39 research outputs found
Standard Model Compactifications of IIA Z3 x Z3 Orientifolds from Intersecting D6-branes
We discuss the construction of chiral four dimensional orientifold compactifications of IIA theory, using D6-branes
intersecting at angles and not aligned with the orientifold O6 planes.
Cancellation of mixed U(1) anomalies requires the presence of a generalized
Green-Schwarz mechanism mediated by RR partners of closed string untwisted
moduli. In this respect we describe the appearance of three quark and lepton
family non-supersymmetric orientifold
models with only the massless spectrum of the SM at low energy that can have
either no exotics present and three families of 's (A-model
class) or the massless fermion spectrum of the N=1 SM with a small number of
massive non-chiral colour exotics and in one case with extra families of
's (B-model class). Moreover we discuss the construction of
SU(5), flipped SU(5) and Pati-Salam
GUTS - the latter also derived from adjoint breaking - with only the SM at low
energy. Some phenomenological features of these models are also briefly
discussed. All models are constructed with the Weinberg angle to be 3/8 at the
string scale.Comment: 31 pages, 1 figure; v2: typos corrected, comments in the introduction
added v3:35 pages, Pati-Salam G422 models & comments on split susy scenario
and refs added; to appear in NP
4D GUT (and SM) Model Building from Intersecting D-Branes
We provide a general overview of the current state of the art in three
generation model building proposals - using intersecting D-brane toroidal
compactifications of IIA string theories - which have, only, the SM at low
energy. In this context, we focus on these model building directions, where
natural non-supersymmetric constructions based on
, SU(5) and flipped SU(5) GUT groups,
have at low energy only the Standard Model. In the flipped SU(5) GUTS, the
special build up structure of the models accommodates naturally a see-saw
mechanism and a new solution to the doublet-triplet splitting problem.Comment: 8 pages, LaTex, Contribution to the Proceedings of the "String
Phenomenology 2003" conference, Durham, England, 29th July - 4th August 200