List of Talks


Title & Abstract

Senarath (Shanta) de Alwis

A Minimal Model of Supersymmetry Breaking

A consistent theory of supersymmetry breaking must have a hidden sector an observable sector and must be embedded in a locally supersymmetric theory which arises from string theory. For phenomenological reasons it must also transmit supersymmetry from the hidden to the visible sector in a dominantly flavor neutral manner. Also any such theory of supersymmetry breaking has to take into acount the problem of quadratic divergences which arise once the theory is embedded in supergravity. A model which incorporates all these features with just the bare minimum of necessary supergravity/string theory moduli fields coupled to the minimally supersymmetric standard model, is presented. Every other model has either an extra sector or more fine-tuning or both.

Bjorn Andreas

Stable bundles for heterotic string models

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The search for heterotic GUT and standard model vacua has led to various new constructions of stable vector bundles on elliptically respectively K3 fibered Calabi-Yau threefolds which will be reviewed and discussed.

Ignatios Antoniadis

Physics with magnetized branes

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Nima Arkani-Hamed


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Katrin Becker

Torsional Heterotic Geometries

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We construct some new examples of torsional heterotic backgrounds using duality with orientifold flux compactifications. We then explain how duality provides a solution to the heterotic string Bianchi identity which is an equation of Monge-Ampere type. Finally, we propose the existence of a much larger class of compact torsional geometries based on intuition from string duality.

Melanie Becker

New Heterotic Flux Compactifications

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Massimo Bianchi

Twists and Shifts

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For vacuum configurations with open and unoriented strings, the role of (a-) symmetric twists and (non-)geometric shifts has not been systematically taken into account so far. We remedy the situation in the perspective of moduli stabilization and susy breaking in combination with other (non-)perturbative effects.

Ralph Blumenhagen

Multi D-brane Instanton Effects, String GUT and CC

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Lev Borisov

On Calabi-Yau varieties with non-abelian fundamental groups of order 64

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I will describe the construction (joint with Zheng Hua) of Calabi-Yaus with large fundamental groups that are obtained as resolutions of complete intersections of four quadrics in P^7. The key ingredient is the use of the holomorphic Lefschetz formula to classify the possible group actions.

Vincent Bouchard

The High Country region of the string landscape

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Pablo Camara

Torsion Induced SUSY-Breaking Soft-terms

I discuss the conditions for having no-scale solutions of type IIA and IIB supergravity compactified on manifolds of SU(3) structure, where the supersymmetry is spontaneously broken by the intrinsic torsion. The concrete expressions for geometrically induced mu-terms for D5, D6 and D9-branes on twisted tori are presented. Some patterns of soft supersymmetry breaking terms which arise for pure moduli mediation are discussed.

Michele Cicoli

General Analysis of LARGE Volume Scenarios with String Loop Moduli Stabilisation

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We study the necessary and sufficient topological conditions for general Calabi-Yaus to get a non-supersymmetric AdS exponentially large volume minimum of the scalar potential in flux compactifications of IIB string theory. It turns out that string loop corrections play a crucial role to realise exponentially large volume minima for fibration Calabi-Yaus and to stabilise 4-cycles which support chiral matter. The robustness of these results is due to the "extended no-scale structure": for arbitrary Calabi-Yaus, the leading contribution of these corrections to the scalar potential is always vanishing. We use the Coleman-Weinberg potential to motivate this cancellation from the viewpoint of low-energy field theory. We briefly discuss the potential cosmological implications.

Joe Conlon

Continuous Global Symmetries in String Theory

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Emanuel Diaconescu


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Michael Dine

Symmetries in String Theory

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Emilian Dudas

Multi-instantons and string loop corrections

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P. Frampton

Maldacena-inspired phenomenology

Thomas Grimm

U(1) Mediation of Fluxed Supersymmetry Breaking

I discuss the mediation of supersymmetry breaking triggered by background fluxes in Type IIB orientifold compactifications with N=1 supersymmetry. For compactifications on non-Kaehler backgrounds the mediation can arise due to an U(1) vector multiplet coupling to both a hidden supersymmetry breaking flux sector and a visible brane sector. I will discuss the construction of the required orientifolds with candidate local geometries for the hidden and visible sector. The computation of the relevant BPS invariants confirms the topological connection between the two sectors.

