Dr. Kumar Shwetketu Virbhadra – a native of Patna district in Bihar and a research associate professor at the University of Sciences in Philadelphia (USA)- has recently made a remarkable discovery in astrophysics. Dr. Virbhadra, as the leading (first) author, collaborated on this project with Dr. C. R. Keeton who is an assistant professor at Rutgers University in USA. Their discovery has shaken the prevailing notion that time delay of images formed due to gravitational lensing has to be always positive. Their paper ( Dr. K.S. Virbhadra and Dr. C.R. Keeton, Physical Review D, volume 77, year 2008) is recently published in a leading journal of the American Physical Society.
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It is well-known that deflection of light in gravitational field of a massive object can give rise to multiple images of the same source of light (such as a galaxy or a star). This spectacular phenomenon is called gravitational lensing. The presence of intervening massive objects (such as black holes, neutron stars, or galaxies), called gravitational lenses, magnify the images which are received in telescopes. For this reason, gravitational lensing phenomena are called nature-gifted Cosmic Telescopes. These help us probe even those parts of the Universe which were not otherwise accessible due to poor intensity of light. Though gravitational lensing magnifies images of light sources, it is known that it increases the travel time of light from a source to a telescope – and, the additional time is called time delay. Dr. Virbhadra and Dr. Keeton have recently proved that if a massive object is endowed with scalar field, the situation is surprisingly different. The presence of scalar field does not merely enhances the total magnification of images, but it also decreases the time delay, and therefore these will provide much better cosmic telescopes to humankind to be able to study the Universe more efficiently. Moreover, if the strength of scalar field is strong, the time delay could be, to a very great surprise, even negative. What does the negative time delay mean? It means that the time taken for light from a source to a telescope in presence of a massive object (close to travel path) is less than the time taken for the light if there were no intervening masses. There is no doubt that Dr. Virbhadra and Dr. Keeton’s remarkable discovery will have very important implications for cosmology research.
Dr. Virbhadra had made a few other very significant contributions in Einstein’s general theory of relativity and astrophysics. In past, he was also privileged to work and publish papers with Prof. Nathan Rosen (a principal collaborator of Albert Einstein to whom everyone knows) and Prof. G. F. R. Ellis (of Hawking-Ellis fame). Dr. Virbhadra is also known for having the largest number (five) papers on the list of top 50 highly cited papers during 2006 cited by papers in Einstein’s general relativity and quantum cosmology archive. For more information about him, please refer to the following URLs: