Detailed Agenda

 

Thursday, March 20

• 9-9:45AM - Dan Waldram
Title: "The geometry of N=2 flux backgrounds"
Abstract:
It is well known that for purely gravitational backgrounds, supersymmetry implies special holonomy. I will discuss the corresponding “generalised geometry" of generic supergravity flux backgrounds preserving eight supercharges. We find that supersymmetric backgrounds define new integrable structures on the generalised tangent space, generalising the notion of a Calabi—Yau space.


• 9:45-10:30AM - Chris Hull
Title: "Emergent Time and the M5-Brane"
Abstract:
Issues of space-time signature, emergent dimensions and periodic time are introduced and the possibility of time emerging from a timeless theory are discussed. It is argued that the strong coupling limit of the maximal super-Yang-Mills theory in 5 Euclidean dimensions has an emergent time dimension and gives a description of the 5+1 dimensional M5-brane theory, compactified on a timelike circle. The discussion involves questions of how to quantize Euclidean theories without time.


•10:30-11AM - Magdelena Larfors
Title: "SU(3) structures and heterotic domain wall solutions"
Abstract:
In the absence of background fluxes and sources,  compactifying string theories on Calabi-Yau three-folds leads to supersymmetric solutions. Turning on fluxes, e.g. to lift the moduli of the compactification, generically forces the three-fold to break the Calabi-Yau conditions, and instead fulfill the weaker geometrical condition of having a reduced structure group. In this talk I will discuss manifolds with SU(3) structure from the perspective of heterotic domain wall compactifications.


• 11-11:30AM - Coffee Break

• 11:30AM-12 noon - Fabian Ruehle
Title: “F-Theory duals of heterotic K3 orbifolds”
Abstract: In this talk we investigate the construction of F-theory duals of 6D het- erotic string models compactified on T4/ZN orbifolds which correspond to singular limits of K3. We start by reviewing the duality construc- tion in general and present the approaches that have been used in the smooth case. We then argue why these approaches cannot be used in the singular orbifold case and propose a different way of establish- ing the duality. We provide some consistency checks for this duality construction and argue that F-Theory links all T4/ZN models. This includes orbifold models that have the same ZN modded out but dif- ferent gauge groups as well as orbifolds where different ZN actions have been modded out.

• 12 noon-1:30PM - Lunch in Consulate


• 1:30-2:15PM - Kelly Stelle
Title: " What happens to the Schwarzschild Solution in Quantum Corrected Gravity?"
Abstract:
Inclusion of quadratic curvature terms into the D=4 gravitational action gives rise to a wider class of spherically symmetric static solutions than just the classic Schwarzschild solution of general relativity. At the linearized level, the 1/r potential is modified by the inclusion of Yukawa terms. For a long time, it was not clear what happens to such solutions in the full nonlinear theory, but use of an Israel theorem for the higher-derivative theory now allows this to be understood. The surprising result is that solutions with such Yukawa corrections at spatial infinity do not have horizons. Implications for the structure of black holes will be discussed.

 

• 2:15-3PM - Simon Donaldson
Title: Einstein's equation and algebraic geometry
Abstract:
The lecture will atempt to give an overview of some connections between (the Riemannian version of ) Einstein's equations, several complex variables and algebraic goemetry. we will say something about the long development of this field, through work of calabi, aubin, Yau, Tian and others. We will explain the relevence of the infintie-dimensional geometry of the space of Kahler metrics. In the last part of the talk we will say something about recent work of Chen, Sun and the author in the case of postive Ricci curvature.

• 3-3:30PM - Coffee Break


• 3:30-4PM - Alexander Westphal
Title: "(String) Inflation after BICEP2"
Abstract: BICEP2 from Antarctica has given us the first clear evidence for primordial gravitational waves from inflation causing B-mode polarization at degree angular scales $\ell < 100$. If interpreted in the context of inflation, their signal corresponds to a tensor-to-scalar ratio $r=0.16^{+0.06}_{-0.05}$, which disfavors $r<0.01$ at about $5\sigma$. We will discuss the implications of this result for models of single-field slow-roll inflation. Due to the Lyth bound, the new data represent strong evidence against virtually all small-field models of inflation. We will discuss the need for protective symmetries such as shift symmetries in large-field inflation models which are now favored, and review the situation of string inflation and its large-field version of (axion) monodromy.


