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Workshop Programme

for period 25 - 29 June 2012

String Phenomenology 2012

25 - 29 June 2012

Timetable

Monday 25 June
09:00-09:30 Registration
09:30-09:35 Welcome
09:35-10:10 Allanach, B (University of Cambridge)
  Phenomenological Targets for String Model Builders Sem 1
 

We shall detail points of interest for string model builders coming from recent data, providing some targets that model builders may like to hit. In particular, we shall discuss higgs and supersymmetry searches, and infer some general statements about the spectra and naturalness of models. We shall also mention the t tbar asymmetry from the Tevatron, which disagrees with Standard Model expectations, recent relevant B decay results, Daya bay implications for neutrino masses and mixings and an inferred 130 GeV line in gamma rays coming from our galaxy.

 
10:10-10:45 Acharya, B (Abdus Salam International Centre for Theoretical Physics)
  Generic String/M theory Predictions for Particle Physics and Dark Matter Sem 1
 

Solutions of string/M theory with low energy supersymmetry have moduli fields with masses which are generically of order the mass of the gravitino. This leads to a spectrum of superpartners with squarks and sleptons just beyond the LHC energy scale. Gluinos could however be produced at the LHC and decay with top and bottom rich final states. The mass of the lightest Higgs boson is predicted to be between 122 and 129 GeV. The moduli fields dominate the pre-BBN Universe leading to a non-thermal history which significantly impacts our picture of dark matter, which is predicted to have two components: axions and W-ino like WIMPS. The tentative high energy photon signal in the Fermi-LAT data can be successfully interpreted as the annihilation of these WIMPs into the Z-boson and a photon. Moreover, we demonstrate that this signal is also consistent with an approximately 50% axion component. The axion component implies that experiments like Planck will NOT observe tensor modes in the CMB.

 
10:45-11:20 Morning Coffee
11:20-11:55 Choi, K (Korea Advanced Institute of Science and Technology (KAIST))
  Cosmological moduli problem and double thermal inflation in large volume scenario Sem 1
11:55-12:30 Berenstein, D (University of California, Santa Barbara)
  Open string axions and the flavor problem Sem 1
 

I will describe some bottom up models of particle physics inspired by D-brane phenomenology that address aspects of the flavor problem. I will argue that many of these models lead to an axion arising from open string modes that sometimes falls within the allowed axion window. The phenomenology of these axion models can rule out many models of physics beyond the standard model. A satisfactory solution of the flavor problem seems to produce models that deconstruct extra dimensions.

 
12:30-13:30 Lunch at Wolfson Court
14:00-14:35 Cicoli, M (Abdus Salam International Centre for Theoretical Physics)
  Cosmology and Moduli Stabilisation for Chiral Global Models Sem 1
 

I will present recent results which try to combine moduli stabilisation and chiral model building both in the geometric regime and at the quiver locus within a fully consistent type IIB string compactification described in terms of toric geometry. I will also briefly discuss some cosmological applications and a new way to get dS vacuua in a manifestly supersymmetric effective action.

 
14:35-15:10 Goodsell, M (CERN)
  Looking for the LARGE volume axiverse Sem 1
 

An "axiverse" is a generic prediction of string theory, although the axions are typically extremely hard to detect, and sometimes may not actually solve the strong CP problem. I shall discuss how the axiverse is realised in the LARGE volume scenario, including what the axion couplings are, whether they can be detected, how the QCD axion can arise - and also how to build models with an additional axion-like particle that could explain some intriguing astrophysical anomalies.

 
15:10-15:45 Redondo, J (Max-Planck-Institut für Physik, München)
  Weakly interacting slim particles in astrophysics, cosmology and the laboratory Sem 1
 

Weakly interacting slim particles (WISPs) appear often in extensions of the standard model, string theory in particular. This is the case of pseudo Nambu Goldstone Bosons, stringy axions, moduli, hidden photons, mini-charged particles and a long etc. The strongest bounds on their existence come frequently from cosmology and astrophysics but, in particular cases, laboratory experiments at the low energy, high intensity frontier, are more relevant. In this talk we review the most relevant astro/cosmo arguments and laboratory experiments used to constrain the existence of WISPs, focusing on the most discussed cases of axion-like particles (ALPs) and Hidden Photons. We will also pay attention to the recent anomalies which could be pointing to the existence of WISPs: the anomalous cooling rate of white dwarfs and the transparency of the Universe to gamma-rays. Finally, we will conclude discussing WISPs as testable cold dark matter candidates.

