Quantum gravitational contributions to quantum electrodynamics

• Published in: Nature (London) 2010-11, Vol.468 (7320), p.56-59
• Main Author: Toms, David J
• Format: Article
• Language: English
• Subjects: 639/766/483/1139; Asymptotic properties; Charge; Electric charge; Gravitation; Humanities and Social Sciences; Mathematical models; multidisciplinary; Photons; Quantum electrodynamics; Quantum gravity; Relativity; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature09506

Quantum electrodynamics describes the interactions of electrons and photons. Electric charge (the gauge coupling constant) is energy dependent, and there is a previous claim that charge is affected by gravity (described by general relativity) with the implication that the charge is reduced at high energies. However, that claim has been very controversial and the matter has not been settled. Here I report an analysis (free from the earlier controversies) demonstrating that quantum gravity corrections to quantum electrodynamics have a quadratic energy dependence that result in the electric charge vanishing at high energies, a result known as asymptotic freedom. Quantum gravity: no charge at high energies? 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. Within quantum electrodynamics electric charge is energy dependent, and there is a previous claim that charge is affected by gravity (general relativity) with the implication that the charge is reduced at high energies. But that claim has been very controversial. This author reports an analysis demonstrating that quantum gravity corrections to quantum electrodynamics have a quadratic energy dependence that results in the electric charge vanishing at high energies.