4,224 research outputs found
Standard Model Engineering with Intersecting Branes
I briefly describe the recent construction of the first specific string
D-brane models yielding just the SM massless fermion spectrum. One of the most
remarkable facts predicted by these constructions is that the global symmetries
of the SM like Baryon and Lepton numbers as well as the axial are
gauged symmetries whose anomalies are cancelled by a Green-Schwarz mechanism
only in the case of three quark-lepton generations. Proton stability and the
Dirac nature of neutrino masses are thus a prediction of these theories. This
is work done in collaboration with Fernando Marchesano and Raul Rabadan.Comment: 10 pages, Latex file, no figures. Contribution to the proceedings of
SUSY-01, Dubna (Russia), June 200
Topics in String Unification
I discuss several aspects of strings as unified theories. After recalling the
difficulties of the simplest supersymmetric grand unification schemes I
emphasize the distinct features of string unification. An important role in
constraining the effective low energy physics from strings is played by
symmetries. The discussed topics include the unification of coupling
constants (computation of and at the weak
scale), supersymmetry breaking through gaugino condensation, and properties of
the induced SUSY-breaking soft terms. I remark that departures from
universality in the soft terms are (in contrast to the minimal SUSY model)
generically expected.Comment: 22 pages. Talk given at the ``Workshop on Electroweak Physics Beyond
the Standard Model'', Valencia, 3-5 October 199
The Fluxed MSSM
Recent developemnts in string compactifications in the presence of
antisymmetric field backgrounds suggest a new simple and predictive structure
for soft terms in the MSSM depending only on two parameters. They give rise to
a positive definite scalar potential, a solution to the -problem, flavor
universality and absence of a SUSY-CP problem.Comment: 23 pages, no figures. Addendum on intersecting D7-branes included.
Referencese added and minor change
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