Do we really live in four or in higher dimensions?

by Dadhich Naresh (M.A. Chair in Theoretical Physics, Jamia Millia Islamia, Delhi and Inter-University Center for Astronomy & Astrophysics (IUCAA) Pune, India)

Monday 30 May 2016, 14:30 → 16:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

In Einstein gravity, gravitational potential goes as 1/rd−3 in d spacetime dimensions, which assumes the familiar 1/r form in four dimensions. On the other hand, it goes as 1/rα with α = (d−2N−1)/m in pure Lovelock gravity involving only one Nth order term of the Lovelock polynomial in the gravitational action. The latter offers a novel possibility of having 1/r potential for the dimension spectrum given by d = 3N + 1. Thus it turns out that in the two prototype gravitational settings of isolated objects like black holes and the universe as a whole – cosmological models, there is no way to distinguish between Einstein in four and Nth order pure Lovelock in 3N+1 dimensions, i.e., in particular N = 1 four dimensional Einstein and N = 2 seven dimensional pure Gauss-Bonnet gravity. As envisaged in higher dimensional theory, all matter fields, e.g., electromagnetic field, remain confined to the usual four dimensions while gravity is however free to propagate in higher dimensions. But it cannot distinguish between any two members of the dimension spectrum, then one wonders, do we really live in four or in higher dimensions?