My research aims at understanding the Big Bang: by studying the very early Universe we can test fundamental theories of physics, and trace the history of the first few instants of time.

Key moments in the history of the universe are at phase transitions, where the state of matter changes, and fundamental symmetries of nature are hidden (or "broken"). We can learn about phase transitions from the relics they leave behind: including extended long-lived structures called topological defects, and gravitational waves.

I am currently working intensively on gravitational waves from the electroweak phase transition, when the Higgs field turned on and gave other elementary particles their masses. This could have been a violent event: the whole Universe may have started to bubble at around 10 picoseconds old, emitting gravitational waves at a frequency detectable at the future space-based detector LISA. I am a member of the LISA Consortium, responsible for calculating the expected signals from phase transitions.

Much of my research uses large numerical simulations of processes in the early universe. Here's one from the Cosmic Defects YouTube channel, showing a visualisation of the Higgs field turning on at around 10 picoseconds after the beginning of the Universe. The coloured rings are slices through spherical compression waves surrounding the expanding bubbles of Higgs field. The video was made by my collaborator David Weir (University of Helsinki).