 
15:45-16:20 Afternoon Tea
16:20-16:55 Luest, D (Max-Planck-Institut für Physik, München)
  Non-commutative/non-associative geometry and effective actions of non-geometric string backgrounds Sem 1
16:55-17:30 Blumenhagen, R (Max-Planck-Institut für Physik, München)
  Strings in Non-geometric Backgrounds Sem 1
 

We consider closed bosonic string theory with flat background and constant H-flux. Up to linear order in the flux, this is a solution to the string equations of motion and we are able to define a world-sheet conformal field theory framework to compute scattering amplitudes. In the easiest cases of n-point tachyon amplitudes, we use the properties of the Rogers dilogarithm function to speculate about the nature of the product of functions on spacetimes T-dual to the original configuration.

 
17:30-18:45 Drinks Reception
18:45-19:15 Dinner for Residents at Fitzwilliam & Churchill Colleges
Tuesday 26 June
09:00-09:35 Raby, S (Ohio State University)
  SU(6) orbifold GUT on M4 x RP2 : Gauge - Higgs unification Sem 1
 

In a recent paper we constructed an SU(6) N=2 SUSY model in 6 dimensions. We discuss gauge and SUSY breaking via orbifolding and/or Wilson lines. The model has gauge-Higgs unification. We calculate the GUT scale threshold corrections to gauge coupling unification.

 
09:35-10:10 Ratz, M (Technische Universität München)
  Supersymmetric unification and R symmetries Sem 1
 

After reviewing some virtues and problems of the minimal supersymmetric standard model (MSSM), I will show that, if one demands anomaly freedom and fermion masses, only R symmetries can forbid the supersymmetric Higgs mass term mu. I will then prove that R symmetries are not available in conventional grand unified theories (GUTs) and argue that this prevents natural solutions to the doublet-triplet splitting problem in four dimensions. On the other hand, higher-dimensional GUTs do not suffer from this problem. I will briefly discuss an explicit string-derived model in which the mu and dimension five proton decay problems are solved by an order four discrete R symmetry, and comment on the higher-dimensional origin of this symmetry.

 
10:10-10:45 Nilles, P (Universität Bonn)
  The Zip Code of Quarks, Leptons and Higgs Bosons Sem 1
 

The location of particles in extra dimensions determines the properties of the 4-dimensional low-energy effective action, such as Yukawa couplings and the pattern of supersymmetry breakdown. We analyze these questions in the framework of the heterotic MiniLandscape.

 
10:45-11:20 Morning Coffee
11:20-11:55 Nelson, B (Northeastern University)
  An Algorithmic Method for Identifying Swiss Cheese Manifolds Sem 1
 

We describe an efficient algorithmic test for the Swiss Cheese property in Calabi-Yau threefolds, which is typically considered in the context of moduli stabilization in Large Volume Scenarios of type~IIB flux compactifications of string theory. The algorithm recasts the issue of moduli stabilization at large volume into the language of algebraic geometry, thereby allowing for a large scale computational analysis. Preliminary results of a scan of Calabi-Yau three folds with small Hodge numbers will be presented.

 
11:55-12:30 Kane, G (University of Michigan)
  Compactified string/M theory prediction of the Higgs boson mass and properties. Sem 1
12:30-13:30 Lunch at Wolfson Court
14:00-14:15 Andriot, D (Ludwig-Maximilians-Universität München)
  Non-geometric fluxes in higher dimensions: I Sem 1
 

Non-geometric fluxes appear in four-dimensional gauged supergravities through specific terms in the potential. These terms are of phenomenological interest for the matters of moduli stabilization or de Sitter solutions. Unfortunately, their ten-dimensional origin, and their relation to non-geometry, remain unclear. In this talk, I will present recent progress on these questions. Thanks to a field redefinition in ten-dimensional supergravity, one makes the non-geometric Q and R fluxes appear, and additionally restores a standard notion of geometry. A dimensional reduction can then be performed, and the four-dimensional non-geometric terms of the scalar potential are recovered.

