Emergence of Fresnel diffraction zones in gravitational lensing by a cosmic string
Abstract
The possibility to detect cosmic strings  topological defects of early Universe, by means of wave effects in gravitational lensing is discussed. To find the optimal observation conditions, we define the hyperbolicshaped Fresnel observation zones associated with the diffraction maxima and analyse the frequency patterns of wave amplification corresponding to different alignments. In particular, we show that diffraction of gravitational waves by the string may lead to significant amplification at cosmological distances. The wave properties we found are quite different from what one would expect, for instance, from light scattered off a thin wire or slit, since a cosmic string, as a topological defect, gives no shadow at all.
 Publication:

Physics Letters A
 Pub Date:
 June 2017
 DOI:
 10.1016/j.physleta.2017.03.046
 arXiv:
 arXiv:1612.07218
 Bibcode:
 2017PhLA..381.1764F
 Keywords:

 Cosmic strings;
 Topological defects;
 Gravitational lensing;
 Gravitational waves;
 Diffraction;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 Physics  Optics
 EPrint:
 11 pages, 9 figures