Cosmology and Fundamental physics

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Research interests in Cosmology and Fundamental Physics at the Institute of Astronomy cover a wide array of physical phenomena, spanning a large range of astrophysical scales and epochs - from the present day properties of the Universe going back in time to the surface of last scattering and the Planck scale era.

In order to study these complex and non-linear physical phenomena with the highest possible realism, researchers are using sophisticated numerical codes and taking advantage of high performance super-computer facilities available locally, such as the Cambridge Service for Data-Driven Discovery (CSD3), one of the largest academic supercomputers in the UK.

Cosmic Microwave Background

A major effort is underway to learn about the origin and evolution of the universe from observations of the cosmic microwave background (CMB) - the faint afterglow of the big bang. Observations of tiny fluctuations in this radiation may be able to give powerful constraints on theories of the early universe (for example the popular inflation model), and indirectly constrain physics at much higher energies than can be measured directly in the laboratory. Members of the IoA work on both theoretical predictions for the expected signals and the details of how to analyse data from forthcoming observations.

Cosmic Reionisation

In the framework of the hot big bang model, our Universe is expected to become almost neutral around 400,000 years after the big bang. On the other hand, we know from observations of quasar absorption spectra that the same Universe has become highly ionized by the time it is one Gigayear old. The reionization of the Universe is driven by radiation from first luminous sources (galaxies/stars). Studying reionization will thus tell us how the first galaxies formed and what they looked like.

Gravitational Waves

Physics beyond the standard model

One of the most remarkable astrophysical findings over the last century is the result that baryonic matter only comprises around 5% of the mass/energy density of the Universe. The remaining 95% is made up of dark matter (~25% of the total), and dark energy ( ~70% of the total). Researches at the IoA use a variety of observational and theoretical techniques to try to better understand these mysterious issues. Large cosmological datasets (such as the Dark Energy Survey) provide information about the structure of the nearby Universe, which can be used to test models of both dark matter and dark energy. 

Supernova cosmology

Type Ia supernovae are some of the brightest and most homogeneous explosions in the night sky. They have been used as excellent distance indicators both in the discovery of accelerated expansion, driven by dark energy and the measurement of the Hubble Constant. Members of the IoA are developing new methods for cosmological inference using accurate distance indicators, wide-field surveys of the transient sky and advanced Bayesian modelling of line of sight effects like extinction by dust. We also work on the new frontier of strongly gravitationally lensed transients, for studying the explosion mechanism in the high-redshift universe and as a new path to measuring the Hubble Constant with time-delay distances.