Dr M. C. David Marsh


  • 2015-date:  Stephen Hawking Advanced Fellow/Senior Research Associate, DAMTP, Cambridge.
  • 2012-2015: Postdoc, Rudolph Peierls Centre for Theoretical Physics, University of Oxford.
  • 2012:          Ph.D., Cornell University.
  • 2007:          M.Sc., Uppsala University.

For a more detailed CV, see my personal webpage (for the web-version) or send me an email (for the full version).  My publication list can be found at inspirehep.




Extreme astrophysical environments provide rare opportunities to test the fundamental laws of nature under conditions that go beyond the limitations of terrestrial laboratories. In my research, I develop the theory and phenomenology of well-motivated microphysical models. I then use these to identify and -- when relevant -- search for observational signals from new fundamental physics that may be imprinted on astronomical or cosmological observables. 


Astronomical axion searches


The axion is a hypothetical particle that first appeared as a solution to a puzzling problem in particle physics. Axions and the related "axion-like particles" (ALPs) appear frequently in extensions of the Standard Model of particle physics, including compactifications of string theory. Unfortunately, they are notoriously hard to detect. 


Astronomical observations provide exciting opportunities to search for axions and ALPs. I have previously demonstrated that X-ray observations of galaxy clusters have an unmatched sensitivity to light ALPs, and can be used to derive some of the strongest limits on their couplings. Upcoming X-ray satellite missions may shed light on the nature and couplings of dark matter, and the fundamental particle content of the universe. 


Early universe cosmology


The enormous energy density of the early, Big Bang universe provides a unique window to physics at scales not readily accessible through terrestrial experiments. I have previously invented theoretical techniques for studying new particles present in the early universe (in particular, during and after inflation), and for determining the imprints these may have left on cosmological observables such as the cosmic microwave background and the large-scale distribution of galaxies in the universe. 


Upcoming observations will study these observables with an unprecedented precision. My research aims to cease the opportunities these present to search for new fundamental physics from the early universe. 


String compactifications and cosmology


String theory is the leading candidate theory for ‘completing’ particle physics at very high energies, and is hypothetically connected to our four-dimensional spacetime by a compactification of additional spatial dimensions. The geometry of the tiny compactification manifold determines many of the properties of the theory at low energies, and can give rise to novel observational signals. 


I have previously investigated a number of aspects of string compactifications, including how these may explain the present accelerated expansion of the universe, and how novel mathematical techniques from random matrix theory can be used to confront the theoretical complexity of these theories.