TH Institute on String Phenomenology

21 Jul 2008, 11:00 → 15 Aug 2008, 18:00 Europe/Zurich

TH Theory Conference Room (CERN)

Angel Uranga (CERN), Ignatios Antoniadis (CERN)

String theory remains the best candidate for a fundamental theory of nature, with continuous progress in both the formal and the phenomenological aspects. On the latter, the past few years have provided a drastic improvement on the potential for string theory models to be confronted with low-energy data. The understanding of more general backgrounds for compactification, with spontaneously broken supersymmetry, has provided new insights into the long-standing problems of moduli stabilization and supersymmetry breaking. This progress, along with new techniques in model building have led to important new ideas to address various phenomenological problems in particle physics and early cosmology. The LHC will start running at CERN in summer 2008, triggering a new era of high energy physics, which may uncover physics at the TeV and provide important information about physics at the most fundametal level. It is relevant and timely to compare these outcomes with concrete string models providing fundamental descriptions.

The program has taken advantage of the imminence of LHC and the major string conference being organized at CERN immediately after. The aim of the workshop is to bring together experts in the field and young active researchers, in order to trigger collaborations and define the open avenues to follow in this area.

The scientific programme has been very relaxed, in order to allow the participants to discuss informally and work during their visit. In addition to the already scheduled programme, we encouraged participants interested in a given topic to propose and organize on the spot improvised discussions or seminars.

Monday, 21 July

1 Welcome coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to welcome participants just arriving, and to discuss informally

2 J. Louis: "Compactifications on Generalized Geometries"

I review compactifications on manifolds with SU(3) and SU(3)xSU(3) structure emphasising the structure of the low energy effective action.

Slides louis.pdf

3 A. Micu: "String dualities and manifolds with SU(3) structure"

In this talk I will concentrate on the Heterotic - Type IIA duality when fluxes are turned on. I will show that in a specific case the duality involves M-theory rather than type IIA strings. For this case I will show the construction on the M-theory side which is dual to the heterotic compactifiactions on K3 x T^2 when gauge field fluxes along the torus are considered.

Slides micu.pdf

4 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Tuesday, 22 July

5 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

6 K. Becker: "Torsional heterotic geometries"

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.

Slides becker.pdf

7 P. G. Camara: "Torsion induced soft-breaking terms"

We discuss the conditions for having no-scale solutions of type IIA and IIB supergravity compactified on orientifolds with SU(3) structure. Supersymmetry is spontaneusly broken at tree-level by the effect of the intrinsic torsion. The torsion induced mu-terms in the world-volume of D5, D6 and D9-branes are presented for the particular case of twisted-tori, and the arising patterns of soft-terms are discussed for pure moduli mediation.

Slides camara.pdf

8 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Wednesday, 23 July

9 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

10 D. Lust: "The Landscape of String Theory: Intersecting branes (statistics and collider signatures) and AdS flux vacua

It is known that the number of ground states is very big. This landscape of string vacua contains intersecting brane constructions as well as flux vacua. We will review some of the properties of intersecting branes, like their statistics and possible signatures at the LHC collider. At the end of the talk we are planning to discuss anti-de Sitter flux vacua and transitions between different string vacua by domain walls.

Slides lust.pdf

11 Discussion Coffee

The TH group meets in the discussion room after the colloquium to continue discussion in an informal atmosphere.

Thursday, 24 July

12 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

13 W. Taylor: "Cosmology and particle physics in the type IIA landscape"

The apparently vast landscape of stable and metastable solutions to string theory raises the possibility that string theory may be able to reproduce virtually any reasonable low-energy theory. We describe one corner of the string landscape (IIA) where it seems that the range of possible cosmological models may be more constrained than particle physics.

Slides taylor.pdf

14 G. Shiu: "UV Physics and String Inflation"

Inflation has become the standard paradigm of early universe cosmology. Several outstanding questions in inflationary cosmology, however, require an understanding of the underlying UV physics. In this talk, I will discuss some of these issues and argue how one might turn these UV sensitivities into observational opportunities for string inflation.

Slides shiu.pdf

15 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Friday, 25 July

16 B. Acharya: "Non-thermal Dark Matter and Moduli/Gravitino Problems in M theory"

TBA

Slides acharya.pdf

17 M. Gomez-Reino: "dS vacua and modular inflation in N=1 supergravity and string theory"

I will discuss the possibility of obtaining vacua with spontaneously broken supersymmetry and non-negative cosmological constant in the moduli sector of string models, as well as the possibility of realising slow-roll inflation. I will show that there exist some simple conditions for this to happen which depend only on the Kahler potential. I will then analyse the implications of these conditions through some examples.

