TY - JOUR
T1 - Sourced fluctuations in generic slow contraction
AU - Artymowski, Micha
AU - Ben-Dayan, Ido
AU - Thattarampilly, Udaykrishna
N1 - Publisher Copyright:
© 2021 IOP Publishing Ltd and Sissa Medialab.
PY - 2021/6
Y1 - 2021/6
N2 - We introduce a set of generic conditions for the slow contracting Universe and for a narrowed-down category of models called fast-roll models. We present general conditions for superhorizon freeze-out of scalar and tensor perturbations and show that any fast-roll model satisfies them, as in the case of inflation. We are interested in the "Sourced Bounce"scenario, where perturbations are sourced by a U(1) gauge field coupled to a bouncer scalar field. The requirement of a slightly red tilted scalar spectrum greatly restricts the allowed couplings between the scalar and the gauge field. We show that a viable slightly red scalar spectrum is achievable. However, within the fast-roll approximation the tensor-to-scalar ratio is in general r ≃ 1/9, inconsistent with current observations. We demonstrate the general result with an explicit example we dub "Intermediate contraction". We prove that small modifications in fast-roll that do not alter the Green's functions, do not result in r < 0.06 consistent with the data for more than an e-fold. Hence, a successful "Sourced Bounce"requires a different source or a significant deviation from fast-roll.
AB - We introduce a set of generic conditions for the slow contracting Universe and for a narrowed-down category of models called fast-roll models. We present general conditions for superhorizon freeze-out of scalar and tensor perturbations and show that any fast-roll model satisfies them, as in the case of inflation. We are interested in the "Sourced Bounce"scenario, where perturbations are sourced by a U(1) gauge field coupled to a bouncer scalar field. The requirement of a slightly red tilted scalar spectrum greatly restricts the allowed couplings between the scalar and the gauge field. We show that a viable slightly red scalar spectrum is achievable. However, within the fast-roll approximation the tensor-to-scalar ratio is in general r ≃ 1/9, inconsistent with current observations. We demonstrate the general result with an explicit example we dub "Intermediate contraction". We prove that small modifications in fast-roll that do not alter the Green's functions, do not result in r < 0.06 consistent with the data for more than an e-fold. Hence, a successful "Sourced Bounce"requires a different source or a significant deviation from fast-roll.
UR - http://www.scopus.com/inward/record.url?scp=85108422710&partnerID=8YFLogxK
U2 - 10.1088/1475-7516/2021/06/010
DO - 10.1088/1475-7516/2021/06/010
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AN - SCOPUS:85108422710
SN - 1475-7516
VL - 2021
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 6
M1 - 010
ER -