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 theory of a massive tensor field interacting with the standard metric of gravity, 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 late time acceleration and the so-called cosmological constant problem. In this sense, both models offer -in one way or another -an explanation for the cosmological constant problem. We perform a combined cosmological fit which provides strong constraints on some of these extensions, while some alternative cosmologies are in fact favoured by the data. We also briefly comment on the implications of the long-standing H 0 -tension.

On Larger $H_0$ Values in the CMB Dipole Direction

“…Obviously, both QSOs and GRBs are not widely used in cosmology, although this is changing in recent years [79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95]. Both have great potentials as they probe redshift ranges not accessible by other probes.…”

Physical parameter space of bimetric theory and SN1a constraints

“…As a consequence, refs. [14][15][16]28] test the region where the Fierz-Pauli mass is comparable to the Hubble rate today. This parameter region is the relevant one for addressing the H 0 -tension [76].…”

“…In refs. [15,16,28] either the rescaled parametrization with α = 1 is used or B n ∼ O(1) is assumed implying that their results apply only to a small region of the parameter space. As a consequence, refs.…”

“…Of course, bimetric theory has been compared to cosmological data previously on both the background and perturbative level, see, e.g., refs. [14][15][16][17][25][26][27][28]. All these studies found various (sub-)models that give rise to a viable background cosmology which can compete with General Relativity.…”

Cosmological parameter analyses using transversal BAO data

“…Nowadays are stimulating for cosmology, with a plethora of dark energy models competing to describe the current high-quality cosmological observations [1,2]. The combination of data from cosmological probes like standard candles, from type Ia supernovae data [3], standard rulers, from Baryon Acoustic Oscillations (BAO) data [4][5][6], together with measurements of the cosmic microwave background (CMB) radiation [7,8] have produced precise parameters constraints of the concordance cosmological model, the spatially flat ΛCDM [8][9][10], strongly restricting alternative scenarios (see, e.g., [11][12][13][14][15][16][17][18][19][20]).…”