Mark Gross

Some Calabi-Yau manifolds with small Betti numbers.

I will discuss a number of example of Calabi-Yau threefolds with small Betti numbers and large fundamental group which may be useful for string compactifications.
Many of these examples were discovered with Sorin Popescu, and are fibred in abelian surfaces. One of the examples has h^{1,1}=h^{1,2}=2 and fundamental group
Z_8 x Z_8

Monika Gabriele Honecker

Towards the supersymmetric standard model on intersecting branes - the Z6' case

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Intersecting D6-branes on orbifold backgrounds provide calculable tools for four dimensional low-energy spectra and couplings. The abundance of phenomenologically appealing spectra, in particular those close to the MSSM, is strongly background dependent. In this talk, I will mainly focus on a fertile region, the Z6' orbifold. (and compare it with other orbifolds if time permits)

Elias Kiritsis

Getting the Standard Model from free-field Orientifolds

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Igor Klebanov

Warped Conifolds and Their Applications to Cosmology

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Maximilian Kreuzer

Constructing Calabi-Yau 3-folds and their mirrors via conifold transitions

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A surprisingly large class of new Calabi-Yau 3-folds with small Picard numbers and their mirrors can be constructed by conifold transitions from toric hypersurfaces, generalizing the mirror construction of Calabi-Yau complete intersections in Grassmannians and flag manifolds. I'll describe our recent results with Batyrev and also summarize work on torsion in cohomology for hypersurfaces and complete intersections as well as phenomenological applications.

Bumseok Kyae

Orbifold SUSY GUT from the Heterotic String

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From the string partition function, we derive the mass-shell and GSO projection conditions valid for Kaluza-Klein (KK) as well as massless states in the heterotic string theory compactified on a non-prime orbifold. Using the obtained conditions we construct a 4D string standard model, which is embedded in a 6D SUSY GUT by including KK states above the compactification scale. We discuss the stringy threshold corrections to gauge couplings, which include the Wilson line effects. We point out the differences in string and field theoretic orbifoldings.

Zygmunt Lalak

Gravity in Gauge Mediation

Usually gauge mediation of supersymmetry breaking is discussed independently of the structure of the microscopic sector which is responsible for supersymmetry breakdown. We shall discuss in specific models how the internal structure of that sector determines the structure and scales of the supersymmetry breaking terms. We demonstrate the role of supergravity induced corrections to the scalar potential, in particular the constraints imposed by the cancellation of the cosmological constant. We include moduli into the discussion

Louis Leblond

Inflation from Wrapped Branes

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In brane inflation models, the field range in Planck units for the inflaton is geometrically limited and this imposes strong constraints in model building. In this talk I will discuss how one can extend the field range by using higher dimensional wrapped branes. I will discuss in details a possible scenario where a D5-brane falls down a throat and self-annihilate. DBI inflation could be realized in this set-up with a strong non-Gaussian signal.

Tao Liu

Dynamically Solving mu/Bmu Problem in Gauge-mediated SUSY Breaking

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Dieter Luest

Supersymmetric, non-supersymmetric and inflationary type II string vacua

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We discuss type II orientifold compactifications on generalized geometries with and without supersymmetry. In addition we also discuss a particular inflationary string model which leads to specific astrophysical observables.

Juan Maldacena

Conformal Collider Physics

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We discuss energy correlations as infrared finite observables in conformal field theories. We discuss an application of the light-cone operator product expansion for determining the small angle singularities of the energy correlations. We analyze this at both weak and strong coupling. We also discuss general properties of energy correlation functions.

Fernando Marchesano

Non-perturbative F-terms across stability lines

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Jock McOrist

Type IIB Flux Vacua from the String Worldsheet

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In this talk I will present recent progress towards understanding d=4 Minkowski flux vacua using string worldsheet techniques. In a simple class of examples I will show how to derive spacetime warping and the Gukov-Vafa-Witten superpotential for complex structure moduli.

