Gravity's weight on unification

Abstract

Much research in theoretical physics is inspired at least in part by the idea of unifying all of the fundamental forces of nature. An analysis of how gravity affects other forces at subnuclear scales has major implications for that idea. See Article In the standard model of particle physics, gravity is usually ignored as an irrelevance for most calculations of interest. But the possible effects of incorporating Einstein's theory of gravitation into the model have been a long-running topic of debate among theoretical physicists. In particular, a recent claim that the strength of the electric charge is affected by gravity has attracted great interest and controversy. David Toms reports a new calculation that confirms that combining quantum gravity with quantum electrodynamics — the part of quantum theory that deals with the interactions of electrons and photons — causes the strength of the electric charge to decrease to zero at high energies. The existence of this phenomenon, known as asymptotic freedom, supports the idea of a link between gravity and charge strength. In News and Views, Giovanni Amelino-Camelia discusses the possible implications of this result for the unification of the four fundamental forces.