Slides gomezreino.pdf

18 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Monday, 28 July

19 Welcome coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to welcome participants just arriving, and to discuss informally

20 R. Blumenhagen: "Instantons in N=1 string compactifications"

In the first part an overview about recent developments on D-brane instantons effects in N=1 string compactifications is given. In the second part new effects based on so-called poly instantons are proposed.

Slides blumenhagen.pdf

21 E. Dudas: "Multi-instanton and one-loop string corrections in toroidal orbifold models

We analyze N=2 perturbative and non-perturbative corrections in type I orbifold models where a dual heterotic description is available. We consider in particular the Bianchi-Sagnotti-Gimon-Polchinski orbifold. By exploiting perturbative calculations of the physical gauge couplings on the heterotic side, we obtain multi-instanton and one-loop string corrections to the K\"ahler potential and the gauge kinetic function. We argue that these corrections are universal in a given class of models where target-space modular invariance holds.

Slides dudas.pdf

22 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Tuesday, 29 July

23 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

24 C. Vafa:"F-theory Meets Phenomenology"

TBA

Slides from String Phenomenology 2008 vafa.pdf

25 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Wednesday, 30 July

26 A. Wingerter: "Orbifolds, the Standard Model, and Unification"

We first highlight some of the (theoretical) shortcomings of the Standard Model, and then consider hints at physics beyond the electroweak scale. Grand Unification and theories in extra dimensions are motivated, and string orbifolds are introduced as ultraviolet completions of these theories. We present a general search strategy for MSSM-like models based on a local SO(10) Grand Unified Theory. The results of our search include 15 models with (i) 3 families of quarks and leptons, (ii) only vectorlike exotics that decouple along D- and F-flat directions, (iii) an exact R-parity, (iv) non-trivial Yukawa matrices, (v) mass hierarchies. Going beyond the "mini-landscape", we answer the question whether the requirement of 3 generations necessarily implies an SO(10) structure. We investigate whether the low-energy values of the coupling constants are compatible with gauge coupling/gravity unification in the heterotic orbifold setup. [Based on arXiv:0706.0217, arXiv:0708.2691, arXiv:0710.4924, arXiv:0805.4186]

Slides wingerter.pdf

27 M. Cvetic: "A string theoretic model of gauge mediated supersymmetry breaking"

Guided by modern String Theory We propose a robust supergravity model of dynamical supersymmetry breaking and gauge mediation. The Polonyi field (and its mirror) is a chiral field, charged under ``anomalous'' U(1)'s, with hierarchical Polonyi-term which can be generated by string instantons, and quartic superpotential terms which arise naturally as a tree-level decoupling effect of massive string states. A stable supersymmetry breaking minimum allows for the realisation of gauge mediation with soft supersymmetry breaking masses at the TeV scale which we realise for a globally consistent SU(5) GUT model of Type I string theory, with an D1-instanton inducing the Polonyi term.

Slides cvetic.pdf

28 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Thursday, 31 July

29 R. Tatar: "New Aspects of Heterotic- F theory duality"

The duality between the Heterotic and F-theory is a powerful tool in gaining more insights into F-theory description of low-energy chiral multiplets. Because chiral multiplets from bundles /\^2 V and /\^2 V^x as well as those from a bundle V are all involved in Yukawa couplings in Heterotic compactification, we need to translate descriptions of all those kinds of matter multiplets into F-theory language through the duality. We find that chiral matter multiplets in F-theory are global holomorphic sections of line bundles on what we call covering matter curves. The covering matter curves are formulated in Heterotic theory in association with normalization of spectral surface, while they are where M2-branes wrapped on a vanishing two-cycle propagate in F-theory.

30 M. Schulz: "String Junctions, Abelian Fibrations, and Flux/Geometry Duality"

The simplest class of flux compactifications, type IIB toroidal orientifolds with N=2 flux, is dual to a class of purely geometric IIA Calabi-Yau compactifications with no flux. Since the duality relates warped and nonwarped compactifications, it has the potential to teach us how to define warped Kaluza-Klein reduction, for which we do not yet have a satisfactory definition. The duality also maps D3 instantons to worldsheet instantons, so it furnishes a check on our understanding of instanton calculus. As a step toward these goals, I will discuss aspects of the duality recently explored in collaboration with Donagi and Gao. The first is an analog of F-theory for T^4 fibrations, which is useful for encoding the dual CY geometry. The second is an analog of D(imenional) duality that relates the CYs to auxiliary surfaces that are simpler to study. As a byproduct, we learn how to construct new Calabi-Yau manifolds with nontrivial fundamental group, which should be useful for heterotic model building.