• 4-4:30PM - Jean-Luc Lehners
Title: “Cosmic bounces in supergravity”
Abstract: If cosmic bounces can occur, they will play an important role in cosmology, as they will allow for the existence of bouncing cosmologies and will radically modify our ideas about the structure of the universe on the largest scales. However, to date there exists no conclusive evidence yet that cosmic bounces are allowed by fundamental theory. We take a step in this direction by showing that, under certain conditions, non-singular bounces can occur in (old minimal) supergravity. These bounces are free from ghost excitations, despite the fact that the null energy condition is violated during the bounce phase. We also discuss the evolution of cosmological perturbations across such non-singular bounces, demonstrating that (contrary to previous claims in the literature) long-wavelength curvature fluctuations retain a constant amplitude across the bounce.


• 4:30-5PM - Ido Ben-Dayan
Title: ”Probing the Primordial Power Spectrum on Small Scales”
Abstract: The primordial power spectrum encompasses many decades of scales, corresponding to 60 e-folds of inflation. Until now, only about 8 have been observed by CMB and large scale structure observations. In this talk I’ll give a brief overview about current suggestions of prob- ing smaller scales, thus observing more e-folds. This will break the huge degeneracy between different models of inflation leading to a new era in the inflationary paradigm, and potentially for string cosmology as well.

 

• 6:30PM - 8:30PM - Public Lectures

Friday, March 21


• 9-9:45AM - John Ellis
Title: “Inflation in Light of the Planck and BICEP2 Data”
Abstract: The recent data from the Planck satellite and the BICEP2 experiment at the South Pole are compatible qualitatively with the expectations of cosmological inflation, but are in tension with many specific models of inflation. This talk will discuss possibilities for Planck- and BICEP2-compatible models, notably the Starobinsky model, Higgs inflation and scenarios based on supersymmetry and supergravity.

• 9:45-10:30AM - Graham Ross
Title: “Whither SUSY?”
Abstract: To date the LHC has not found evidence for the existence of the new states that are predicted to exist if supersymmetry (SUSY) is to avoid fine tuning, leading to a re-examination of the hierarchy problem and the implications of a Higgs scalar mass of 125 GeV. In the context of SUSY the non-observation of SUSY states may indicate that there are strong correlations between the soft SUSY breaking terms that must be added to the theory. I will discuss how theoretically-well-motivated correlations can lead to a significant increase in the expected mass of the SUSY states without requiring significant fine-tuning and the prospects for testing such schemes.

• 10:30-11AM - Coffee Break

• 11-11:30AM - Sogee Spinner
Title: ”Observing the Neutrino Hierarchy through the Decay of Squark LSPs”
Abstract: An appealing framework for suppressing proton decay in supersym- metry is by considering models with gauged B-L symmetries. This is because R-parity is a subgroup of B-L. The minimal supersymmetric B-L model must violate B-L in such a way to spontaneous break R- parity, but keeps the proton safe. In this context, R-parity violation both generates neutrino masses and allows for the decay of the lightest supersymmetric particle (LSP). This suggests that one can potentially learn about the neutrino sector from collider observations of LSP de- cays. I will briefly introduce this minimal model and discuss how third generation squark LSP decays can reveal information about the neu- trino hierarchy and therefore determine the neutrino masses.


• 11:30AM-12 noon - Lara Anderson
Title: "Geometric Constraints in Heterotic/F-theory Duality"
Abstract:
We systematically analyze a broad class of dual heterotic and F-theory models that give four-dimensional supergravity theories, and compare the geometric constraints on the two sides of the duality. In this talk I will show that F-theory gives new insight into the conditions under which heterotic vector bundles can be constructed. We show that in many cases the F-theory geometry imposes a constraint on the extent to which the gauge group can be enhanced, corresponding to limits on the way in which the heterotic bundle can decompose. We explicitly construct all dual F-theory/heterotic pairs in the class under consideration where the common twofold base surface is toric, and give both toric and non-toric examples of the general results. Finally, we provide evidence for important new aspects of G-flux in four-dimensional compactifications.


