Hubble expansion and structure formation in the ``running FLRW model'' of the cosmic evolution

Abstract

A new class of Friedmann-Lemaître-Robertson-Walker (FLRW) cosmological models with time-evolving fundamental parameters should emerge naturally from a description of the expansion of the universe based on the first principles of quantum field theory and string theory. Within this general paradigm, one expects that both the gravitational Newton's coupling G and the cosmological term Λ should not be strictly constant but appear rather as smooth functions of the Hubble rate H(t). This scenario ("running FLRW model") predicts, in a natural way, the existence of dynamical dark energy without invoking the participation of extraneous scalar fields. In this paper, we perform a detailed study of some of these models in the light of the latest cosmological data, which serves to illustrate the phenomenological viability of the new dark energy paradigm as a serious alternative to the traditional scalar field approaches. By performing a joint likelihood analysis of the recent supernovae type Ia data (SNIa), the Cosmic Microwave Background (CMB) shift parameter, and the Baryonic Acoustic Oscillations (BAOs) traced by the Sloan Digital Sky Survey (SDSS), we put tight constraints on the main cosmological parameters. Furthermore, we derive the theoretically predicted dark-matter halo mass function and the corresponding redshift distribution of cluster-size halos for the "running" models studied. Despite the fact that these models closely reproduce the standard ΛCDM Hubble expansion, their normalization of the perturbation's power-spectrum varies, imposing, in many cases, a significantly different cluster-size halo redshift distribution. This fact indicates that it should be relatively easy to distinguish between the "running" models and the ΛCDM using realistic future X-ray and Sunyaev-Zeldovich cluster surveys.

Starobinsky-Like Inflation and Running Vacuum in the Context of Supergravity

“…The dimensionless coefficient α is also small, |α| 1, because the inflationary scale H I is certainly below the Planck scale; see Equation (3). From the observational viewpoint, utilizing a joint likelihood analysis of the recent supernovae Type Ia data, the CMB shift parameter and the baryonic acoustic oscillations, it has been found |ν| = O(10 −3 ) [29,30,32,33], which is nicely in accordance with the aforementioned theoretical expectations, as well as it ensures a mild dynamical behaviour of the vacuum energy at low energies. As we have already stated in Section 2, the quantum-gravity corrections in the Starobinsky model have been found in the context of the RG analysis [54][55][56] through the appropriate beta-functions.…”

“…The implications of these dynamical vacuum models have recently been analysed both for the early Universe [22][23][24][25][26][27][28], as well as for the phenomenology of the current Universe [29][30][31]; see also [32][33][34][35][36][37][38][39][40] for previous analyses.…”

Running vacuum cosmological models: linear scalar perturbations

“…These models were confronted with observations -supernovae, baryon acoustic oscillations (BAO), CMB, and large scale structure -giving promising results [22,36,[41][42][43][44][45][46]. In another approach, the CC problems have motivated the interest on the dynamical quantum effects on the vacuum energy density in quantum field theory, and their possible link and implications to DE concept in cosmology.…”

Cosmology with Varying Constants from a Thermodynamic Viewpoint

“…We compare our model with the data from supernovae, Baryon Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB). Our model is also related to dynamical vacuum energy models, which have been discussed and confronted with data [11][12][13][14][30][31][32]. Similarly, dynamical dark energy models with varying fundamental constants have been discussed in [33,34].…”

“…If we use the ansätze c = c 0 a n and G = G 0 a q in the above-modified equations of motion, then these equations are analogous to the entropic force expressions [15][16][17] and running vacuum models [11][12][13][14][30][31][32]. We consider the multiple fluid scenario, and using the barotropic equation of state p i = w i ρ i , we solve the modified continuity equation…”