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Astronomy and Space Physics

Erik Schildt (Uppsala University): Gravitational Waves in Bimetric Gravity (Master)



Student: Erik Schildt
Title: Gravitational Waves in Bimetric Gravity
Abstract: Understanding the cause of the accelerated expansion of the Universe is one of the most pressing issues in modern cosmology. An alternative to the Lambda-CDM-model is bimetric gravity which is an extension of Einstein's theory of general relativity. In bimetric gravity there exists both a massive and massless graviton which gives rise to different phenomenology in a number of sectors. The LIGO observations of gravitational waves from binary mergers has opened up a new sector to test this theory in. We study the effects of the massive mode on the observed gravitational waveform. We place constraints on the mass of the massive mode, and the mixing angle between the massless and massive mode by using: (i) the observed LIGO waveform for GW150916 compared with the bimetric waveform which includes gravitational wave oscillations, (ii) absence of gravitational echoes, (iii) constraints on the luminosity distance, and (iv) constraints on the propagation speed of gravity. We note that the effects of dispersion on the massive wave packet which we detect as the echo can distort the waveform noticeably, hence it is possible that LIGO cannot detect it. Further investigation in this area is necessary. 
Supervisor: Edvard Mörtsell, SU
Local supervisor: Martin Sahlén
Zoom: https://uu-se.zoom.us/j/66276500948