Warped Wilson Line DBI Inflation

TL;DR

Warped Wilson Line DBI inflation investigates inflaton dynamics when Wilson line moduli on a Dp-brane, rather than brane position, drive DBI-like inflation in warped flux compactifications. By deriving the full DBI+WZ action and reducing to a four-dimensional effective theory, the authors show mixing between Wilson line and position fields and formulate canonical normalizations that depend on warp factors and fluxes. Using a Hamilton-Jacobi framework, they compute perturbation spectra and establish both upper and lower bounds on the tensor-to-scalar ratio $r$, finding a viable parameter region in which sizeable non-Gaussianity characterized by $f_{NL}$ and observable gravitational waves can coexist. The work highlights a promising string-motivated route to detectable $r$ and $f_{NL}$, while emphasizing the need for explicit geometric embeddings and potential extensions to multifield setups to fully assess viability and backreaction constraints.

Abstract

We propose a novel inflationary scenario in string theory in which the inflaton field is a 'Wilson line' degree of freedom in the worldvolume of a probe Dp-brane, in a warped flux compactification. Kinetic terms for Wilson line fields on the world volume of a D-brane take a nonstandard Dirac-Born-Infeld (DBI) form. Thus, we work in the framework of DBI inflation. This extends the original slow roll Wilson line inflationary scenario, where only the quadratic piece was considered. Warped DBI Wilson line inflation offers an attractive alternative to ordinary (position field) DBI inflation, inasmuch as observational and theoretical constraints get considerably relaxed. Besides the standard large non-Gaussianities in DBI scenarios, it is also possible to achieve an observable amount of gravitational waves.