Primordial fluctuations and non-Gaussianities from multifield DBI Galileon inflation

Sébastien Renaux-Petel*, Shuntaro Mizuno, Kazuya Koyama

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)


We study a cosmological scenario in which the DBI action governing the motion of a D3-brane in a higher-dimensional spacetime is supplemented with an induced gravity term. The latter reduces to the quartic Galileon Lagrangian when the motion of the brane is non-relativistic and we show that it tends to violate the null energy condition and to render cosmological fluctuations ghosts. There nonetheless exists an interesting parameter space in which a stable phase of quasi-exponential expansion can be achieved while the induced gravity leaves non trivial imprints. We derive the exact second-order action governing the dynamics of linear perturbations and we show that it can be simply understood through a bimetric perspective. In the relativistic regime, we also calculate the dominant contribution to the primordial bispectrum and demonstrate that large non-Gaussianities of orthogonal shape can be generated, for the first time in a concrete model. More generally, we find that the sign and the shape of the bispectrum offer powerful diagnostics of the precise strength of the induced gravity.

Original languageEnglish
Article number042
JournalJournal of Cosmology and Astroparticle Physics
Issue number11
Publication statusPublished - 2011 Nov
Externally publishedYes


  • cosmological perturbation theory
  • in ation
  • modified gravity
  • non-gaussianity

ASJC Scopus subject areas

  • Astronomy and Astrophysics


Dive into the research topics of 'Primordial fluctuations and non-Gaussianities from multifield DBI Galileon inflation'. Together they form a unique fingerprint.

Cite this