Multi-disformal invariance of non-linear primordial perturbations

Yuki Watanabe, Atsushi Naruko, Misao Sasaki

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


We study disformal transformations of the metric in the cosmological context. We first consider the disformal transformation generated by a scalar field φ and show that the curvature and tensor perturbations on the uniform φ slicing, on which the scalar field is homogeneous, are non-linearly invariant under the disformal transformation. Then we discuss the transformation properties of the evolution equations for the curvature and tensor perturbations at full non-linear order in the context of spatial gradient expansion as well as at linear order. In particular, we show that the transformation can be described in two different ways: one that clearly shows the physical invariance and the other that shows an apparent change of the causal structure. Finally we consider a new type of disformal transformation in which a multi-component scalar field comes into play, which we call a "multi-disformal transformation". We show that the curvature and tensor perturbations are invariant at linear order, and also at non-linear order, provided that the system has reached the adiabatic limit.

Original languageEnglish
Article number39002
Issue number3
Publication statusPublished - 2015 Aug 1
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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