Gravitational waves in vector inflation

Understand

We discuss the gravitational waves (GW) in the context of vector inflation.

• We derive the action for tensor perturbations and find that tachyonic instabilities are present in most (but not all) of the inflationary models with large fields.
• In contrast, the stability of the small field inflation ($A_{\mu}A^{\mu}\ll\frac{1}{N}$) is ensured by the usual slow-roll conditions, where $N$ is the total number of fields.
• For example, the Coleman-Weinberg potential and the power-law inflation are always stable in the small fields limit with an approximately flat spectrum of GW.