Inflation in a scale invariant universe

Understand

A scale-invariant universe can have a period of accelerated expansion at early times: inflation.

• We use a frame-invariant approach to calculate inflationary observables in a scale invariant theory of gravity involving two scalar fields - the spectral indices, the tensor to scalar ratio, the level of isocurvature modes and non-Gaussianity.
• We show that scale symmetry leads to an exact cancellation of isocurvature modes and that, in the scale-symmetry broken phase, this theory is well described by a single scalar field theory.
• We find the predictions of this theory strongly compatible with current observations.