My research focuses on astrophysical tests of modified gravity theories such as the chameleon and symmetron models. These theories allow for large deviations from Einstein's theory of General Relativity on large scales whilst screening out the modifications in our own solar system such that local bounds on modified gravity and the weak equivalence principle are satisfied.
My research has focused on the properties of stars in these theories, which may be unscreened and show novel effects in under-dense dwarf galaxies situated in cosmic voids. I have a computer code that can simulate the structure and evolution of stars in these theories with enough precision to allow a comparison with data. I also have a separate code that can calculate the new pulsation properties of these stars.
By comparing the inferred distances to unscreened dwarf galaxies measured using Cepheid and Tip of the Red Giant Branch stars my collaborators at UPenn and I were able to place new constraints on these theories. These are currently the strongest constraints in the literature.
A video of one of my talks on this subject can be found in the seminars section below.
I have also worked on supersymmetric models of modified gravity and have established a no-go theorem precluding the existence of supersymmetric symmetrons and rendering most other chameleon-like screening mechanisms observationally undetectable.