More Supersymmetric Standard-like Models from Intersecting D6-branes on Type IIA Orientifolds

We present new classes of supersymmetric Standard-like models from type IIA \IT^6/(\IZ_2\times \IZ_2) orientifold with intersecting D6-branes. D6-branes can wrap general supersymmetric three-cycles of \IT^6=\IT^2\times \IT^2\times \IT^2, and any \IT^2 is allowed to be tilted. The models still suffer from additional exotics, however we obtained solutions with fewer Higgs doublets, as well as models with all three families of left-handed quarks and leptons arising from the same intersecting sector, and examples of a genuine left-right symmetric model with three copies of left-handed and right-handed families of quarks and leptons.Comment: 16 pages, REVTEX

The Global Gauge Group Structure of F-theory Compactification with U(1)s

We show that F-theory compactifications with abelian gauge factors generally exhibit a non-trivial global gauge group structure. The geometric origin of this structure lies with the Shioda map of the Mordell--Weil generators. This results in constraints on the U(1) charges of non-abelian matter consistent with observations made throughout the literature. In particular, we find that F-theory models featuring the Standard Model algebra actually realise the precise gauge group [SU(3)xSU(2)xU(1)]/Z6. Furthermore, we explore the relationship between the gauge group structure and geometric (un-)higgsing. In an explicit class of models, we show that, depending on the global group structure, an SU(2)xU(1) gauge theory can either unhiggs into an SU(2)xSU(2) or an SU(3)xSU(2) theory. We also study implications of the charge constraints as a criterion for the F-theory 'swampland'.Comment: 37 pages; v2: improved derivation of global group structure in section 2, extended discussion on the 'swampland' conjecture in section 5, references added, v2 accepted for publication in JHEP; v3: typos correcte

Infra-red fixed points at the boundary

Gauged supergravities (in four and five dimensions) with eight supercharges and with vector supermultiplets have a unique ultra-violet (UV) fixed point on a given physical domain \cal M of the space of the scalar fields. We show that in these models the infra-red (IR) fixed points are located on the boundary of \cal M, where the space-time metric becomes singular.Comment: 10 pages, Latex, 2 figure