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Nonlocal Cosmology II --- Cosmic acceleration without fine tuning or dark energy

Deser, S. and Woodard, R. P. (2019) Nonlocal Cosmology II --- Cosmic acceleration without fine tuning or dark energy. Journal of Cosmology and Astroparticle Physics, 2019 (6). Art. No. 34. ISSN 1475-7516. doi:10.1088/1475-7516/2019/06/034.

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We present an improved version of our original cosmological model to explain the current phase of cosmological acceleration without resorting to a cosmological constant or any other mass scale. Like the original, this phenomenological approach is based on an effective quantum gravitational action, but now depends on the original nonlocal dimensionless scalar X = ^(−1) R only through Y = ^(−1) g^(μν) X,_μ X,_ν. Both X and Y are quiescent during the radiation-dominated (R=0) era, both only grow logarithmically during matter dominance, and neither affects the propagation of gravitational radiation. However, while X has the same sign for gravitationally bound systems as for cosmology, we show that the sign of Y differs for the two cases: it is positive for cosmology and negative for strongly gravitationally bound systems. We can therefore enforce the ΛCDM expansion history by making a suitable choice of the nonlocal distortion function f(Y) for Y > 0, while ensuring that there is no change in the heavily constrained solar system phenomenology simply by making f vanish for Y < 0 without discontinuity. The required f(Y>0) is determined numerically to have a strikingly simple exponential form.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Deser, S.0000-0001-9285-9434
Additional Information:© 2019 IOP Publishing Ltd and Sissa Medialab. Received 22 February 2019; Accepted 3 June 2019; Published 17 June 2019. We are grateful to M. Maggiore for calling our attention to the problem with the original model. SD’s work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award Number de-sc0011632. RPW was partially supported by NSF grants PHY1506513 and PHY-1806218, and by the Institute for Fundamental Theory at the University of Florida.
Group:Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0011632
University of FloridaUNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Issue or Number:6
Classification Code:PACS numbers: 04.50.Kd, 95.35.+d, 98.62.-g
Record Number:CaltechAUTHORS:20190228-120120767
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Official Citation:S. Deser and R.P. Woodard JCAP06(2019)034
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93353
Deposited By: Joy Painter
Deposited On:28 Feb 2019 20:19
Last Modified:12 Jul 2022 17:35

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