Nonanomalous discrete R symmetry decrees three generations

Jason L. Evans, Masahiro Ibe, John Kehayias, Tsutomu T. Yanagida

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


We show that more than two generations of quarks and leptons are required to have an anomaly free discrete R symmetry larger than R parity, provided that the supersymmetric standard model can be minimally embedded into a grand unified theory. This connects an explanation for the number of generations with seemingly unrelated problems such as supersymmetry breaking, proton decay, the μ problem, and the cosmological constant through a discrete R symmetry. We also show that three generations is uniquely required by a nonanomalous discrete R symmetry in classes of grand unified theories such as the ones based on (semi)simple gauge groups.

Original languageEnglish (US)
Article number181801
JournalPhysical review letters
Issue number18
StatePublished - Nov 2 2012


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