Abstracts of Talks
I will list and comment on the main issues of string phenomenology with low or high string scale. I will then describe a simple compactification framework for moduli stabilization, model building, calculable supersymmetry breaking and computable radiative corrections.
I will describe recent developments in grand unified model building in four dimensions A simple and predictive class of SO(10) models with natural doublet-triplet splitting and consistent gauge coupling unification will be presented. These models also provide satisfactory solutions to various puzzles of the supersymmetric standard model, including the fermion mass puzzle, the mu problem, and the issue of flavor changing neutral currents. Experimental signatures in proton decay, supersymmetric particle spectrum, neutrino oscillations, and rare processes will be discussed.
I will describe 'what if' scenarios based on having a low energy string scale close to those attainable at the LHC. I will show that in general one could hope that Z' particles and some colored exotics could be visible at the LHC and these are not ruled out by current experiments. I will describe some of the signatures for new particles and how one might go about improving the chances of finding them if they are there.
We review the progress on stringy D-instantons and their implications for modifying charged matter couplings. We focus on supersymmetry breaking effects within globally consistent semi-realistic Type I constructions.
The "landscape" provides a framework in which to ask about the possible role of symmetries in a fundamental theory of interactions. This talk will focus principally on (low energy) supersymmetry and on discrete symmetries. In the case of supersymmetry, we will argue that, while supersymmetric stationary points of classical equations may be exceptional, considerations of stability might favor supersymmetric and approximately supersymmetric states. Similarly, states exhibiting discrete symmetries are rare, but, at least in the case of symmetries, some of these states may plausibly be cosmological attractors.
It is well known that D-brane instantons can generate contributions to the effective superpotential of gauge theories living on D-branes which are perturbatively forbidden by global U(1) symmetries. We extend this idea to theories with supersymmetry breaking, studying the effect of D-brane instantons stretched between the SUSY-breaking and visible sectors. Analogously to what happens in the SUSY case, this mechanism can give rise to perturbatively forbidden soft terms (among other effects). We introduce and discuss general properties of instanton mediation. We illustrate our ideas in simple Type IIB toroidal orientifolds.
We describe some recent progress on realizing Grand Unified Theories (GUTs) from local models derived from F-theory. After providing some motivation for F-theory as a natural arena for local model building as well as GUT model building, we present the primary ingredients of such models. Next, we show how these ingredients address some issues typically present in purely four-dimensional GUTs. Finally, we explain how to incorporate the effects of supersymmetry breaking in this framework.
We classify possible types of pseudomoduli which arise when supersymmetry is dynamically broken in infrared-free low-energy theories. We show that, even if the pseudomoduli potential is generated only at higher loops, there is a regime where the potential can be simply determined from a combination of one-loop running data. In this regime, we compute whether the potential for the various types of pseudomoduli is safe, has a dangerous runaway to the UV cutoff of the low-energy theory, or is incalculable. Our results are applicable to building new models of supersymmetry breaking. We apply the results to survey large classes of models.
I describe, in general terms, string theory constructions where dynamical SUSY-breaking occurs in a strongly coupled gauge theory from which (some of the) MSSM matter fields emerge as composites. The SUSY breaking soft terms arise from a combination of gaugino mediation and ``compositeness" contributions for the composite fields. AdS/CFT duality plays a crucial role in the construction and 4D interpretation of this class of models.
We discuss how the bottom up aproach for string model building fits with recent developments on moduli stabilisation, especially with the LARGE volume scenario.
I discuss some of the phenomenological properties of a particular orbifold compactification of the E(8)xE(8) heterotic string. In particular, I will discuss the spectrum of states, the local GUT and orbifold GUT limits, gauge coupling unification, Yukawa couplings, family symmetry and much more.
Nathan Seiberg and David Shih
Some recent advances in gauge mediation of supersymmetry breaking will be discussed.
Analysis of some simple corners of the type II landscape suggests that low-energy particle theory may be somewhat freely chosen in the string landscape, while cosmology may be more constrained. Anecdotal evidence for this conclusion is given from intersecting brane models and flux vacua. An interesting example arises in magnetized brane models on K3, where results of Nikulin lead to a precise statement of the generality of features of the low-energy field theory.