Trans-Planckian Censorship and $k$-inflation

Abstract

We propose a more general version of the Trans-Planckian Censorship Conjecture (TCC) which can apply to models of inflation with varying speed of sound. We find that inflation models with $c_S<1$ are in general more strongly constrained by censorship of trans-Planckian modes than canonical inflation models, with the upper bound on the tensor/scalar ratio reduced by as much as three orders of magnitude for sound speeds consistent with bounds from data. In particular, models which satisfy the TCC, and therefore the de Sitter Swampland Conjecture, can still violate the more general condition for non-classicality of trans-Planckian modes. As a concrete example, we apply the constraint to Dirac-Born-Infeld inflation models motivated by string theory.

arXiv comment9 pages, 4 figures. (V3: The version accepted by PRD. With a major revision and figures replaced.)

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• Brane inflation and Trans-Planckian censorship conjecture
• Spectrum of Cuscuton Bounce
• Reconstructing k-essence: Unifying the attractor $n_S(N)$ and the swampland criteria
• Non-canonical kinetic structures in the swampland
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• Generalizing the Swampland: Embedding $P(X,\phi )$ Inflationary Theories in a Curved Multi-field Space
• The Trans-Planckian problem in Tachyacoustic Cosmology
• Escape from the swamp with spectator
• Trans-Planckian Censorship Conjecture and Early Universe Cosmology
• Implications of single field inflation in general cosmological scenarios on the nature of dark energy given the swampland conjectures