Nonminimal dark sector physics and cosmological tensions

Abstract

We explore whether non-standard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are: (a) an interaction between the dark matter and dark energy components, and (b) a dark energy equation of state w different from that of the canonical cosmological constant w = −1. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. Moreover, a clear degeneracy exists between these two parameters in the case of Cosmic Microwave Background (CMB) data. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder H0 measurements of Riess et al. (R19), as well as recent Baryon Acoustic Oscillation (BAO) and Type Ia Supernovae (SNeIa) distance data. We find that in quintessence coupled dark energy models, where w > −1, the evidence for a non-zero coupling between the two dark sectors can surpass the 5σ significance. Moreover, for both Planck+BAO or Planck+SNeIa, we found a preference for w > −1 at about three standard deviations. Quintessence models are, therefore, in excellent agreement with current data when an interaction is considered. On the other hand, in phantom coupled dark energy models, there is no such preference for a non-zero dark sector coupling. All the models we consider significantly raise the value of the Hubble constant easing the H0 tension. In the interacting scenario, the disagreement between Planck+BAO and R19 is considerably reduced from 4.3σ in the case of ΛCDM to about 2.5σ. The addition of low-redshift BAO and SNeIa measurements leaves, therefore, some residual tension with R19 but at a level that could be justified by a statistical fluctuation. We conclude that non-minimal dark energy cosmologies, such as coupled quintessence or phantom models, may soften the existing cosmological tensions. * eleonora.divalentino@manchester.ac.uk † alessandro.melchiorri@roma1.infn.it ‡ omena@ific.uv.es § sunny.vagnozzi@ast.cam.ac.uk 1 In Ref. [15,16] the reader can find complete reviews comparing the CMB and local determinations of H 0 .

On quintessence star model and strange star

“…For quintessence with a speed of sound equal to zero, quintessence perturbations induce effects on the evolution of structures particularly when the dark energy component comes to dominate the energy density of the universe [11], just to mention an example. Other more recent work shows elements in favor of quintessence both from the theoretical point of view and as regards their consistency with the observations [13][14][15][16][17][18][19].…”

All-inclusive interacting dark sector cosmologies

“…5 and Ref. [58,67]. For this very same reason the CMB+R19 data combination prefers a non-zero value of the coupling ξ at a very high significance level.…”

“…This is mainly due to the energy flow between the dark sectors, which, for this phantom case with ξ < 0 (i.e. energy flux flowing from DE to DM) results in a larger density for cold dark matter at present, see also [58]. Also, the Hubble constant is always much larger than in the canonical ΛCDM scenario when considering CMB only, due to the fact that in the phantom region there is a strong degeneracy between w x and H 0 at the level of the CMB (see Fig.…”

Constraints and cosmography of $$\Lambda $$CDM in presence of viscosity

“…Indeed, the viscous models could affront problems like the H 0 tension, and the problem associated with the matter fluctuation amplitude. This kind of models also have the characteristic of predicting an earlier transition to an accelerated phase in comparison with the standard cosmological model (see for example [24][25][26]). This is because the causative of the Universe acceleration could be related with a dynamical DE and not a cosmological constant as states the consensus model.…”