Testing non-local gravity by clusters of galaxies

Abstract

Extended theories of gravity have been extensively investigated during the last thirty years, aiming at fixing infrared and ultraviolet shortcomings of General Relativity and of the associated $$\varLambda $$ Λ CDM cosmological model. Recently, non-local theories of gravity have drawn increasing attention due to their potential to ameliorate both the ultraviolet and infrared behavior of gravitational interaction. In particular, Integral Kernel theories of Gravity provide a viable mechanism to explain the late time cosmic acceleration so as to avoid the introduction of any form of unknown dark energy. On the other hand, these models represent a natural link towards quantum gravity. Here, we study a scalar-tensor equivalent model of General Relativity corrected with non-local terms, where corrections are selected by the existence of Noether symmetries. After performing the weak field limit and generalizing the results to extended mass distributions, we analyse the non-local model at galaxy cluster scales, by comparing the theoretical predictions with gravitational lensing observations from the CLASH program. We obtain agreement with data at the same level of statistical significance as General Relativity. We also provide constraints for the Navarro–Frenk–White parameters and lower bounds for the non-local length scales. The results are finally compared with those from the literature.

Addressing Cosmological Tensions by Non-Local Gravity

“…However, another option is also available for the selection of the distortion function. In [57,140,141], a specific form of f (η) has been derived by exploiting the Noether symmetries [142] of a spherically symmetric background spacetime…”

“…Furthermore, several astrophysical tests have been performed on very different scales, and viable results turned out. In [141], the lensing properties of the galaxy clusters have been investigated in light of the exponential DW model, and a fully non-local regime with enhanced lensing strength has been highlighted. This feature clearly resembles the improved lensing response of the phenomenological form of the DW model, which is co-responsible for the lowered estimate of the σ 8 parameter.…”

“…The DW model has been tested on a wide range of astrophysical scales, from the galaxy clusters [141] to the stellar orbits around Sagittarius A* [140]. Most of the tests have been carried out for the exponential form of the non-local model, namely…”

“…A further test has been subsequently performed in [141], exploiting the CLASH lensing data from 19 massive clusters [147,148]. The point-mass potentials of Equations (6.2) and (6.3) were extended to a spherically symmetric mass distribution, i.e., the Navarro-Frenk-White density profile, and the non-local predictions for the lensing convergence were achieved.…”

Non-local gravity wormholes

“…The main features emerging in adopting non-local corrections in the gravitational action are the possibility to regularize and renormalize the theory at UV scales [71], the possibility to achieve accelerated cosmic expansion at IR scales [74,79,81], and, finally, the emergence of characteristic lengths, related to the auxiliary scalar fields, which could be useful to address large-scale structure [82], galactic systems [83], or high-energy phenomena [84].…”