Semi-infinite slow contraction (ε>3) eliminates particle horizons, asymptotes to Minkowski in the past, remains geodesically complete and BGV-evading, and supplies stable low-entropy initial conditions after a non-singular bounce.
Nearly scale-invariant curvature modes from entropy perturbations during graceful exit
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abstract
In this Letter, we describe how a spectrum of entropic perturbations generated during a period of slow contraction can source a nearly scale-invariant spectrum of curvature perturbations on length scales larger than the Hubble radius during the transition from slow contraction to a classical non-singular bounce (the `graceful exit' phase). The sourcing occurs naturally through higher-order scalar field kinetic terms common to classical (non-singular) bounce mechanisms. We present a concrete example in which, by the end of the graceful exit phase, the initial entropic fluctuations have become negligible and the curvature fluctuations have a nearly scale-invariant spectrum with an amplitude consistent with observations.
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gr-qc 1years
2026 1verdicts
CONDITIONAL 1representative citing papers
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Causal Horizons, Geodesic Completeness and Stability in Slow Contraction Cosmology
Semi-infinite slow contraction (ε>3) eliminates particle horizons, asymptotes to Minkowski in the past, remains geodesically complete and BGV-evading, and supplies stable low-entropy initial conditions after a non-singular bounce.