Eur. Phys. J. C (2007) 49: 803-813
https://doi.org/10.1140/epjc/s10052-006-0160-z

Regular Article - Theoretical Physics

Higgs–matter splitting in quasi-realistic orbifold string GUTs

¹ Mathematical Sciences Department, University of Liverpool, Liverpool, L69 7ZL, UK
² Theoretical Physics Department, University of Oxford, Oxford, OX1 3NP, UK
³ Theory Division, CERN, 1211, Geneva 23, Switzerland

^* e-mail: faraggi@sune.amtp.liv.ac.uk

Received: 16 October 2006
Published online: 9 December 2006

Abstract

E₆ grand unification combines the standard model matter and Higgs states in the single 27 representation. I discuss how the E₆ structure underlies the quasi-realistic free fermion heterotic-string models. E₆→SO(10)×U(1) breaking is obtained by a GSO phase in the N=1 partition function. The equivalence of this symmetry breaking phase with a particular choice of boundary condition basis vectors, which is used in the quasi-realistic models, is demonstrated in several cases. As a result, matter states in the spinorial 16 representation of SO(10) arise from the twisted sectors, whereas the Higgs states arise from the untwisted sector. Possible additional phenomenological implications of this E₆ symmetry breaking pattern are discussed.