23,435 research outputs found
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
A discrete isodiametric result: the Erd\H{o}s-Ko-Rado theorem for multisets
There are many generalizations of the Erd\H{o}s-Ko-Rado theorem. We give new
results (and problems) concerning families of -intersecting -element
multisets of an -set and point out connections to coding theory and
classical geometry. We establish the conjecture that for such
a family can have at most members
Coloring curves that cross a fixed curve
We prove that for every integer , the class of intersection graphs
of curves in the plane each of which crosses a fixed curve in at least one and
at most points is -bounded. This is essentially the strongest
-boundedness result one can get for this kind of graph classes. As a
corollary, we prove that for any fixed integers and , every
-quasi-planar topological graph on vertices with any two edges crossing
at most times has edges.Comment: Small corrections, improved presentatio
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