Ilarion Melnikov

Linear Sigma Models and (0,2) Mirror Symmetry

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I will discuss some recent progress on computing Yukawa couplings in (0,2) Heterotic theories obtained as IR limits of deformed (2,2) gauged linear sigma models.  I will show that the combination of the linear structure and the existence of a related half-twisted sigma model render these couplings computable in terms of the parameters of the linear model.  Finally, I will comment on the Implications of these computations for (0,2) mirror symmetry.

David Morrison

Limitations of Geometric Engineering: Implications for Model Building

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Slava Mukhanov

Inflation and CMB fluctuations

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Yu Nakayama

Moduli stabilization in stringy ISS model

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We present a stringy realization of the ISS metastable SUSY breaking model with moduli stabilization. The mass moduli of the ISS model is stabilized by gauging of a U(1) symmetry and its D-term potential. The SUSY is broken both by F-terms and D-terms. It is possible to obtain de-Sitter vacua with a vanishingly small cosmological constant by an appropriate fine-tuning of flux parameters.

Pran Nath

A New Path to SO(10) Unification and Proton Decay

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Stefan Groot Nibbelink

Heterotic Model Building on Orbifold Resolutions

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Heterotic string on orbifolds give an easy insight of the possible phenomenological models that could come out of string theory. In particular recently it has been shown that it is possible to get a rather large class of models that have exactly the MSSM spectrum up to states that do not directly couple to the SM gauge group. Unfortunately orbifolds only define very special points in moduli space, to obtain a more complete picture of heterotic phenomenology one also has to investigate on smooth Calabi-Yaus. We construct such spaces as blow-ups of orbifolds with Abelian gauge bundle backgrounds, and make a start in investigating the properties of the resulting models.

Hans Peter Nilles

The Gaugino Code

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Gauginos may play a crucial role in the search for supersymmetry at the Large Hadron Collider (LHC). Mass predictions for gauginos are rather robust and often related to the values of the gauge couplings. We analyse the ratios of gaugino masses in the LHC range for various schemes of supersymmetry breakdown and mediation in the framework of string inspired models. Three distinct mass patterns emerge.

Erik Plauschinn

Moduli Stabilisation versus Chirality

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In this talk, the general question of implementing a chiral MSSM like D-brane sector in Type IIB orientifold models together with complete moduli stabilisation via F-terms induced by fluxes and space-time instantons is analysed. It turns out that in principle this is not possible and D-terms have to be taken into account. For a concrete model on P_[1,3,3,3,5][15] such a mechanism is illustrated.

Fernando Quevedo

LARGE volume string scenarios

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Michael Ratz

MSSMs from Heterotic Orbifolds

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Recent progress in embedding the standard model in string theory is described.
Models with the following features are discussed: (i) exact MSSM spectrum below the unification scale; (ii) R parity; (iii) hierarchical Yukawa couplings with non-trivial mixing; (iv) solution to the mu problem; (v) see-saw suppressed neutrino masses. Potential problems with dimension five proton decay are also commented on.

Masa-Hiko Saito

A Calabi-Yau threefold with abelian fibration and Z/2Z-action

We will report on a new example of Calabi-Yau threefold with a fibration of Jacobians of curves of genus $2$ with Z/2Z action which may be useful for string compactifications.

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Bert Schellekens

Non-supersymmetric Gepner orientifolds

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Michael Schulz

String Junctions, Abelian Fibrations and Flux/Geometry Duality

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In previous work, it was argued that the type IIB T^6/Z_2 orientifold with a choice of flux preserving N=2 supersymmetry is dual to a class of purely geometric type IIA compactifications on abelian surface (T^4) fibered Calabi-Yau threefolds.  In this talk, I will provide two concrete descriptions of the resulting Calabi-Yau duals.  The first is a monodromy based description, analogous to F-theory encoding of Calabi-Yau geometry via 7-branes and string junctions, except for T^4 rather than T^2 fibers.  The second is an explicit algebro-geometric construction in which the T^4 fibers arise as the Jacobian tori of a family genus-2 curves.  The talk will conclude with a discussion of applications of this work, including applications to D-brane instantons and D(imensional) duality.

