17,148 research outputs found
Soft Supersymmetry-breaking terms and the \mu problem
The connection between Supergravity and the low-energy world is analyzed. In
particular, the soft Supersymmetry-breaking terms arising in Supergravity, the
problem and various solutions proposed to solve it are reviewed. The soft
terms arising in Supergravity theories coming from Superstring theory are also
computed and the solutions proposed to solve the problem, which are
naturally present in Superstrings, are also discussed. The soft terms
associated are given for the different solutions. Finally, the low-energy
Supersymmetric-spectra, which are very characteristic, are obtained.Comment: Based on talks given at different Conferences, 33 pages, late
Optical Unification
We discuss string scale unification facilitated by exotic matter with masses
at intermediate scales, between the observable sector supersymmetry breaking
scale and the string scale. We point out a mechanism by which string scale
unification may occur while producing a (lower) virtual unification scale
independent of the location of the intermediate scale and the value of the
string coupling. The apparent unification obtained by extrapolating low energy
gauge couplings is not accidental when this mechanism is invoked; virtual
unification is robust.Comment: 9 pages, references adde
Soft supersymmetry-breaking terms from supergravity and superstring models
We review the origin of soft supersymmetry-breaking terms in N=1 supergravity
models of particle physics. We first consider general formulae for those terms
in general models with a hidden sector breaking supersymmetry at an
intermediate energy scale. The results for some simple models are given. We
then consider the results obtained in some simple superstring models in which
particular assumptions about the origin of supersymmetry breaking are made.
These are models in which the seed of supersymmetry breaking is assumed to be
originated in the dilaton/moduli sector of the theory.Comment: 24 pages, to appear in the book `Perspectives on Supersymmetry',
World Scientific, Editor G. Kane; some comments and references adde
Complete structure of Z_n Yukawa couplings
We give the complete twisted Yukawa couplings for all the Z_n orbifold
constructions in the most general case, i.e. when orbifold deformations are
considered. This includes a certain number of tasks. Namely, determination of
the allowed couplings, calculation of the explicit dependence of the Yukawa
couplings values on the moduli expectation values (i.e. the parameters
determining the size and shape of the compactified space), etc. The final
expressions are completely explicit, which allows a counting of the DIFFERENT
Yukawa couplings for each orbifold (with and without deformations). This
knowledge is crucial to determine the phenomenological viability of the
different schemes, since it is directly related to the fermion mass hierarchy.
Other facts concerning the phenomenological profile of Z_n orbifolds are also
discussed, e.g. the existence of non--diagonal entries in the fermion mass
matrices, which is related to a non--trivial structure of the
Kobayashi--Maskawa matrix. Finally some theoretical results are given, e.g. the
no--participation of (1,2) moduli in twisted Yukawa couplings. Likewise, (1,1)
moduli associated with fixed tori which are involved in the Yukawa coupling, do
not affect the value of the coupling.Comment: 60 page
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