Observational Constraints in Delta-gravity: CMB and Supernovae

Abstract

Delta-gravity (DG) is a gravitational model based on an extension of general relativity given by a new symmetry called . In this model, new matter fields are added to the original matter fields, motivated by the additional symmetry. We call them matter fields. This model predicts an accelerating universe without the need to introduce a cosmological constant. In this work, we study the scalar cosmic microwave background (CMB) temperature (TT) power spectrum predicted by DG using an analytical hydrodynamic approach. To fit the Planck satellite’s data with the DG model, we used a Markov Chain Monte Carlo analysis. We also include a study about the compatibility between Type Ia supernovae (SNe Ia) and CMB observations in the DG context. Finally, we obtain the scalar CMB TT power spectrum and the fitted parameters needed to explain both SN Ia data and CMB measurements. The results are in reasonable agreement with both observations considering the analytical approximation. We also discuss whether the Hubble constant and the accelerating universe are in concordance with the observational evidence in the DG context.

Cosmological Fluctuations in Delta Gravity

“…With the full scalar expression for the CMB power spectrum coefficients, we can find the shape of the spectrum. The full analysis and results can be found in [49]. The principal purpose of this work was to present the derivation of this expression and obtain physical insight into the cosmological fluctuations in delta gravity.…”

“…In the work conducted in ApJ [49], the shape of the temperature power spectrum is determined by five free parameters. These parameters were explored using a modified adaptive Metropolis MCMC algorithm.…”

“…By studying the CMB anisotropies, we can address two aspects: the compatibility between the CMB power spectrum and DG fluctuations and the compatibility between CMB and SNe-Ia in the DG theory. In [49], we already fitted Planck satellite's data with a DG model using Markov Chain Monte Carlo analysis. We also studied the compatibility between SNe Ia and CMB observation in this framework.…”

Hubble tension and matter inhomogeneities: a theoretical perspective

“…This controversy opens a window for new alternative theories based on modifications or variations of ΛCDM such as (Haslbauer et al 2020;Camarena & Marra 2018;Huang & Wang 2016;Li et al 2013;Cedeño et al 2019;Xu et al 2019;Deser & Woodard 2019;Anagnostopoulos et al 2019;Poulin et al 2018;Martín et al 2021), other proposals introduce modifications in the physics of neutrinos, for example (Battye & Moss 2014;Zhang et al 2014;Bernal et al 2016;Valentino & Bouchet 2016;Feng et al 2017;Zhao et al 2017;Benetti et al 2017;Feng et al 2018;Zhao et al 2018;Benetti et al 2018;Choudhury & Choubey 2019;Carneiro et al 2019;Nakamura et al 2019) and others consider that DE can couple with DM: (Salvatelli et al 2013;Costa et al 2014;Yang et al 2017;Di Valentino et al 2017b;Feng et al 2019;Yang et al 2018).…”