### Research: early Universe cosmology

Early Universe cosmology is the study of the first few seconds of the Universe's evolution. It involves finding particle physics based models which explain the observed properties of the present day Universe.

Inflation is a period of accelerated expansion proposed to have occurred in the early Universe. It resolves various short-comings of the standard big bang model and also provides a mechanism for generating the primordial perturbations from which structure forms. Observational measurements of the spectrum of the primordial perturbations, from large scale structure and the cosmic microwave background, therefore constrain inflation models and high energy physics.

I have a long standing interest in Primordial Black Holes (PBHs) as a probe of the physics of the early Universe. Gravitational effects as well as the consequences of their evaporation via Hawking radiation, place tight limits on the number of PBHs which can form. These limits can be translated into constraints on the primordial density perturbations on small scales, which can in turn be used to constrain models of inflation. Recently I’ve shown that microlensing and dynamical constraints together exclude multi-solar mass PBHs as a dark matter candidate.