# LATEST RESEARCH ON GRAVITY: FEB. – 2020

*Massive Gravity*

We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alternative and related models of massive gravity such as new massive gravity, Lorentz-violating massive gravity and non-local massive gravity. [1]

*Analogue Gravity*

Analogue gravity is a research programme which investigates analogues of general relativistic gravitational fields within other physical systems, typically but not exclusively condensed matter systems, with the aim of gaining new insights into their corresponding problems. Analogue models of (and for) gravity have a long and distinguished history dating back to the earliest years of general relativity. [2]

*Extended Theories of Gravity*

*Extended Theories of Gravity*

Extended Theories of Gravity can be considered as a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein’s theory, is aimed to address conceptual and experimental problems recently emerged in astrophysics, cosmology and High Energy Physics. In particular, the goal is to encompass, in a self-consistent scheme, problems like inflation, dark energy, dark matter, large scale structure and, first of all, to give at least an effective description of Quantum Gravity. [3]

*Entropic Uncertainty Relations, Entanglement and Quantum Gravity Effects via the Generalised Uncertainty Principle*

We apply the generalised uncertainty principle (GUP) to the entropic uncertainty relation conditions on quantum entanglement. In particular, we study the GUP corrections to the Shannon entropic uncertainty condition for entanglement. [4]

*Electro-Gravity via Geometric Chronon Field*

Aim: To develop a model of matter that will account for electro-gravity. Interacting particles with non-gravitational fields can be seen as clocks whose trajectory is not Minkowsky geodesic. A field, in which each such small enough clock is not geodesic, can be described by a scalar field of time, whose gradient has non-zero curvature. This way the scalar field adds information to space-time, which is not anticipated by the metric tensor alone. The scalar field can’t be realized as a coordinate because it can be measured from a reference sub-manifold along different curves. [5]

Reference

[1] de Rham, C., 2014. Massive gravity. *Living reviews in relativity*, *17*(1), p.7.

[2] Barceló, C., Liberati, S. and Visser, M., 2011. Analogue gravity. *Living reviews in relativity*, *14*(1), p.3.

[3] Capozziello, S. and De Laurentis, M., 2011. Extended theories of gravity. *Physics Reports*, *509*(4-5), pp.167-321.

[4] Gadea, O. and Blado, G., 2018. Entropic Uncertainty Relations, Entanglement and Quantum Gravity Effects via the Generalised Uncertainty Principle. *Asian Journal of Research and Reviews in Physics*, pp.1-12.

[5] Suchard, E.H., 2017, May. Electro-gravity via geometric chrononfield. In *Journal of Physics: Conference Series* (Vol. 845, No. 1, p. 012019). IOP Publishing.