 
14:00-14:15 Sumitomo, Y (Hong Kong University of Science and Technology)
  A Stringy Mechanism for A Small Cosmological Constant Sem 2
 

We propose a simple stringy mechanism that prefers metastable vacua with a small cosmological constant. We argue the generic probability distribution for the metastable vacua which peaks with a divergent behavior at the zero value of cosmological constant. Then we illustrate this in a model of type IIB string theory, though the suppression in the model is modest.

 
14:15-14:30 Patalong, P (Max-Planck-Institut für Physik, München)
  Non-geometric fluxes in higher dimensions: II Sem 1
 

It has been shown that non-geometric fluxes appear in ten-dimensional supergravity by performing a field redefinition. Following a similar strategy in double field theory surprisingly allows for a geometric interpretation of these fluxes. More precisely, the Q-flux appears as part of a dual curvature scalar, reminiscent of the geometric flux f. The R-flux turns out to be a tensor and appears in the same way as the usual H-flux does. Solving the strong constraint connects this formalism to the ten-dimensional approach. Furthermore, some recent lifts of four-dimensional gauged supergravity to double field theory can be matched.

 
14:15-14:30 Ohta, N (Kinki University)
  Accelerating Universes in String Theory via Field Redefinition Sem 2
 

We study cosmological solutions in the effective heterotic string theory with \alpha'-correction terms in string frame. It is pointed out that the effective theory has an ambiguity via field redefinition and we analyze generalized effective theories due to this ambiguity. We restrict our analysis to the effective theories which give equations of motion of second order in the derivatives, just as ``Galileon" field theory. This class of effective actions contains two free coupling constants. We find de Sitter solutions as well as the power-law expanding universes in our four-dimensional Einstein frame. The accelerated expanding universes are always the attractors in the present dynamical system.

 
14:30-14:45 Smyth, P (EPFL - Ecoles Polytechniques Fédérales de Lausanne)
  Spontaneous Partial Supersymmetry Breaking Sem 1
 

I will review some recent work on spontaneous partial supersymmetry breaking in extended supersymmetry. I will first describe the no-go theorems which forbid N=2 to N=1 spontaneous supersymmetry breaking in global and local supersymmetry, before showing how they are circumvented. I will then discuss some new techniques involving the embedding tensor formalism which allow us to study this problem systemically and find the low-energy effective theory in the N=1 vacuum. This leads to interesting insights into spontaneous partial supersymmetry breaking in supergravity and string theory, as well as new results in quaternionic geometry.

 
14:30-14:45 Kim, SA (Asia Pacific Center for Theoretical Physics)
  N-flation and No-boundary measure Sem 2
 

In this talk, I will give a brief review on N-flation models. Moreover, I will present the recent work of N-flation with no-boundary condition which is one of several ways to avoid the singularities of our very early Universe. Even though no-boundary measure disfavours the histories of large e-foldings in inflation, we show another way to lift up the probability of inflationary histories without considering any other factors, but with the large number of fields such as N-flation fields.

 
14:45-15:00 Break
15:00-15:15 Plauschinn, E (Universiteit Utrecht)
  Bianchi identities for non-geometric fluxes from Palatini-Lovelock-Cartan gravity Sem 1
 

Flux compactifications are an important building block for obtaining (semi-)realistic string theory vacua. Conventional H- and geometric flux are rather well-understood in this setting, however, non-geometric fluxes are understood to a far lesser degree.

In this talk, it is first reviewed how certain fluxes can be treated as the torsion of a connection, and how gravity theories can be formulated via the Palatini formalism. Next, this formalism is extended to higher orders in the curvature leading to constraints on the fluxes, which are then interpreted as Bianchi identities.

