Non-relativistic matrix inflation

We reconsider a string theoretic inflationary model, where inflation is driven by n multiple coincident D3-branes in the finite n limit. We show that the finite n action can be continued to the limit of large n, where it converges to the action for a wrapped D5-brane with n units of U(1) flux. This provides an important consistency check of the scenario and allows for more control over certain back-reaction effects. We determine the most general form of the action for a specific sub-class of models and examine the non-relativistic limits of the theory where the branes move at speeds much less than the speed of light. The non-Abelian nature of the world-volume theory implies that the inflaton field is matrix valued and this results in modifications to the slow-roll parameters and Hubble-flow equations. A specific model of inflation is investigated where the branes move out of an AdS throat, and observational constraints are employed to place bounds on the background fluxes.