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Paper IPM / Astronomy / 14571  


Abstract:  
Stochastic effects in multifield inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary efolds. Solving the resulting partial differential equations in multidimensional field space is more challenging than the singlefield case. A few tractable examples are discussed, which show that the number of fields is, in general, a critical parameter. When more than two fields are present for instance, the probability to explore arbitrarily largefield regions of the potential, otherwise inaccessible to singlefield dynamics, becomes nonzero. In some configurations, this gives rise to an infinite mean number of efolds, regardless of the initial conditions. Another difference with respect to singlefield scenarios is that multifield stochastic effects can be large even at subPlanckian energy. This opens interesting new possibilities for probing quantum effects in inflationary dynamics, since the moments of the numbers of efolds can be used to calculate the distribution of primordial density perturbations in the stochasticÃÂ´N formalism.
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