchical paradigm of galaxy formation, central massive black holes (MBHs) are expected to coalesce after the merger of their host galaxies. One of the main goals of the Laser Interferometer Space Antenna (LISA) is to constrain the origin and growth of MBHs through their merger rates and mass distribution. Predicting MBH merger rates requires not only tracing their statistical population from large to small physical scales (kpc to sub-pc) but also modelling their formation, accretion, dynamics, mergers, and their galactic physical processes across cosmic time. This project is the result of a large collaborative effort undertaken by the LISA Astrophysics Working Group, bringing together its collective expertise on MBH formation, evolution, and modelling, to build a comprehensive understanding of MBH merger rates across cosmic time. The project compares various theoretical predictions of MBH merger rates, quantifies the spread, and evaluates the global astrophysical uncertainties of the LISA event rates. To build a unique and complete view, our work is based on about 20 semi-analytical models and cosmological simulations from the literature, all employing distinct approaches to modelling MBH and galaxy physics. To compute the merger rates, we also incorporate delays arising from the dynamical phase of MBH hardening to coalescence. We present the expected LISA merger rates given current galaxy formation models and discuss how the merger rate depends on model assumptions, such as the seeding model and the resolution of cosmological simulations.

astro-ph.GA↗

arXiv2025

Revisiting the temperature evolution law of the CMB with gaussian processes

In this work, we perform a statistical inference of the classical background law governing the evolution of the temperature of the cosmic microwave background radiation (CMB), given by $T_{\rm CMB}(z) = T_0(1 + z)$. To this end, we employ Gaussian Process (GP) regression techniques to reconstruct the temperature evolution based on two observational datasets: (i) CMB-Sunyaev-Zel'dovich (SZ) cluster measurements and (ii) CMB-interstellar medium (ISM) interaction data. Our analysis reveals interesting results that may suggest potential deviations from the standard temperature-redshift relation, particularly at low redshifts ($z < 0.5$), where discrepancies up to $\sim$2$σ$ are observed. Additionally, we identify a mild but noteworthy tension, also at the $\sim$2$σ$ level, between our GP inferred value of the present-day CMB temperature, $T_{\rm CMB}(z=0)$, and the precise direct measurement from the COBE/FIRAS experiment. We also explore possible phenomenological implications of our findings, including interpretations associated with possible variations in fundamental constants, such as the fine-structure constant $α$, which could provide a physical explanation for the observed deviations at low redshift.

astro-ph.CO↗

arXiv2019

Exploring the Dark Universe: constraints on dynamical Dark Energy models from CMB, BAO and growth rate measurements

In order to explain the current acceleration of the Universe, the fine tuning problem of the cosmological constant $Λ$ and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the most recent observational data from CMB (Planck 2018 final data release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy (DE) models. The CMB shift parameter, which traditionally has been used to determine the main cosmological parameters of the standard model $ΛCDM$ is employed in addition to data from redshift-space distortions through the growth parameter $A(z)=f(z)σ_{8}(z)$ to constrain the mass variance $σ_{8}$. BAO data is also used to study the history of the cosmological expansion and the main properties of DE. From the evolution of $q(z)$ we found a slowdown of acceleration behaviour at low redshifts, and by using the Akaike and Bayesian Information Criterion (AIC, BIC) we discriminate different models those that are better suited to the observational data, finding that the interactive dark energy (IDE) model is the most favoured by observational data, including information from SNIa and Hz. The analysis shows that the IDE model is followed closely by EDE and $ΛCDM$ models, which in some cases fit better the observational data with individual probes.

astro-ph.CO↗

arXiv2016

Constraints On Holographic Cosmological Models From Gamma Ray Bursts

We use Gamma Ray Bursts (GRBs) data from Y. Wang (2008) to put additional constraints on a set of cosmological dark energy models based on the holographic principle. GRBs are among the most complex and energetic astrophysical events known in the universe offering us the opportunity to obtain information from the history of cosmic expansion up to about redshift of $z\sim 6$. These astrophysical objects provide us a complementary observational test to determine the nature of dark energy by complementing the information of data from Supernovas (e.g. Union 2.1 compilation). We found that the $ΛCDM$ model gives the best fit to the observational data, although our statistical analysis ($ΔAIC$ and $ΔBIC$) shows that the models studied in this work ("Hubble Radius Scale" and "Ricci Scale Q") have a reasonable agreement with respect to the most successful, except for the "Ricci Scale CPL" and "Future Event Horizon" models, which can be ruled out by the present study. However, these results reflect the importance of GRBs measurements to provide additional observational constraints to alternative cosmological models, which are mandatory to clarify the way in which the paradigm of dark energy or any alternative model is correct.

astro-ph.CO↗

arXiv2016

Theoretical Foundations of PGWs Printed in the CMB and its Observational Status

The anisotropy study cosmic microwave background (CMB) is one of the main observational tools for modern cosmology. However, alongside the study of the thermal fluctuations of the CMB are other equally important information, which is known as the polarization of the CMB. The inflationary model predicts that the CMB is linearly polarized and the physical mechanism of this polarization is studied from the Thompson scattering, the dominant process on the surface of last scattering. There are basically two types of polarization called E and B modes, the first produced by scalar perturbations and the latter by tensor perturbations, such as those due to gravitational waves in the primordial universe. So if we are able to measure these types of polarization will have an entry to the study of the inflationary epoch. This paper presents the main physical mechanisms that support theoretically the polarization of the CMB due to primordial gravitational waves (PGW) and the revision of the main observables, grouped in so-called Stokes parameters (Q, U, I), Which brings us information to achieve the contrast the angular power spectrum produced by the polarization of the CMB, which shows to be in excellent agreement with the $Λ$CDM model.

astro-ph.CO↗