Slides schulz.pdf

31 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Friday, 1 August

32 V. Braun:"Heterotic Model Building"

I will survey some aspects of geometric compactifications of heterotic strings and their low-energy phenomenology. In particular, I will focus on heterotic "non-standard embeddings". First, I will try to give a brief overview over the role of vector bundles in that construction, and how they can be constructed. Using our "heterotic standard model", I will discuss how the spectrum and Yukawa textures arise. One observation is that not all possible superpotential terms are actually present in such compactifications. For example, I will consider a particular model with one excess Higgs-Higgs conjugate pair. It turns out that flavor-changing neutral currents are greatly suppressed.

Slides braun.pdf

33 K. Dienes: "A New Approach to Flavor?"

The origin of flavor is one of the biggest mysteries of the Standard Model. Despite more than a half-century of data, we still have almost no explanation for family replication in the Standard Model. Many theoretical models can incorporate or accommodate this replication, but very few actually explain/predict/require it. In this talk, I will describe some recent work on a possible new approach towards explaining the origin of family replication in the Standard Model.

34 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Monday, 4 August

35 Welcome coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to welcome participants just arriving, and to discuss informally

36 K. Choi: "Some features of soft terms in flux compactification"

I discuss some features of soft SUSY breaking terms in flux compactification, which include flavor and CP conserving modulus mediation, sequestered uplifting, and the effect of anomalous U(1) symmetry.

Slides choi.pdf

37 H.-P. Nilles: "The Gaugino Code"

Gauginos might 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 energy range for various string theories and various schemes of supersymmetry breakdown and mediation. Three distinct mass patterns emerge.

Slides nilles.pdf

38 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Tuesday, 5 August

39 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

40 B. Ovrut: "Ricci-Flat Metrics and Scalar Laplacians on Calabi-Yau Threefolds"

A mathematical/numerical algrithm is presented for computing Ricci-flat metrics on Calabi-Yau threefolds. This will be explicitly applied to quintics, Z5XZ5 quotients of quintics as well as to the Z3XZ3 threefold of the Heterotic Standard Model. Using these metrics, a procedure is given for explictly calculating the eigenvalue/eigenfunction spectrum of the scalar Laplacian on these Calabi-Yau threefolds.

41 S. de Alwis: "Supersymmetry breaking models and String theory constraints"

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.

Slides dealwis.pdf

42 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Wednesday, 6 August

43 A. Maharana: "Isometries and Approximate Flavor Symmetries in Local Models"

We shall present a mechanism to generate flavor symmetries in local D-brane constructions. The key ingredient shall be approximate isometries of the local geometry. We shall discuss our findings in the context of general arguments for the absence of continuous global symmetries in string compactifications. Implications of the mechanism for the Large Volume Scenario for moduli stabilization will be discussed briefly.

Slides isometries.pdf

44 P. Kumar: "Connecting the LHC with underlying theories"

The talk will discuss some issues in trying to connect underlying theories with data at the LHC; in particular the challenges and the opportunities therein.

Slides kumar.pdf

45 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Thursday, 7 August

46 M. Trapletti: "Toric resolution of Heterotic orbifolds"

We describe how to reproduce a large class of heterotic orbifold models as compactifications of 10d SUGRA on smooth manifolds in the presence of gauge fluxes. We show how to construct the smooth manifolds by resolving the orbifold singularity using toric geometry, and how to consistently embed U(1) gauge fluxes on them. Finally we match the obtained models with the standard heterotic orbifold models.

Slides trapletti.pdf

47 F. Gmeiner: "Millions of Standard Models on Z6'?"

I discuss recent results obtained in collaboration with Gabriele Honecker (arXiv:0806.3039 [hep-th]) on a statistical analysis of standard model-like compactifications on the T^6/Z_6' orbifold in the context of intersecting brane models of type II string theory. In particular the structure of the hidden sector, the gauge coupling constants and chiral exotic matter content is discussed. It turns out that the number of chiral exotics, Higgses and values of gauge couplings are strongly correlated.

Slides gmeiner.pdf

48 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Friday, 8 August

49 M. Bianchi: "D-branes on T-folds with few T's"

Most of the mechanisms for moduli stabilization in String Theory involve R-R fluxes that can only be treated in the supergravity approximation. Non-geometric vacumm configurations with L-R asymmetric `T-duality' twists and shifts allow to stabilize closed string moduli in a controllable way. Peculiarities of bound-states of D-branes in these backgrounds will be discussed in view of phenomenological applications to models with open and unoriented strings.

