Probing alternative cosmologies through the inverse distance ladder

Abstract

We study the implications of a combined analysis of cosmic standard candles and standard rulers on the viability of cosmological models beyond the cosmological concordance model ΛCDM. To this end, we employ well-established data in the form of the joint lightcurve analysis supernova compilation, baryon acoustic oscillations, and cosmic microwave background data on the one hand, and a recently proposed set of quasars as objects of known brightness on the other hand. The advantage of including the latter is that they extend the local distance measures to redshifts which have previously been out of reach and we investigate how this allows one to test cosmologies beyond ΛCDM. While there exist various studies on parametric extensions of ΛCDM, we present here a comparative study of both parametric and fundamental extensions of the standard cosmology. In order to keep the scope of this manuscript contained, we focus on two particular modifications: one is the consistent theory of two interacting spin-2 objects, so-called bigravity, and the other conformal gravity, a theory of gravity that has no knowledge of fundamental length scales. The former of the two constitutes a veritable extension of General Relativity, given that it adds to the metric tensor of gravity a second dynamical tensor field. The resulting dynamics have been proposed as a self-accelerating cosmology. Conformal gravity on the other hand is a much more drastic change of the underlying gravitational theory. Its ignorance towards fundamental length scales offers a completely different approach to the origin of late time acceleration. In this sense, both models offer -in one way or another --an explanation for the dark energy problem. We perform a combined cosmological fit which provides strong constraints on these extensions. We also briefly comment on the implications of the longstanding H 0 -tension.

Constraints on bimetric gravity from Big Bang nucleosynthesis

“…The presence of the massless graviton allows gravitational wave observations to be satisfied without severely restricting the parameter * marcus.hogas@fysik.su.se space of the theory [7], as opposed to many other modified gravity models. Bimetric gravity is also compatible with cosmological observations like the cosmic microwave background (CMB), type Ia supernovae (SNIa), and baryon acoustic oscillations (BAO) [8][9][10][11][12][13][14][15] and it exhibits a screening mechanism that restores general relativity results on solar-system scales [16][17][18][19][20][21]. Among the interesting properties of the theory are:…”

Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

“…These include HIIG starburst galaxy data that reach to ∼ 2.4 (Siegel et al 2005;Plionis et al 2009;Mania & Ratra 2012;Chavez et al 2014;González-Morán et al 2019;Cao et al 2020a,b), quasar angular size measurements that reach to ∼ 2.7 (Gurvits et al 1999;Chen & Ratra 2003a;Cao et al 2017;Ryan et al 2019;Cao et al 2020a,b), and gamma-ray burst observations that reach to ∼ 8.2 (Lamb & Reichart 2000;Wang et al 2016;Demianski et al 2019;Amati et al 2019;Fana Dirirsa et al 2019;Muccino 2020;Luongo & Muccino 2020;Khadka & Ratra 2020c;Cao et al 2020b). Quasar (QSO) X-ray and UV flux measurements that reach to ∼ 7.5 provide another set of data that probe this intermediate redshift region (Risaliti & Lusso 2015Yang et al 2019;Velten & Gomes 2020;Wei & Melia 2020;Lindner et al 2020;Zheng et al 2020;Mehrabi & Basilakos 2020;Khadka & Ratra 2020a,b;Lusso et al 2020;Rezaei et al 2020;Speri et al 2020).…”

Combining cosmological and local bounds on bimetric theory

“…Barionic Acoustic Oscillations (BAOs) are another important tool to constrain background cosmology. We follow a procedure similar to [107], using measurements at 10 different redshifts z = 0.106, 0. The relevant length scale in the case of BAOs is the sound horizon at the drag epoch r s (z d ).…”

“…In this paper, we extend the analysis of [105] to test bimetric cosmology against data from Supernovae type 1a (SN1a), Baryon Acoustic Oscillations (BAOs) and the Cosmic Microwave Background (CMB). While bimetric theory has been tested against these data sets beforehand [60,64,67,68,106,107], here we directly constrain the physical parameters. We restrict our analysis to all theoretically viable bimetric models with up to three free interaction parameters 4 .…”