Galilean field gravitational lensing



I was the first to point out that the galilean-invariant scalar field that emerges in massive gravity can enhance gravitational lensing; other popular scalar-tensor gravity theories have no new lensing effects. I am now studying how to detect or constrain this novel effect.

The Gelaton Scenario



The distinctive features of single field inflationary models with non-minimal kinetic terms, like Dirac-Born-Infeld and k-inflation, can be captured by more familiar multiple field inflationary systems. At least one heavy field, which we call the gelaton, has an effective potential which depends on the kinetic energy of the inflaton. Integrating out the gelaton gives rise to an effectively single field system for which the speed of sound for the adiabatic fluctuations is reduced, generating potentially observable equilateral non-Gaussianity, while causing negligible isocurvature fluctuations.

Structure formation in massive gravity



I study a phenomenologically viable modification of gravity with a massive graviton. My work is concerned with how large scale structure develops in this model. I am using N-body, particle-mesh codes to study this. I have used galaxy survey data and other cosmological observations to place limits on the model parameters. Current observations of bulk flows may hint at the kind of new physics found in these models.

Stochastic Inflation Revisited



Stochastic inflation is the study of the global inflationary space, where quantum perturbations grow to horizon size and affect the overall progress of inflation. It is the best way to study eternal inflation and to understand the global structure of inflationary models. I have generalized this formalism to theories of inflation with non-standard kinetic energy terms, like DBI inflation.

Cosmic superstrings



I am continuing to study the distinctive phenomenology of cosmic superstrings. Their contributions to the small angular scale power and B-mode polarization of the CMB could be seen within the next couple of years. In the meantime, I have worked out one of their effects on the 21 cm radiation that will eventually be the richest resource for observational data.

Primordial magnetism and 21 cm radiation



I have proposed one (fairly farfetched) theory of how today's galactic magnetic fields got their start. New observations are beginning to reveal, though, that large galactic magnetic fields have existed since the Universe was half its age. I'm exploring what this means for magnetic field generation.