D6-branes and axion monodromy inflation

Journal of High Energy Physics 2016.3 (2016): 113 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)We develop new scenarios of large field inflation in type IIA string compactifications in which the key ingredient is a D6-brane that creates a potential for a B-field axion. The potential has the multi-branched structure typical of F-term axion monodromy models and, near its supersymmetric minima, it is described by a 4d supergravity model of chaotic inflation with a stabiliser field. The same statement applies to the D6-brane Wilson line, which can also be considered as an inflaton candidate. We analyse both cases in the context of type IIA moduli stabilisation, finding an effective potential for the inflaton system and a simple mechanism to lower the inflaton mass with respect to closed string moduli stabilised by fluxes. Finally, we compute the B-field potential for trans-Planckian field values by means of the DBI action. The effect of Planck suppressed corrections is a flattened potential which, in terms of the compactification parameters, interpolates between linear and quadratic inflation. This renders the cosmological parameters of these models compatible with current experimental bounds, with the tensor-to-scalar ratio ranging as 0.08 ≤ r ≤ 0.12This work has been partially supported by the grant FPA2012-32828 from the MINECO, the REA grant agreement PCIG10-GA-2011-304023 from the People Programme of FP7 (Marie Curie Action), the ERC Advanced Grant SPLE under contract ERC-2012-ADG-20120216-320421 and the grant SEV-2012-0249 of the “Centro de Excelencia Severo Ochoa” Programme. In additon D. E. and A.L. are respectively supported through the FPI grants SVP-2014-068283 and SVP-2013-067949, F.M. is supported by the Ramón y Cajal programme through the grant RYC-2009-05096 and D.R is supported by a grant from the Max Planck Societ