Inflating without a flat potential: Viscous inflation

TL;DR

This paper proposes a novel inflationary model driven by bulk viscosity instead of a flat potential, where viscous effects induce negative pressure and sustain inflation.

Contribution

It introduces a viscous inflation model where slow-roll is achieved through viscosity, not potential flatness, offering an alternative mechanism for inflation.

Findings

Power spectrum is nearly scale-invariant

Hubble rate depends only on inflaton kinetic energy

Tilt of spectrum linked to model's slow-roll parameters

Abstract

Bulk viscosity leads to negative pressure, which is a key ingredient for successful inflation. We build an inflationary model where the slow-roll of the inflaton field is driven by a viscous component instead of the flat potential commonly used. Since viscosity does not contribute to the energy density of the Universe, the Hubble rate depends only on the kinetic energy of the inflaton. The power spectrum is almost scale-invariant, with a tilt depending on the slow-roll parameters defined within the model.