Roya Mohayaee

I am a professor of astrophysics at the Institut d'Astrophysique de Paris of Sorbonne University and will be at the department of theoretical Physics at Oxford University for the academic year of 2022-2023 during my sabbatical year.

My research projects is focused on two themes:

(1) Interdisciplinary research on the application of optimal transport theory to astrophysics.

(2) Test of the cosmological principle 

Optimal Transport theory (OT) is a beautiful branch of mathematics which has recently found applications in divers areas of science, from biology and fluid mechanics to economics and machine learning. The theory allows us to find an optimal mapping between two different probability distribution functions. I have been working in collaboration with mathematicians, physicists and computer scientists on the applications of this theory to the problematics in astrophysics. We have shown that the past history of the Universe can be reconstructed using OT, which also allows an efficient retrieval of the velocity field of galaxies (a hard observational task). We can test Einstein's theory of general relativity through OT, by the accurate reconstruction of the baryonic acoustic oscillations. In a recent collaboration, we have developed new algorithm suitable for large astrophysical datasets. Our latest algorithm and results have just been published in PRL (see : von Hausegger, Lévy, Mohayaee, 2022, Accurate Baryon Acoustic Oscillations reconstruction bias semi discrete Optimal Transport) , Volume 128, Issue 20, article id.201302). 

I am also organising a school in the French Alps at école Physique des Houches, 13-17 March 2022, on optimal Transport Theory : applications to Physics. Here is the web page:  opti-phy.sciencesconf.org; Join us !

The cosmological principle (CP) assumes that the Universe is homogeneous and isotropic statistically on large scales. This assumption is widely used in handling cosmological data and in deducing various parameters. Friedmann-Lemaître-Robertson-Walker (FLRW) metric which is the founding block of the standard model of cosmology (namely Lambda-CDM) assumes CP. My research focuses on observational verifications of this principle. In a decade-long collaboration with my host at Oxford, Prof Subir Sarkar, we have been looking into distant Universe to test CP. Our recent results on high-redshift infra-red quasars and radio galaxies, both published in astrophysical journal letters, show otherwise. It seems that CP is violated and our distant Universe is not simply spherically symmetric, isotropic and homogeneous. (see  A challenge to the standard Cosmological Model, to appear in ApJLetters, and also  A test of the cosmological principle with quasars, (2021ApJ...908L..51S)). Our recent works  has been  featured on the front page of the physics department.