Synopsis: Wrestling with Infinities

Theorists show that mathematical divergences may not be a problem for the low-energy limit of certain effective theories of quantum gravity.
Synopsis figure
R. Akhoury et al., Phys. Rev. D (2011)

The absence of a consistent quantum theory of gravity continues to be the missing link between quantum mechanics and general relativity. One way to develop an effective theory of quantum gravity is to perturbatively quantize gravity, but this approach is known to create divergences (infinities) in the amplitudes that describe the scattering of gravitons—the particles that mediate gravity. There is, however, a useful mathematical connection between the structure of scattering amplitudes in perturbative quantum gravity and gauge theories of the standard model of particles. Theorists can therefore use a tool kit of methods developed for gauge theories to further develop perturbative quantum gravity.

In a paper appearing in Physical Review D, Ratindranath Akhoury at the University of Michigan in Ann Arbor and colleagues take advantage of this connection to investigate the so-called infrared divergences that appear at low energies in perturbative calculations of quantum gravity. Focusing on the scattering amplitudes of an arbitrary number of massless gravitons, they show that a class of divergencies (collinear divergencies) cancel at all orders in perturbation theory.

Ratindranath’s results shed light on the relationship between gauge theories and gravity. Viewed as results of an effective theory of quantum gravity, calculations of perturbative corrections to scattering amplitudes can be useful in gravitational phenomenology. – Alin Tirziu


More Announcements »

Subject Areas


Previous Synopsis

Next Synopsis

Particles and Fields

Coming off the Grid

Read More »

Related Articles

Synopsis: Skydiving Spins

Synopsis: Skydiving Spins

Atom interferometry shows that the free-fall acceleration of rubidium atoms of opposite spin orientation is the same to within 1 part in 10 million. Read More »

Focus: LIGO Bags Another Black Hole Merger

Focus: LIGO Bags Another Black Hole Merger

LIGO has detected a second burst of gravitational waves from merging black holes, suggesting that such detections will soon become routine and part of a new kind of astronomy. Read More »

Viewpoint: Paving the Way to Space-Based Gravitational-Wave Detectors

Viewpoint: Paving the Way to Space-Based Gravitational-Wave Detectors

The first results from the LISA Pathfinder mission demonstrate that two test masses can be put in free fall with a relative acceleration sufficiently free of noise to meet the requirements needed for space-based gravitational-wave detection. Read More »

More Articles