Mathematics

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Academic Profile

I am a Darby Fellow in Applied Mathematics and a researcher at Oxford Astrophysics. Before joining Lincoln, I was a member of Christ's College, University of Cambridge, where I studied Part III of the Mathematical Tripos at the Department of Applied Mathematics and Theoretical Physics. Subsequently, I joined the Institute of Astronomy, Cambridge, where I completed a Ph.D. in theoretical cosmology.

I am interested in the observational tests of theoretical ideas in cosmology.

Astronomical observations strongly suggest that a brief period of exponential expansion- so-called cosmological inflation- occurred in the very early Universe (a fraction of a second after its birth) at an extremely high energy. This is the simplest theory which could explain not only the near homogeneity of the cosmic microwave background across the sky, but also the origin and the distribution of galaxies and other large-scale structures. Although order-of-magnitude calculations of the predictions of inflation have been performed since the 80's, the next generation of satellites, telescopes and gravitational wave detectors will be able to measure inflationary observables to unprecedented precision. One of my research goals is to understand quantitatively what we will learn about the mathematical details of inflation from these ambitious observational projects.

Surprisingly, since the late 90's, observations of distant supernovae consistently suggest that the current expansion of the Universe is not slowing down (as most astronomers believed), but instead it is speeding up. The simplest theory stipulates that 70% of our Universe is filled with a form of Dark Energy sourced by Einstein's Cosmological Constant. However, the nature of Dark Energy is still very much a mystery, and an active area of research. My own investigation involves calculating the observable signatures of different Dark Energy models, and investigating whether the next  generation of Dark Energy experiments would be able to distinguish between them. I am also interested in how signatures of unexpected physics, such as the presence of extra dimensions or galactic-length cosmic strings, may be revealed by these ambitious Dark Energy experiments.

More details of my research and a list of publications can be found at  www-astro.physics.ox.ac.uk/~siri .