Inflationary Perturbations in No-Scale Theories

Understand

We study the inflationary perturbations in general (classically) scale-invariant theories.

• Such scenario is motivated by the hierarchy problem and provides natural inflationary potentials and dark matter candidates.
• We analyse in detail all sectors (the scalar, vector and tensor perturbations) giving general formulae for the potentially observable power spectra, as well as for the curvature spectral index $n_s$ and the tensor-to-scalar ratio $r$.
• We show that the conserved Hamiltonian for all perturbations does not feature negative energies even in the presence of the Weyl-squared term if the appropriate quantization is performed and argue that this term does not lead to phenomenological problems at least in some relevant setups.