Families as neighbors in extra dimension

G. Dvali, M. Shifman

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124 Scopus citations


We propose a new mechanism for explanation of the fermion hierarchy without introducing any family symmetries. Instead, we postulate that different generations live on different branes embedded in a relatively large extra dimension, where gauge fields can propagate. The electroweak symmetry is broken on a separate brane, which is a source of exponentially decaying Higgs profile in the bulk. The resulting fermion masses and mixings are determined by an exponentially suppressed overlap of the fermion and Higgs wave functions and are automatically hierarchical even if all copies are identical and there is no hierarchy of distances. In this framework the well known pattern of the "nearest neighbor mixing" is predicted due to the fact that the families are literally neighbors in the extra space. This picture may also provide a new way of a hierarchically weak supersymmetry breaking, provided that the combination of three family branes is a non-BPS configuration, although each of them, individually taken, is. This results in exponentially weak supersymmetry breaking. We also discuss the issue of embedding identical branes in the compact spaces and localization of the fermionic zero modes.

Original languageEnglish (US)
Pages (from-to)295-302
Number of pages8
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number3-4
StatePublished - Mar 2 2000

Bibliographical note

Funding Information:
We would like to thank Savas Dimopoulos, Gregory Gabadadze, Alex Pomarol and Massimo Porrati for useful discussions. A part of this work was done at ITP, Santa Barbara, where we were participants of the program “Supersymmetric Gauge Dynamics and String Theory.” We are grateful to the ITP staff for hospitality. This work was supported in part by DOE under Grant No. DE-FG02-94ER40823, by National Science Foundation under Grant No. PHY94-07194, and by David and Lucile Packard Foundation Fellowship for Science and Engineering.


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