1202.1516 (Atsushi Naruko)

A general proof of the equivalence between the δN and covariant
formalisms    [PDF]

Atsushi Naruko

Recently, the equivalence between the \delta N and covariant formalisms has
been shown, but they assumed Einstein gravity in their proof [arXiv:1201.3163].
They showed that the evolution equation of the curvature covector in the
covariant formalism on uniform energy density slicings coincides with that of
the curvature perturbation in the \delta N formalism assuming the coincidence
of uniform energy and uniform expansion (Hubble) slicings, which is the case on
superhorizon scales in Einstein gravity. In this short note, we explicitly show
the equivalence between the \delta N and covariant formalisms without
specifying the slicing condition and the associated slicing coincidence, in
other words, regardless of the gravity theory.

View original: http://arxiv.org/abs/1202.1516