# Brans-Dicke supergravity and the Lambda naturalness problem

Conference paper

Hewitt, M. 2015.

*Brans-Dicke supergravity and the Lambda naturalness problem.*

Authors | Hewitt, M. |
---|---|

Type | Conference 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 $\Lambda$. |

Keywords | Dark energy; cosmological constant |

Year | 2015 |

Conference | COSMO 15 - 19th International Conference on Particle Physics and Cosmology |

Official URL | https://indico.cern.ch/event/438475/contributions/1090897/ |

Related URL | https://indico.cern.ch/event/438475/ |

File | |

Funder | Canterbury Christ Church University |

Publication process dates | |

Deposited | 17 Sep 2015 |

Completed | 10 Sep 2015 |

Output status | Unpublished |

https://repository.canterbury.ac.uk/item/87717/brans-dicke-supergravity-and-the-lambda-naturalness-problem

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