Nathan Seiberg

Gauge mediation of SUSY breaking

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Savdeep Sethi

Non-Supersymmetric String Theory

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Qaisar Shafi

Higgs Mass Bounds in the light of Neutrino Oscillations

An understanding of the observed solar and atmospheric neutrino oscillations requires new physics beyond the Standard Model (SM). We discuss how this new physics also modifies the vacuum stability and perturbativity bounds on the SM Higgs mass.

Sarah Shandera

Testing stringy non-Gaussianity

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Non-Gaussianity may be a powerful means to distinguish between inflationary models. It is a particularly interesting probe since it may well be sensitive to UV physics and is observable in the near future. Some string theory models of inflation that predict observably large non-Gaussianity also predict that the magnitude of non-Gaussianity grows on small scales, and so may be tested with large scale structure measurements, including cluster number counts. This talk will explore a few theoretical and observational implications of scale-dependent non-Gaussianity.

Jing Shao

Solving the moduli and dark matter problem in the G_2 MSSM scenario

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We address the cosmological moduli/gravitino problems and the issue of too little thermal but excessive non-thermal dark matter from the decays of moduli in a phenomenological scenario motivated from G2 compacification with moduli stabilized.

Gary Shiu

Progress in Warped String Compactifications

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Warped compactifications have found interesting applications in cosmology and particle physics. Describing these backgrounds is also conceptually challenging. In this talk, I will describe some recent work on understanding warped string vacua as well as the effective theory describing them.

Eva Silverstein

Monodromy in the CMB: Gravity Waves and String Inflation

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Paul Steinhardt

Dark Energy Theorems and Other Curious Corollaries

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Balazs Szendroi

Quivers, Dimers and Non-commutative Donaldson-Thomas Invariants

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Certain limits of local Calabi-Yau threefolds are well known to be described by quiver theories, which in turn can be combinatorially defined by the associated dimer model. I will explain how this gives rise to non-commutative analogues of DT invariants, integer invariants closely related to BPS state counting, and how their generating functions can in some cases be computed in closed form, exhibiting wall-crossing behaviour.

Gonzalo Torroba

Kinetic terms in string compactifications

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We develop a general formalism to construct the kinetic terms of the low energy degrees of freedom in string compactifications. It is shown that the correct 4d fields arise from fluctuations satisfying a (warped) generalization of the harmonic gauge in Calabi-Yau manifolds. This simplifies considerably the dimensional reduction, enabling us to find explicitly the field space metric. The method is then applied to warped flux compactifications.

Li-Sheng Tseng

Orbifold and local heterotic flux geometry.

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presented with Shing-Tung Yau

Henry Tye

Mobility in the Cosmic Landscape

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Cumrun Vafa

F-theory and GUTs: Experimental Predictions

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Herman Verlinde


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Liantao Wang

Zprime Mediated supersymmetry Breaking.

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Taizan Watari

Heterotic--F Theory Duality Revisited

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[based on an article arXiv:0805.1057] F-theory is a better framework than the perturbative Type IIB string theory, when it comes to describe Yukawa couplings of quarks and leptons. How should quarks and leptons be described in F-theory? I would like to talk about recent progress on this issue that was not covered by Donagi-Wijnholt or Beaseley-Heckman-Vafa. Covering matter curves and chirality formulae will be the main theme of the talk.

Alexander Westphal

Monodromy in the CMB: Gravity Waves and String Inflation

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We present a simple mechanism for obtaining large-field inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to phi^(2/3) in terms of the canonically normalized field phi, yielding predictions for the tilt of the power spectrum and the tensor-to-scalar ratio, $n_s\approx 0.98$ and $r\approx 0.04$ with 60 e-foldings of inflation; we note also the possibility of a variant with a candidate inflaton potential proportional to phi^(2/5). The basic mechanism involved in extending the field range - monodromy in D-branes as they move in circles on the manifold - arises in a more general class of compactifications, though our methods for controlling the corrections to the slow-roll parameters require additional symmetries. We will also discuss closed string versions of our monodromy mechanism in the context of IIB fluxed Calabi-Yau compactifications a la GKP-KKLT.

Martijn Wijnholt

Breaking GUTsin F-Theory

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Shing-Tung Yau

Orbifold and local heterotic flux geometry.

presented with Li-Sheng Tseng