Relaxing cosmological tensions with a sign switching cosmological constant

Abstract

We present a further observational analysis of the ΛsCDM model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)]. This model is based on the the recent conjecture suggesting the universe has transitioned from anti-de Sitter vacua to de Sitter vacua (viz., the cosmological constant switches sign from negative to positive), at redshift z † ∼ 2, inspired by the graduated dark energy (gDE) model proposed in Akarsu et al. [Phys. Rev. D 101, 063528 (2020)]. ΛsCDM was previously claimed to simultaneously relax five cosmological discrepancies, namely, the H0, S8, and MB tensions along with the Ly-α and ω b anomalies, which prevail within the standard ΛCDM model as well as its canonical/simple extensions. In the present work, we extend the previous analysis by constraining the model using the Pantheon data (with and without the SH0ES MB prior) and/or the completed BAO data along with the full Planck CMB data. We find that ΛsCDM exhibits a better fit to the data compared to ΛCDM, and relaxes the six discrepancies of ΛCDM, namely, the H0, MB, S8, Ly-α, t0, and ω b discrepancies, each one discussed in detail. When the MB prior is included in the analyses, ΛsCDM performs significantly better in relaxing the H0, MB, and S8 tensions with the constraint z † ∼ 1.8 even when the Ly-α data (which imposed the z † ∼ 2 constraint in the previous studies) are excluded. In contrast, the presence of the MB prior causes only negligible improvements for ΛCDM. Thus, the ΛsCDM model provides remedy to various cosmological tensions simultaneously, only that the galaxy BAO data hinder its success to some extent.

Cosmological direct detection of dark energy: non-linear structure formation signatures of dark energy scattering with visible matter

“…In addition, we further note that the possibility of a negative CC contributing to the DE sector in combination with a quintessence component is in perfect agreement with current cosmological data (see e.g. Dutta et al 2020;Calderón et al 2021;Bonilla et al 2021;Acquaviva et al 2021;Akarsu et al 2021;Sen et al 2021). 2 For examples of important works on theoretical and observational aspects of coupled DE, see for instance Wetterich (1995); Amendola (2000); Mangano et al (2003); Farrar & Peebles (2004); Barrow & Clifton (2006); Pettorino & Baccigalupi (2008); Valiviita et al (2008); Gavela et al (2009); Clemson et al (2012); Nunes & Barboza (2014); Benisty & Guendelman (2017); Kumar & Nunes (2017b); Yang et al (2017Yang et al ( , 2018a; Martinelli et al (2019); Kumar et al (2019); Yang et al (2019a,c); Benetti et al (2019); Di Valentino et al (2020); Lucca & Hooper (2020); Hogg et al (2020); Gómez-Valent et al (2020); Gao et al (2021); Zhang et al (2021); Benetti et al (2021); Kumar (2021); Lucca (2021a,b).…”

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

“…It was shown in Ref. [558] that, when the consistency of the Λ s CDM model with the CMB data is guaranteed, (i) H 0 and M B (SNIa absolute magnitude) values are inversely correlated with z † and reach H 0 ≈ 74.5 km s −1 Mpc −1 and M B ≈ −19.2 mag for z † = 1.5, in agreement with the measurements from SH0ES [93,109], and (ii) H(z) presents an excellent fit to the Ly-α data provided that z † 2.34. The assessment of the model against Planck 2018 yields H 0 = 70.22 ± 1.78 km s −1 Mpc −1 and against Planck 2018 + SDSS DR16 yields H 0 = 68.82 ± 0.55 km s −1 Mpc −1 with z † = 2.44 ± 0.29 [558].…”

“…Among the variety of cosmological models (in alphabetical order) presented below, some of them have been proposed by many researchers to either alleviate or solve the S 8 tension C. Addressing Both the H0 and S8 Tensions Thus, looking for a cosmological model accommodating both the tensions is not a cup of tea. Nevertheless, curious minds never stop at any point and as a result it has been argued that in some extended cosmological models beyond ΛCDM, one can simultaneously tackle this problem [552][553][554][555][556][557][558][559]. However, even though we have a series of alternative possibilities beyond the standard ΛCDM model, we are still left with some vital issues that are usually overlooked while discussing the simultaneous solutions to both the tensions.…”

“…Inspired by these observational findings, and the theoretically compelling fact that the gDE submits to the weak energy condition and the bounds on the speed of sound only in the limit λ → −∞ which corresponds to a cosmological constant that rapidly changes sign at redshift z † , this limit was dubbed Λ s CDM and further investigated in Ref. [558]. The Λ s CDM model can be constructed phenomenologically by simply replacing the usual cosmological constant (Λ) of the standard ΛCDM model with a cosmological constant (Λ s ) that switches its sign from negative to positive, and thus attains its present-day value (Λ s0 > 0), when the Universe reaches a certain energy scale (redshift z † ) during its expansion,…”

Testing dark energy after pre-recombination early dark energy

“…The beyond-ΛCDM modifications after recombination have also been proposed e.g. [38][39][40][41][42][43][44][45][46][47][48][49], see also [50,51] for recent reviews. The current accelerated expansion of our Universe suggests the existence of dark energy at present, with the equation of state (EOS) w = p/ρ −1.…”