 
15:00-15:15 Rummel, M (Universität Hamburg)
  De Sitter vacua in type IIB / F-theory by Kahler uplifting Sem 2
 

We derive a sufficient condition and present explicit examples based on toric geometry for realizing meta-stable de Sitter vacua with small positive cosmological constant within type IIB string theory / F-theory flux compactifications with spontaneously broken supersymmetry. There are a number of `lamp post' constructions of de Sitter vacua in type IIB string theory and supergravity. We show that one of them -- the method of `K\"ahler uplifting' by F-terms from an interplay between non-perturbative effects and the leading $\alpha'$-correction -- allows for a more general parametric understanding of the existence of de Sitter vacua. The result is a condition on the values of the flux induced superpotential and the topological data of the Calabi-Yau compactification, which guarantees the existence of a meta-stable de Sitter vacuum if met. Our analysis explicitly includes the stabilization of all moduli, i.e. the K\"ahler, dilaton and complex structure modu li, by the interplay of the leading perturbative and non-perturbative effects at parametrically large volume.

 
15:15-15:30 Lee, S-J (Korea Institute for Advanced Study (KIAS))
  Heterotic bundles on toric Calabi-Yau manifolds Sem 1
 

We undertake a systematic scan of vector bundles over the database of torically generated Calabi-Yau three-folds in the context of heterotic string compactifications. Specifically, we construct positive monad bundles over Calabi-Yau hypersurfaces in toric varieties, with the number of Kahler moduli equal to one, two and three, and extract physically interesting models. We select models which can possibly lead to three families of matter after quotienting by a freely-acting discrete symmetries and including Wilson lines. About 2000 such models on two manifolds are found.

 
15:15-15:30 Turzynski, K (Uniwersytet Warszawski)
  Multi-field inflationary trajectories with a fast-turn feature Sem 2
 

We study models of multi-field inflation in which the inflationary trajectory contains a strong bending occurring when the observable scales are still inside the Hubble radius. We discuss the impact of such a fast-tirn feature on the dynamics of the inflationary perturbations - and the traces such an event may leave in the power spectrum of curvature perturbations.

 
15:30-15:45 Klaput, M (University of Oxford)
  Bundles over Nearly-Kahler Homogeneous Spaces in Heterotic String Theory with Flux Sem 1
 

String compactifications incorporating non-vanishing H-flux have received increased attention over the past decade for their potential relevance to the moduli stabilization problem. Their internal spaces are in general not Kähler and, therefore, not Calabi-Yau. In the heterotic string an important technical problem is to construct gauge bundles on such spaces. I will present a method of how to explicitly construct gauge bundles over homogeneous nearly-Kähler manifolds of dimension six. These bundles solve the heterotic string including first order alpha' corrections and allow for non-vanishing flux. I will also discuss some of the arising implications for model building.

Related Links •http://arxiv.org/abs/1107.3573 - presented results are based on this paper

 
15:30-15:45 Zavala, I (Rijksuniversiteit Groningen)
  Lifshitz Solutions in String Theory Sem 2
 

I will discuss solutions with Lifshitz scaling within string supergravity for an arbitrary scaling parameter z. After showing how to construct exact Lifshitz spacetimes, I will discuss more general solutions, including black holes with Lifshitz asymptotics.

 
15:45-16:15 Afternoon Tea
16:15-16:30 Kraus, S (Universität Heidelberg)
  Fluxbrane Inflation Sem 1
 

Fluxbrane inflation (arXiv:1104.5016) is a recently proposed stringy realisation of D-term hybrid inflation, featuring some appealing phenomenological characteristics. In contrast to other brane inflation models, fluxbrane inflation has a naturally flat inflaton potential at leading order and thus does not rely on strong warping or an extremely anisotropic compact space. Additionally, the scenario contains a mechanism which allows one to avoid the clash with observational bounds due to cosmic string production rather easily. In my talk, I will present the most interesting aspects of the model and, furthermore, discuss recent progress and new challenges regarding moduli stabilisation (in the context of the LARGE volume scenario) as well as the impact of higher-order corrections on the flatness of the inflaton potential.

 
16:15-16:30 Torabian, M (Abdus Salam International Centre for Theoretical Physics)
  On Asymptotically de Sitter Space: Entropy & Moduli Dynamics Sem 2
 

I will discuss what the present state of the universe, as an asymptotically de Sitter space, tells us about the moduli dynamics in the very early universe. This study is inspired by entropy counting and holographic bounds.

