Abstract
We propose a mechanism borrowed from string theory which yields a nonsingular transition from a phase of ekpyrotic contraction to the expanding phase of standard big bang cosmology. The same mechanism converts the initial vacuum spectrum of cosmological fluctuations before the bounce into a scale-invariant one, and also changes the spectrum of gravitational waves into an almost scale-invariant one. The scalar and tensor tilts are predicted to be the same, in contrast to the predictions from the “string gas cosmology” scenario. The amplitude of the gravitational wave spectrum depends on the ratio of the string scale to the Planck scale and may be in reach of upcoming experiments.
- Received 6 February 2020
- Accepted 3 March 2020
DOI:https://doi.org/10.1103/PhysRevD.101.063522
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society