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GRG Editor's Choice: Gravitational lensing beyond geometric optics – I. Formalism and observables

Harte, A.I., Gravitational lensing beyond geometric optics: I. Formalism and observables, Gen Relativ Gravit (2019) 51: 14.

Editor's Choice (Research Article)

First Online: 03 January 2019

"The author discusses three types of wave equations (scalar, Maxwell and gravitational) on a curved background in the WKB approximation. While many papers already discuss this problem, the author's approach is very comprehensive, with an excellent and detailed introduction on the WKB method and the discussion of its limitations, as well as a review of the previous papers on the topic. All derivations are thorough and many results seem to be new. The comparison between the scalar, vector and tensor wave equation is very interesting."


The laws of geometric optics and their corrections are derived for scalar, electromagnetic, and gravitational waves propagating in generic curved spacetimes. Local peeling-type results are obtained, where different components of high-frequency fields are shown to scale with different powers of their frequencies. Additionally, finite-frequency corrections are identified for a number of conservation laws and observables. Among these observables are a field’s energy and momentum densities, as well as several candidates for its corrected “propagation directions”.

The author: 

harte © harteAbraham Harte is Assistant Professor in the School of Mathematical Sciences at Dublin City University, Ireland. He research interests are general relativity and gravitational physics: theory of motion (self-force and extended-body effects), wave propagation in curved spacetimes, gravitational lensing, and gravitational waves.

GRG Editor's Choice:

In each volume of GRG, a few papers are marked as “Editor’s Choice”. The primary criteria is original, high quality research that is of wide interest within the community.