 
16:30-16:45 Moniz, P (Universidade da Beira Interior)
  (New) Borders for Quantum Cosmology Sem 1
 

Quantum Cosmology tackles the quantum description of the early universe. It is aimed as an accessible primer that covers the basics, critically discussing ideas and concepts that comprise our current knowledge. The scope for analyzing quantum cosmological models within a supersymmetric framework is pointed.

As much as possible, it summarizes what we know, what we think we know and what we think we do not know on an equal footing. It is focused for ‘young’, inquisitive minds eager to embark on in-depth research in this field. It is hoped to suggest the tools researchers will need to go on their own, pushing them to ask the right questions rather than seek definitive answers.

 
16:30-16:45 Walters, W (University of Liverpool)
  SO(10) Resolutions in F-theory Sem 2
 

We discuss SO(10) GUTs in F-theory, starting with the Tate form for a D5 singularity, and resolving. We then look at codimension two and three singularities to get matter and Yukawa couplings.

 
16:45-17:00 Wills, D (University of Durham)
  Stringy Origins of Cosmic Structure: The D-brane vector curvaton Sem 1
 

I will discuss how the U(1) vector fields that live on the worldvolumes of D-branes in Type IIB string theory may play the role of vector curvatons and hence give rise to distinctive features in the spectrum and bispectrum of the curvature perturbation. I will first consider vector fields on D3-branes in open-string inflation, as a means of illustrating the principle. I will then discuss a D7-brane vector curvaton scenario in closed-string inflation.

 
16:45-17:00 Kerstan, M (Universität Heidelberg)
  Fluxed M5-instantons in F-theory Sem 2
 

We discuss the partition function of M5-instantons in F-theory, focussing in particular on vertical M5-instantons that describe the uplift of Type IIB E3-instantons. This duality allows us to determine the partition function of the M5-instanton, which is non-trivial to obtain directly in M-theory.

 
17:00-17:15 Break
17:15-17:30 Lüdeling, C (Universität Bonn)
  Anomalies and Remnant Symmetries in Heterotic Constructions Sem 1
 

First I discuss anomalies in heterotic compactifications. I argue that anomalies will generically not be universal, and illustrate this point by an explicit example of a heterotic orbifold blowup. Then, I investigate the origin of discrete (R and non-R) symmetries on smooth Calabi-Yau manifolds via an GLSM approach.

 
17:15-17:30 McGuirk, P (Cornell University)
  Hidden-sector current-current correlators in holographic gauge mediation Sem 2
 

I will discuss gravity duals of the gauge mediation of supersymmetry breaking. In particular, I will discuss how the tools of AdS/CFT can be used to calculate certain two-point functions in the hidden sector which, via the formalism of general gauge mediation, can be related to soft terms in the visible sector.

 
17:30-17:45 Savelli, R (Max-Planck-Institut für Physik, München)
  Flux Quantization in F-theory and Freed-Witten Anomaly Sem 1
 

Using M/F-theory duality, I will relate the quantization of the G-flux in M-theory to the one of the gauge flux on type IIB D7-branes prescribed by Freed-Witten anomaly cancellation. The correspondence is shown for all unitary and symplectic Kodaira singularities, by explicitly constructing appropriate 4-cycles in the M-theory elliptic fourfold, which are able to detect the global anomaly.

 
17:30-17:45 Sanz Cillero, JJ (Istituto Nazionale di Fisica Nucleare, Bari)
  One-Loop Calculation of the Oblique S Parameter in Higgsless Electroweak Models Sem 2
 

If the Higgs boson does not show up soon, we should look for alternative mechanisms of mass generation, satisfying the many experimental constraints which the Standard Model (SM) has successfully fulfilled so far. Following this aim, we present a one-loop calculation of the oblique S parameter within Higgsless models of Electroweak Symmetry Breaking (EWSB) and analyze the phenomenological implications of the available electroweak precision data. By means of an effective Lagrangian we implement the chiral symmetry breaking SU(2)_L x SU(2)_R -> SU(2)_(L+R) with Goldstones, gauge bosons and one multiplet of vector and axial-vector massive resonance states. Using the dispersive representation of Peskin and Takeuchi and imposing the short-distance constraints dictated by the operator product expansion, we obtain S at the next-to-leading order in terms of a few resonance parameters. We have found that, in order to match the experimental determination of the S parameter, the res onance masses are required to be over the TeV scale in this kind of strongly-coupled EWSB scenarios.

