Dear All members,
We are pleased to announce a Journal club by Sang Hui Im.
* Title: Relaxing the Electroweak Scale : the Role of Broken dS Symmetry
* Speaker: Sang Hui Im(IBS-CTPU)
* Date: 12:00-1:00 PM, 28 Aug 2015
* Abstract: Recently, a novel mechanism to address the hierarchy problem has been proposed, where the hierarchy between weak scale physics and any putative cutoff M is translated into a parametrically large field excursion for the so-called relaxion field, driving the Higgs mass to values much less than M through cosmological dynamics. In its simplest incarnation, the relaxion mechanism requires nothing beyond the standard model other than an axion (the relaxion field) and an inflaton. In this note, we critically re-examine the requirements for successfully realizing the relaxion mechanism and point out that parametrically larger field excursions can be obtained for a given number of e-folds by simply requiring that the background break exact de Sitter invariance. We discuss several corollaries of this observation, including the interplay between the upper bound on the scale M and the order parameter epsilon associated with the breaking of dS symmetry, and the possibility that the relaxion could play the role of a curvaton. We find that a successful realization of the mechanism is possible with as few as O(10^3) e-foldings, albeit with a reduced cutoff M ~ 10^6 GeV for a dark QCD axion and outline a minimal scenario that can be made consistent with CMB observations.
* References: arXiv 1507.08649
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[ http://doodle.com/g7mc2fv2nkq9fevz ]
We look forward to your participation in the Journal club.
Thank you.
Sincerely,
Sung Yeop Na