Brans-Dicke supergravity and the Lambda naturalness problem

Conference paper


Hewitt, M. 2015. Brans-Dicke supergravity and the Lambda naturalness problem.
AuthorsHewitt, M.
TypeConference paper
Description

The successful $\Lambda CDM$ cosmological model requires a small but nonzero $\Lambda$ which appears to have an unnaturally small value compared to the supersymmetry breaking scale, typically $O(10^{-60}) m_{3/2}^4$ for $m_{3/2} \sim 10 TeV$. We explore the possibility of solving this naturalness problem in a special class of no-scale supergravity models which arise from a supersymmetric version of Brans-Dicke gravity, in which the Volkov and Brans-Dicke multiplets may be identified. These may be embedded in compactified string models, with the Brans-Dicke scalar given by the combination of dilaton and compactification breathing modes which leaves the 4 dimensional gauge couplings fixed. Assuming that 4 dimensional physics has an approximate symmetry under changes in this mode broken only by couplings between the low energy and gravitational or string sectors, the main one loop contribution to $\Lambda$ cancels between Brans-Dicke and gravitational (conformal compensator) F terms, and the leading contributions to $\Lambda$ now appear to be $O(m_{3/2}^8 m_{p}^{-4)}$, enabling a natural reconciliation between observational and particle physics estimates for $\Lambda$.
The Brans-Dicke scalar has a range $O(m_{3/2}^{-1})$, lifting observational constraints on scalar gravity in this scenario.

KeywordsDark energy; cosmological constant
Year2015
ConferenceCOSMO 15 - 19th International Conference on Particle Physics and Cosmology
Official URLhttps://indico.cern.ch/event/438475/contributions/1090897/
Related URLhttps://indico.cern.ch/event/438475/
File
FunderCanterbury Christ Church University
Publication process dates
Deposited17 Sep 2015
Completed10 Sep 2015
Output statusUnpublished
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https://repository.canterbury.ac.uk/item/87717/brans-dicke-supergravity-and-the-lambda-naturalness-problem

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