 
17:45-18:00 Svanes, E (University of Oxford)
  Moduli Stabilisation of Heterotic String Theory with Flux Sem 1
 

I will discuss the next to leading order corrections to the heterotic bundle constructions of Klaput, Lukas and Matti. I will show how these constructions lead to a non-zero H-flux at next to leading order, and how this flux may be used to stabilise either the dilaton, or the volume of the internal space. I will then add a gaugino condensate to the 4D supergravity, and show that for certain bundle choices it is possible to stabilise all moduli at consistent values.

 
17:45-18:00 Mehta, V (University of Liverpool)
  String--derived models and light U(1) embeddings Sem 2
 

Extra U(1) extensions of the Standard Model arising from string theory have been considered in the literature since the mid-80s. Such a U(1) can play an important phenomenological role in solving the \mu problem and suppressing other unwanted operators, such as dimension four and five proton decay mediating operators. Yet keeping the U(1) unbroken down to low scales in quasi-realistic string models turns out to be highly non-trivial. In this talk I will discuss the constraints and some scenarios in which they may be alleviated.

 
18:00-18:15 Mehta, D (Syracuse University)
  Numerical Algebraic Geometry: A New Perspective on String and Gauge Theories Sem 1
18:45-19:15 Dinner for Residents at Fitzwilliam & Churchill Colleges
Wednesday 27 June
09:00-09:35 Shiu, G (University of Wisconsin-Madison)
  Searching for de Sitter vacua in String Theory Sem 1
09:35-10:10 Graña, M (CEA/Saclay)
  Anti-branes in Klebanov-Strassler: to be or not to be? Sem 1
 

Anti-branes in the deformed conifold are used for example to construct de Sitter vacua. In the probe approximation, they lead to a metastable state. I will present work done over the last three years to go beyond the probe approximation by taking into account the back-reaction of the anti-branes. To be, or not to be (a metastable state), that is the question. We are pinning down the answer.

 
10:10-10:45 McAllister, L (Cornell University)
  The Wasteland of Random Supergravities Sem 1
 

We show that in a general N=1 supergravity with N >> 1 scalar fields, an exponentially small fraction of the de Sitter critical points are metastable vacua. Taking the superpotential and Kahler potential to be random functions, we construct a random matrix model for the Hessian matrix, which is well-approximated by the sum of a Wigner matrix and two Wishart matrices. We compute the eigenvalue spectrum analytically from the free convolution of the constituent spectra and find that in typical configurations, a significant fraction of the eigenvalues are negative. Using Coulomb gas techniques, we then determine the probability P of a large fluctuation in which all the eigenvalues become positive. Strong eigenvalue repulsion makes this extremely unlikely: we find P \propto exp(-c N^2), with c a constant, for generic critical points. Our results have significant implications for the counting of de Sitter vacua in string theory, but the number of vacua remains vast.

 
10:45-11:20 Morning Coffee
11:20-11:55 Westphal, A (Deutsches Elektronen-Synchrotron)
  Tensor modes on the string theory landscape Sem 1
 

We attempt an estimate for the distribution of the tensor mode fraction $r$ over the landscape of vacua in string theory. The dynamics of eternal inflation and quantum tunneling lead to a kind of democracy on the landscape, providing no bias towards large-field or small-field inflation regardless of the class of measure. The tensor mode fraction then follows the number frequency distributions of inflationary mechanisms of string theory over the landscape. We show that an estimate of the relative number frequencies for small-field vs large-field inflation, while unattainable on the whole landscape, may be within reach as a regional answer for warped Calabi-Yau flux compactifications of type IIB string theory.

