On the fate of coupled flat directions during inflation

Understand

We investigate the stochastic dynamics of the long wavelength modes of a generic light scalar field that during inflation is coupled to another scalar field.

• The coupling plays an important role for the fluctuation of the field amplitude and may block its initial growth.
• We find that such a blocking is avoided, albeit only temporarily, if the light scalar has an initial non-vanishing expectation value <\phi> larger than a certain critical value, for which we provide an estimate.
• We also show that the field fluctuations will eventually reach an equilibrium amplitude provided inflation is sufficiently long-lasting.