Universality Classes of Scale Invariant Inflation

Abstract

We investigate the inflationary implications of extensions of Poincare symmetry. The simplest constructions with local scale invariance lead to universal predictions: the spectral index is $n_s=1-2/N$, in excellent agreement with Planck data, while the tensor-to-scalar ratio is determined by a free parameter to $r=12\alpha /N^2$. For the special value $\alpha =1$ one finds symmetry enhancement to the full conformal group. We show that these findings hold both for two-derivative scalar-tensor theories as well as higher-derivative gravity. Therefore scale invariance underlies a promising set of inflationary models.

6 pages, 1 figure

References in corpus (4)

• The Unity of Cosmological Attractors
• Fake Conformal Symmetry in Conformal Cosmological Models
• Inflation from Broken Scale Invariance
• Gauge Natural Formulation of Conformal Theory of Gravity