2023
07/21
OPEN
Date
2023/07/21（Fri）15:00〜16:00
Venue
Hybrid : Kenkyu-Honkan Room303, Online(Zoom)
Speaker
Prof. Teruaki Suyama (Titech)
Language
English
URL
Contact
Asuka Ito / asuka.ito-AT-kek.jp
Overview
Gravitational lensing (GL) has been a powerful method to probe matter inhomogeneities in the Universe. GL of gravitational waves, which will be detected in the near future, will enable us to gain more information of the nature of dark matter and further boost the significance of GL. In light of this situation, it is important to have understanding of basic properties of GL. In my talk, I show that gravitational lensing obeys the causality in the sense that (electromagnetic/gravitational) waves emitted from the source arrive at an observer only after the arrival of the signal in geometrical optics. This leads to the Kramers-Kronig relation, a well-known relation in the field of optics, in GL, as the relation between real and imaginary parts of the amplification factor. I will also show some relations which hold as consequence of the Kramers-Kronig relation. Finally, I argue that examining the violation of the Kramers-Kronig relation may be used for correctly extracting the lensing signal in the gravitational wave observations.