• 12 noon-2PM - Lunch outside


• 2-2:45PM - Paul Steinhardt
Title: “The Higgs, the Vacuum, and Geodesic Completeness”
Abstract: We will discuss recent ideas introduced with I. Bars and N. Turok that result in a new type of geodesically complete cosmological solutions in which the Higgs plays an essential role.


• 2:45-3:30PM - Gia Dvali
Title: TBA
Abstract:TBA


• 3:30-4PM - Coffee Break


• 4-4:30PM - Mark Trodden
Title: “Constructing New Scalar Field Theories for Cosmology”
Abstract: I will discuss ghost-free scalar field theories with nonlinear derivative interactions, which may be useful to describe the universe at both early and late times. These theories, often referred to as General- ized Galileons, can be constructed in two interesting ways - through a probe brane technique, or through the method of coset constructions. I will describe the connections between these methods, and how these theories may be useful in cosmology.


• 4:30-5:15PM - Group Discussion of BICEP2 Gravitational Waves Results

 

6:30PM - 8:30PM - Reception in the Consulate


Saturday, March 22


• 9-9:45AM - Michael Douglas
Title: “Low Energy Supersymmetry and the String Landscape”
Abstract: We discuss the prospects for making particle physics predictions based on the string landscape, and particularly the mass scale of superpart- ners. Based mostly on arXiv:1204.6626.


• 9:45-10:15AM- Thomas Grimm
Title: "Studying F-theory Effective Physics using M-theory"
Abstract:
In this talk I will summarize some recent progress in deriving the low-energy effective actions of F-theory in four and six dimensions via M-theory. I will introduce the M-theory to F-theory limit and describe how it can be employed to perform explicit computations. The highlighted conceptional insights are: (1) modifications of the F-/M-theory limit inferred from jumping Chern-Simons terms, (2) derivation of \alpha' corrections from M-theory higher curvature terms, (3) non-perturbative supersymmetry restoration in Spin(7) compactifications of F-theory.


• 10:15-10:45AM - Stefan Groot Nibbelink
Title: “Torus partition functions and spectra of gauged linear sigma models”
Abstract: Worldsheet (0,2) gauged linear sigma models are often used to study supersymmetric heterotic string compactifications with non-trivial vec- tor bundles. We make use of supersymmetric localization techniques to determine their one-loop partition functions. In particular we derive conditions to ensure that the full partition function is modular invari- ant and we propose a computational method to determine the target space matter spectrum.


• 10:45-11:15AM - Coffee Break


• 11:15-11:45AM - Charles Strickland-Constable
Title: "Sphere Reductions and Generalised Geometry"
Abstract:
We present a unified description of maximally supersymmetric flux compactifications as a generalised geometry version of Scherk-Schwarz reduction. In the process, the embedding tensor of the lower-dimensional gauged theory gains a geometrical interpration in the higher-dimensional setup. We show how the "exceptional" sphere reductions fit into this simple picture.

 

• 11:45-12:15AM -Kurt Hinterbichler
Title: "Cosmological Consistency Relations as Ward Identities"
Abstract:
We derive the general consistency relations of single field cosmological correlation functions, which relate (N+1)-point functions with a soft-momentum mode to an N-point function, generalizing Maldacena's original consistency relation for the 3-point function.  These consistency relations arise as Ward identities for an infinite tower of non-linearly realized global symmetries acting on scalar and tensor perturbations.


• 12:15-1:00PM - Lasha Berezhiani
Title: “Slavnov-Taylor Identities for Primordial Perturbations”
Abstract: I will show that all cosmological consistency relations derive from the Slavnov-Taylor identity for spatial diffeomorphisms. Our approach un- derscores the role of diffeomorphism invariance at the root of these relations and offers new insights on the necessary conditions for their validity.