When matter matters

Damien Easson, Ignacy Sawicki, Alexander Vikman

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


We study a recently proposed scenario for the early universe: Subluminal Galilean Genesis. We prove that without any other matter present in the spatially flat Friedmann universe, the perturbations of the Galileon scalar field propagate with a speed at most equal to the speed of light. This proof applies to all cosmological solutions - to the whole phase space. However, in a more realistic situation, when one includes any matter which is not directly coupled to the Galileon, there always exists a region of phase space where these perturbations propagate superluminally, indeed with arbitrarily high speed. We illustrate our analytic proof with numerical computations. We discuss the implications of this result for the possible UV completion of the model.

Original languageEnglish (US)
Article number014
JournalJournal of Cosmology and Astroparticle Physics
Issue number7
StatePublished - Jul 2013


  • Alternatives to inflation
  • Cosmic singularity
  • Cosmological perturbation theory
  • Initial conditions and eternal universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics


Dive into the research topics of 'When matter matters'. Together they form a unique fingerprint.

Cite this