 
11:55-12:30 Antoniadis, I (CERN - European Organisation for Nuclear Research)
  String mass hierarchies and experimental predictions Sem 1
12:30-13:30 Lunch at Wolfson Court
14:00-14:35 Gray, J (Ludwig-Maximilians-Universität München)
  Calabi-Yau and Non-Calabi-Yau backgrounds for heterotic phenomenology Sem 1
 

I will discuss various aspects of model building and moduli stabilization in heterotic string theory. This will include building standard models from pure abelian gauge field configurations, and investigating compactifications on manifolds admitting SU(3) structures with intrinsic torsion.

 
14:35-15:10 Anderson, L (Harvard University)
  Vector Bundles and Moduli Stabilization in Heterotic Theories Sem 1
 

I will discuss recent work on moduli stabilization without Neveu-Schwarz three-form flux in Calabi-Yau compactifications of Heterotic M-theory. In particular, I discuss a systematic approach to stabilizing the complex structure moduli in heterotic vacua and how the holomorphic deformations of the gauge bundle can naturally lead to the consideration of multiple Calabi-Yau threefolds, connected by geometric transitions.

 
15:10-15:45 Vafa, C (Harvard University)
  Reflections on F-theory Phenomenology Sem 1
15:45-16:15 Afternoon Tea
16:15-16:30 Kumar, P (Columbia University)
  Mixed Wino-Axion Dark Matter in String/M Theory and the 130 GeV gamma-line "Signal" Sem 1
 

String/M theory compactifications with low energy supersymmetry tend to predict that dark matter has two components: axions and WIMPs \cite{1004.5138,1204.2795}. In accord with this, we show that the tentative 130 GeV gamma-line signal reported in \cite{1204.2797} can be interpreted as arising from the annihilation of 145 GeV mass, Wino-like WIMPs into a Z-boson and a photon. In this context, the signal implies a second component of dark matter which we interpret as being composed of axions - the relative Wino/Axion abundances being approximately equal. Further predictions are implied: signals in both diffuse and monochromatic photons from dwarf spheroidal galaxies; monochromatic photons with energy 145 GeV; for the LHC, the Higgs boson mass has been predicted in this framework \cite{1112.1059}, and the current Higgs limits provide interesting constraints on the mass of the Gluino.

 
16:15-16:30 Roest, D (Rijksuniversiteit Groningen)
  The Conifold's Competing Condensates Sem 2
 

We discuss holographic superconductivity in the context of IIB on AdS_5 x T^{1,1}. In the spectrum on the gravity side, there are several modes with potential instabilities. In addition to the one identifed by Gubser et al, we point out that there is another, potentially more unstable mode. Moreover, we propose a concrete model for the dynamics of this mode. With this proposal at hand, we show that it indeed dominates the thermodynamics at low temperatures.

 
16:30-16:45 Watson, S (Syracuse University)
  How UV sensitive is inflation? Sem 1
 

We investigate the validity of effective field theory methods and the decoupling of heavy fields during inflation. Considering models of inflation in which the inflaton is coupled to heavy degrees of freedom, we find that violations of decoupling are absent unless there is a breakdown of the slow-roll conditions. Next we allow for a temporary departure from inflation resulting in a period of non-adiabaticity during which effective field theory methods are known to fail. We find that the locality of the event and energy conservation lead to a tight bound on the size of the effects of the heavy field.

 
16:30-16:45 Deser, A (Max-Planck-Institut für Physik, München)
  Quasi- Poisson structures, Courant algebroids and Bianchi identities for non-geometric fluxes Sem 2
 

The notion of non-geometric flux was introduced in string theory to correctly describe the degrees of freedom in four-dimensional effective superpotentials of type II flux compactifications. Whereas the H-flux is simply the field strength of the NS-NS B-field and the f-flux can be interpreted as the structure constants of a non-holonomic basis of the tangent bundle, the physical and mathematical properties of the remaining Q- and R-fluxes are to a great extent unknown. In this talk, we will first use the notion of a (quasi-)Poisson structure to re-derive directly on the tangent bundle the commutation relations containing all four fluxes as structure constants. As a consequence, we get Bianchi-type identities for the fluxes by writing down the Jacobi-identities for the algebra. Using these Bianchi-identities and the theory of quasi Lie-algebroids, we are able to identify the associated Courant algebroid structure, which is essential for dealing with all fluxes being non-zero.

