Theoretical implications of detecting gravitational waves

Understand

This paper is the third in a series of theorems which state how cosmological observations can provide evidence for an early phase of acceleration in the universe.

• Previous theorems demonstrated that the observed power spectrum for scalar perturbations forces all possible alternative theories of inflation to theories other than General Relativity.
• It was shown that generically, without a phase of accelerated expansion, these alternatives have to break at least one of the following tenets of classical general relativity: the Null Energy Condition (NEC), subluminal signal propagation, or sub-Planckian energy densities.
• In this paper we prove how detection of primordial gravitational waves at large scales can provide independent evidence to support a phase of accelerated expansion.