The Universe acceleration from the Unimodular gravity view point: Background and linear perturbations

With the goal of studying cosmological constant (CC) problem, we present an exhaustive analysis unimodular gravity as a possible candidate to resolve CC origin and with this, current Universe acceleration. In this theory, correction (CC-like) in field equations sources late cosmic This is related new parameter, zini, which interpreted redshift CC-like emergence. By comparing value obtained from Planck Supernovaes measurements, it estimate zini=11.15−0.02+0.01 zini=11.43−0.06+0.03 respectively, close reionization epoch. Moreover, use observational Hubble data (OHD), Type Ia Supernovae (SnIa), Baryon Acoustic Oscillations (BAO) Cosmic Microwave Background Radiation (CMB) distance constrain UG parameters. A Joint (OHD+SnIa+BAO+CMB), results zini=11.47−0.073+0.074 within 1σ confidence level consistent our estimation measurements. We also include linear perturbations, starting scalar tensor perturbations complementing perturbed Boltzmann equation for photons. show that 00 term photons contains corrections, meanwhile other are similar those standard cosmology.