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 $duality$ symmetries. The discussed topics include the unification of coupling constants (computation of $\sin ^2\theta _W$ and $\alpha _s$ 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 $\mu$-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

SU(N)→Z(N){\rm SU}(N) \to {\rm Z}(N) dual superconductor models: the magnetic loop ensemble point of view

In this work, we initially discuss some physical properties of effective ${\rm SU}(N) \to {\rm Z}(N)$ YMH models, emphasizing the important role of valence gluons. Next, we review how adjoint fields are naturally generated as an effective description of "adjoint" loops in $4D$. Finally, we discuss the consequences that can be learnt from this point of view, and briefly comment on some improvements.Comment: 14 pages, 7 figures, proceedings of the XII Quark Confinement conference, Thessaloniki, Greece, from 28th August to 4rd September 201