I work in the field of theoretical cosmology and theories of gravity. Currently, I am exploring whether the large-scale phenomena commonly attributed to Dark Matter and Dark Energy may be explained by a new theory of gravity. This investigation includes generalized dark matter models, the Horndeski theory and k-mouflage based Modified Newtonian Dynamics. In addition to cosmology, I am interested in potential constraints on gravitational theories from solar-system, binary pulsars, Neutron stars and other strong field data and how these may relate to cosmological constraints. The goal is to develop methods adapted to testing theories which exhibit screening mechanisms.

In the past I worked on quintessence and its effects on the Cosmic Microwave Background, constraints on iso-curvature modes, Monte Carlo Markov Chain methods in cosmology, aspects of Bekenstein's Tensor-Vector-Scalar theory, the Eddington-Born-Infeld theory and its cosmology, the Brans-Dicke theory, and the rotation of CMB polarization spectrum due to massless pseudoscalars. More recently, I have pioneered model-independent methods for testing the theory of gravity on large scales.

I am the PI of the ERC funded “Theories and Models of the Dark Sector” (TheMoDS) project and the PI of the “Cosmology, Gravity and the Dark Sector of the Universe”(CoGraDS) project funded by the European Regional Development Fund and the state budget of the Czech Republic.