Causality and cosmic inflation

Tanmay Vachaspati, Mark Trodden

Research output: Contribution to journalArticlepeer-review

121 Scopus citations


In the context of inflationary models with a pre-inflationary stage, in which the Einstein equations are obeyed, the null energy condition is satisfied, and spacetime topology is trivial, we argue that homogeneity on super-Hubble scales must be assumed as an initial condition. Models in which inflation arises from field dynamics in a Friedmann-Robertson-Walker background fall into this class but models in which inflation originates at the Planck epoch may evade this conclusion. Our arguments rest on causality and general relativistic constraints on the structure of spacetime. We discuss modifications to existing scenarios that may avoid the need for initial large-scale homogeneity.

Original languageEnglish (US)
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number2
StatePublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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