Slides bianchi.pdf

50 P. Anastasopoulos: "Anomalous U(1)'s at LHC"

I will study an extension of the MSSM by an anomalous abelian vector multiplet and a Stuckelberg multiplet. The anomalies are cancelled by the Green-Schwarz mechanism and the introduction of three-gauge-boson couplings that provide a massive boson like Z' with additional new couplings that have not been considered in the past. I will study the effects of these anomaly related terms and we show that they provide new effects in decays like Z'-> Z photon and Z'-> Z Z showing that in many cases the effects might be visible at LHC.

Slides Anastasopoulos.pdf

51 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Monday, 11 August

52 Welcome coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to welcome participants just arriving, and to discuss informally

53 G. Villadoro: "Status of D6-brane flux models and their effective field theories"

Slides villadoro.pdf

54 S. Raby: "A Fertile Patch in the Heterotic Landscape"

This talk is a follow-up to the talk of Akin Wingerter. I will focus on some of the phenomenological details of one benchmark model discussed in 0708.2691[hep-th].

Slides raby.pps

55 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Tuesday, 12 August

56 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

57 J. Gray: "Uses and methodology of the STRINGVACUA Mathematica package"

I will discuss various applications of the subject of algorithmic algebraic geometry to string phenomenology. In particular i will demonstrate some of the functionality of the recently released STRINGVACUA mathematica package, which facilitates the use of such methods for physicists in our field. Examples will include the analysis of flux vacua and computing Yukawa couplings in smooth, non-standard embedded heterotic compactifications. At the request of some of the participants here, I shall attempt to focus, to some extent, on how these methods actually work rather than providing a comprehensive list of what they can do.

Slides gray.pdf

58 B. Schellekens: "Topics in RCFT orientifolds"

A large set of exact string spectra can be explored using orientifolds of rational conformal field theories. Several results will be discussed, including a variety of ways of realizing the standard model, distributions of physical quantities, free fermionic constructions, neutrino masses and non-supersymmetric, tachyon-free spectra.

Slides schellekens.pdf

59 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Wednesday, 13 August

60 Discussion Session: "The String Landscape"

Discussion led by M. Douglas, B. Schellekens and H. Verlinde on the string theory landscape and its impact on particle physics and cosmology

61 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

62 M. Douglas: "Landscape, low energy supersymmetry, and warping"

A very central question in phenomenology is, what mechanism solves the hierarchy problem. For a long time the only generally accepted solution was low energy supersymmetry. In recent years, other solutions inspired by string theory have been suggested, such as large extra dimensions and warping. Even more recently, the idea that string theory contains a large landscape of solutions, enabling the anthropic solution to the cosmological constant problem, raises the possibilities that the naturalness considerations which prefer some mechanisms over others are modified in string theory, or even that the hierarchy is not the result of a mechanism. We discuss the status of these claims, give a general overview of current thinking about how low energy susy, large extra dimensions and warping can be realized in string compactification, and raise questions whose answers would help us decide whether string theory favors any of these alternatives.

Slides douglas.pdf

63 Discussion Coffee

We meet in the discussion room after the seminars to continue discussion in an informal atmosphere.

Thursday, 14 August

64 J.F. Morales:"Non-perturbative interactions from fluxes"

TBA

Slides morales.pdf

65 F. Marchesano: "Generalized non-supersymmetric flux vacua"

I will discuss an strategy to construct 4D N=0 stable flux vacua of type II string theory, based on the existence of BPS bounds for probe D-branes in some of these backgrounds. In particular, I will consider compactifications where D-branes filling the 4D space-time obey the same BPS bound as they would in an N=1 compactification, while other D-branes, like those appearing as domain walls from the 4D perspective, can no longer be BPS. I will discuss a subfamily of such backgrounds giving rise to 4D N=0 Minkowski no-scale vacua, generalizing the well-known case of type IIB on a warped Calabi-Yau.

Slides marchesano.pdf

66 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.

Friday, 15 August

67 C. Burgess: "Fibre Inflation and Tensor Perturbations in Type IIB Vacua"

The talk presents an inflationary model of inflation in Type IIB string vacua, wherein the inflaton is a Kahler modulus of a K3 fibration Calabi Yau. It arises within the large-volume framework and so is closely related to Kahler modulus inflation models, and shares with these the property that the slow roll is not achieved by tuning parameters in the potential. But unlike the Kahler modulus models it appears to allow the possibility of obtaining observably large primordial tensor fluctuations.

Slides Burgess.pdf Burgess.ppt

68 Discussion Session: Strings vs. LHC

This will be an informal discussion on the status of string theory at the dawn of the LHC, and about the possible impact of coming experimental data.

69 Morning coffee

We meet at 11:00h in the discussion room in front of the TH Secretariat (building 4, second floor), to discuss informally over coffee.