Left-right symmetric heterotic-string derived models - art. no. 066001

Recently it was demonstrated that free fermionic heterotic strings can prod uce models with solely the minimal supersymmetric standard model states in the low energy spectrum. This unprecedented result provides further strong evidence for the possibility that the true string vacuum shares some of the properties of the free fermionic models. Past free fermionic models have f ocused on several possible unbroken observable SO(10) subgroups at the stri ng scale, which include the flipped SU(5) (FSU5), the Pati-Salam (PS) strin g models, and the string standard-like models (SLM). We extend this study t o include the case in which the SO(10) symmetry is broken to the left-right symmetric (LRS) gauge group, SO(10)-->SU(3)(c) x U(1)(B-L)SU(2)(L) x SU(2) (R). We present several models of this type and discuss their phenomenologi cal features. The most striking new outcome of the LRS string models, in co ntrast with the case of the FSU5, the PS, and the SLM string models, is tha t they can produce effective field theories that are free of Abelian anomal ies. We discuss the distinction between the two types of free fermionic mod els which result in the presence, or absence, of an anomalous Li(1). As a c ounterexample we also present a LRS model that does contain an anomalous U( 1). Additionally, we discuss how in string models the standard model spectr um may arise from the three 16 representations of SO(10), while the weak hy percharge does not have the canonical SO(10) embedding.