Can Dark Energy Emerge from a Varying $G$ and Spacetime Geometry?

Abstract

The accelerated expansion of the universe implies the existence of an energy contribution known as dark energy. Associated with the cosmological constant in the standard model of cosmology, the nature of this dark energy is still unknown. We will discuss an alternative gravity model in which this dark energy contribution emerges naturally, as a result of allowing for a time-dependence on the gravitational constant, $G$, in Einstein's field equations. With this modification, Bianchi's identities require an additional tensor field to be introduced so that the usual conservation equation for matter and radiation is satisfied. The equation of state of this tensor field is obtained using additional constraints, coming from the assumption that this tensor field represents the space-time response to the variation of $G$. We will also present the predictions of this model for the late-universe data, and show that the energy contribution of this new tensor is able to explain the accelerated expansion of the universe without the addition of a cosmological constant. Unlike many other alternative gravities with varying gravitational strength, the predicted $G$ evolution is also consistent with local observations and therefore this model does not require screening. We will finish by discussing possible other implications this approach might have for cosmology and some future prospects.

arXiv commentPrepared for the proceedings of Alternative Gravities and Fundamental Cosmology - ALTECOSMOFUN'21 (https://indico.cern.ch/event/873762/) conference. Matches the version published at Universe Special Issue: Alternative Gravities and Fundamental Cosmology

References in corpus (18)

• The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample
• The 6dF Galaxy Survey: Baryon Acoustic Oscillations and the Local Hubble Constant
• Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples
• The Clustering of the SDSS DR7 Main Galaxy Sample I: A 4 per cent Distance Measure at z=0.15
• Observational Probes of Cosmic Acceleration
• Progress in Lunar Laser Ranging Tests of Relativistic Gravity
• Beyond $\Lambda$CDM: Problems, solutions, and the road ahead
• Measurement of BAO correlations at $z=2.3$ with SDSS DR12 \lya-Forests
• Baryon acoustic oscillations from the complete SDSS-III Ly$\alpha$-quasar cross-correlation function at $z=2.4$
• Bounds on the possible evolution of the Gravitational Constant from Cosmological Type-Ia Supernovae
• The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: structure growth rate measurement from the anisotropic quasar power spectrum in the redshift range $0.8<z<2.2$
• How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe
• Type Ia supernovae, standardisable candles, and gravity
• Screened Fifth Forces Mediated by Dark Matter-Baryon Interactions: Theory and Astrophysical Probes
• Can the fluctuations of the quantum vacuum solve the cosmological constant problem?
• Can the quantum vacuum fluctuations really solve the cosmological constant problem?
• Evidence for the Fifth Element Astrophysical status of Dark Energy
• Time-dependent $G$ in Einstein's equations as an alternative to the cosmological constant

Cited by in corpus (1)

• Testing a varying-$\Lambda$ model for dark energy within Co-varying Physical Couplings framework