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It is argued that recent developments point to the existence of an AdS_3 x S^2 x T^5 holographic dual for the 2D CFT living on the worldsheet of N coincident heterotic strings in a T^5 compactification, which can in turn be described by an exact worldsheet CFT. A supergravity analysis is shown to imply that the global supergroup is Osp(4^*|4), with 16 supercharges and an affine extension given, surprisingly, by a nonlinear N=8 2D superconformal algebra. Possible supergroups with 16 supercharges are also found to match the expected symmetries for T^n compactification with 0<=n<=7.
We analyze Yukawa unification in the the context of $E_8times E_8$ heterotic Calabi-Yau models which rely on breaking to a GUT theory via a non-flat gauge bundle and subsequent Wilson line breaking to the standard model. Our focus is on underlying GU
The three generation heterotic-string models in the free fermionic formulation are among the most realistic string vacua constructed to date, which motivated their detailed investigation. The classification of free fermion heterotic string vacua has
We develop techniques, based on differential geometry, to compute holomorphic Yukawa couplings for heterotic line bundle models on Calabi-Yau manifolds defined as complete intersections in projective spaces. It is shown explicitly how these technique
The $Z_2times Z_2$ heterotic string orbifold gives rise to a large space of phenomenological three generation models that serves as a testing ground to explore how the Standard Model of particle physics may be incorporated in a theory of quantum grav
We extend the classification of fermionic $mathbb{Z}_2timesmathbb{Z}_2$ heterotic string orbifolds to non--supersymmetric Pati--Salam (PS) models in two classes of vacua, that we dub $tilde S$--models and $S$--models. The first correspond to compacti