Phil Bull > Research


My area of expertise is in theoretical cosmology and general relativity. I'm fascinated by the lumpy, inhomogeneous nature of the Universe that we live in, and how structures evolve and interact on large scales. One of the biggest puzzles in this area is the (relatively) recent finding that the expansion of the Universe appears to be accelerating. This is a very curious result, and I'd like to get to the bottom of it!


There are many different approaches that can be taken to study the apparent acceleration. I'm particularly interested in the effects of inhomogeneities on cosmological observations, and testing the assumptions that go into building cosmological models. Is General Relativity the correct theory of gravity? How do inhomogeneities distort light from the distant objects that we observe when measuring the acceleration? What's the best way of constructing a cosmological model from observations of the real, complicated, inhomogeneous Universe? By answering these questions, we can strengthen the foundations of modern cosmology, and gain valuable insights into the nature of the cosmic acceleration.

I'm also interested in the interaction between theory and observation. We are continually discovering exciting new ways of measuring the cosmos, so it's important to develop methods to exploit these data in interesting ways. Two particularly promising classes of observables are intensity mapping with the neutral hydrogen 21cm emission line, and secondary anisotropies of the CMB, which include the thermal and kinematic Sunyaev-Zel'dovich effects and blackbody spectral distortions. Their potential as cosmological probes will be realised in the near future as more sensitive radio and CMB experiments like the SKA and Advanced ACTPol start delivering data, so it's important to build up our theoretical understanding of them right now.

Research Interests

My technical interests are quite broad, and include:



Recent Collaborators

My DPhil (PhD) was supervised by Pedro Ferreira in Oxford, and Tim Clifton, now at Queen Mary University of London.