Non-Gaussianity in braneworld and tachyon inflation

Abstract

We calculate the bispectrum of single-field braneworld inflation, triggered by either an ordinary scalar field or a cosmological tachyon, by means of a gradient expansion of large-scale non-linear perturbations coupled to stochastic dynamics. The resulting effect is identical to that for single-field 4D standard inflation, the non-linearity parameter being proportional to the scalar spectral index in the limit of collapsing momentum. If the slow-roll approximation is assumed, braneworld and tachyon non-Gaussianities are subdominant with respect to the post-inflationary contribution. However, bulk physics may considerably strengthen the non-linear signatures. These features do not change significantly when considered in a non-commutative framework.

17 pages; v2: added references and previously skipped details in the derivation of the result; v3: improved discussion

References in corpus (3)

• Observational constraints on patch inflation in noncommutative spacetime
• Seed perturbations for primordial magnetic fields from MSSM flat directions
• Consistency relations and degeneracies in (non)commutative patch inflation

Cited by in corpus (1)

• Cosmological constraints on string scale and coupling arising from tachyonic instability