Constraints on the duration of inflation from entanglement entropy bounds

Abstract

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

String Cosmology and the Breakdown of Local Effective Field Theory

“…A third way of justifying the TCC condition ( 4) is by studying the entanglement entropy between sub-and super-Hubble modes induced by the leading nonlinearities (the pure entanglement entropy due to squeezing of the super-Hubble modes was already considered in [31]). In the case of inflationary cosmology, demanding that the entanglement entropy not exceed the thermal entropy after inflation [32] or the Gibbons-Hawking entropy of a de Sitter phase [33] yields an upper bound on the number of e-foldings which, up to a numerical factor, agrees with (5). This analysis is closely related to work which shows that de Sitter space is a "fast scrambler" (see e.g.…”

Quantum corrections to the primordial tensor spectrum: open EFTs & Markovian decoupling of UV modes

“…8 However, if it is found that non-Markovian effects are small for observable modes and can yet become large for another subset of modes of the system, these would lead to deep ramifications for inflation (e.g. for eternal inflation) [66] and even for QFT in dS spacetimes (e.g. for the lifetime of metastable dS) [67][68][69].…”