Constraints on the Duration of Inflation from Entanglement Entropy Bounds

Using the fact that we only observe those modes exit Hubble horizon during inflation, one can calculate entanglement entropy of such long-wavelength perturbations by tracing out unobservable sub-Hubble fluctuations they are coupled with. On requiring this perturbative entropy, which increases with time, obey covariant bound for an accelerating background, find upper on duration inflation. This presents a new perspective (meta-)stability de Sitter spacetime and associated lifetime it.