Racetrack inflation

We develop a model of eternal topological inflation using a racetrack potential within the context of type-IIB string theory with KKLT volume stabilization. The inflaton field is the imaginary part of the Kähler structure modulus, which is an axion-like field in the 4D effective field theory. This model does not require moving branes, and in this sense it is simpler than other models of string theory inflation. Contrary to single-exponential models, the structure of the potential in this example allows for the existence of saddle points between two degenerate local minima for which the slow-roll conditions can be satisfied in a particular range of parameter space. We conjecture that this type of inflation should be present in more general realizations of the modular landscape. We also consider 'irrational' models having a dense set of minima, and discuss their possible relevance for the cosmological constant problem. © SISSA/ISAS 2005.