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Title: Light U(1)s in heterotic string models
Author: Mehta, Viraf M.
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2013
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We present the construction of heterotic string models built using the free fermionic formulation, and focus on how additional U(1)s may arise. We motivate an anomaly free combination, U(1)_\zeta, as a proton lifetime preserving symmetry external to a left--right symmetric gauge group. This same combination is found to nullify lepton number in U(1)_{B-L} to form a leptophobic combination, also in left--right symmetric models, which we compare to other leptophobic U(1) combinations constructed in the context of different gauge groups. We then accommodate U(1)_\zeta as a proton lifeguard symmetry in an effective field theory. We present a comparative study of how gauge coupling unification constraints may be satisfied when SO(10)xU(1)_\zeta\not\subset E_6 and when the U(1)_\zeta charges do have an E_6 embedding. We show that without such an embedding, current values of \sin^2\theta_W(M_Z) and \alpha_3(M_Z) rule these models out. We go on to discuss how viable string models with this property included may be constructed.
Supervisor: Faraggi, Alon E.; Rakow, Paul E. L. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QA Mathematics