 
16:45-17:00 Lu, R (University of Michigan)
  Collider Phenomenology of String/M Theory Sem 1
 

Very generic string/M theory assumptions can lead to non-trivial phenomenologies that can be tested at the LHC. The branching fraction to the 3rd family quarks of the gluino decay should be enhanced, leading to multi-lepton and/or multi-bjet signatures. On the other hand, chargino could have long enough lifetime to produce disappearing tracks in the detector.

 
16:45-17:00 Halverson, J (University of Pennsylvania)
  Moduli Dependence of M5-instantons in F-theory Sem 2
 

M5-instanton corrections to the superpotential in four-dimensional F-theory compactifications have a moduli-dependent prefactor which contains interesting physical content. In two examples obtained via heterotic duality, I will show that the entire vanishing locus of the prefactor can be understood via simple F-theory physics, often occurring at enhanced symmetry points in the complex structure moduli space. If time permits, I will discuss the relationship between line bundle cohomology on a distinguished curve in the instanton worldvolume and the intermediate Jacobian of the M5-instanton.

 
17:00-17:15 Break
17:15-17:30 Davies, R (University of Oxford)
  Dirac gauginos and unification in F-theory Sem 1
 

In the MSSM, the gauginos are assumed to acquire Majorana masses after supersymmetry breaking. If the light spectrum is extended slightly to include chiral multiplets in the adjoint representation of the gauge group, they can instead acquire Dirac masses by pairing up with the fermionic components of these multiplets. Dirac gauginos have several interesting properties, not least that they can be significantly heavier than Majorana gauginos, without paying any price in naturalness; this becomes particularly interesting in the light of the null results of the 2011 LHC searches for superpartners. One good reason for a theory to contain Dirac gauginos is if it has an unbroken (approximate) R-symmetry. In string theory, the construction of models with adjoint chiral fields and (optionally) an unbroken R-symmetry poses different problems to constructing the MSSM, especially as the gauge couplings no longer unify unless further matter is present. I will discuss solutions to some of these problems within the context of F-theory.

 
17:15-17:30 Cleaver, G (Baylor University)
  Systematic Investigations of the Heterotic String Landscape Sem 2
 

Results are reviewed for the first stages of Baylor University’s ongoing systematic statistics investigations of the parameter space of free fermionic heterotic string models. Presented is the complete set of D = 4, 6 models with either maximal or completely broken spacetime SUSY that are constructed from the untwisted sector and exactly one additional gauge sector containing anywhere from order 2 through 32 twists. All additional models generated to date with additional twisted gauge sectors are also discussed. A vast degeneracy among models appears: from the roughly 2 billion D = 4 models with a single twist sector, only 577 physically distinct models appear. 68 of these have N = 4 SUSY and 509 have completely broken SUSY. To date, no new physically distinct models appear among any of those formed from two or more twisted gauge sectors. Several redundancies among D= 4 models and among D= 6 models are proven to result from redundancies already present among D= 10 models . Methods to reduce redundancies in D= 4, 6 systematic searches are summarized. Statistics regarding the appearance of various combinations of gauge group factors and of GUT groups among the set of 577 physically unique models are presented. Lastly, moving briefly to models with matter sectors, a model with an even number D of large space-time dimensions is shown to always have maximal SUSY, if it is formed from the untwisted sector and a sector with a massless left-mover and an odd ordered right-mover.

 
17:30-17:45 Khalil, S (Zewail City of Science and Technology)
  TeV scale SUSY B-L Sem 1
 

We propose a scheme where the three relevant physics scales related to the supersymmetry, electroweak, and baryon minus lepton (B-L) breakings are linked together and occur at the TeV scale. The phenomenological implications in the Higgs and leptonic sectors are discussed.

 
17:30-17:45 Jurke, B (Northeastern University)
  Scanning for Swiss Cheese geometries Sem 2
 

Moduli stabilization in the Large Volume Scenario requires a specific kind of six-dimensional Calabi-Yau geometry for the compactification procedure, which is being referred to as "Swiss Cheese" due to the presence of certain holes for instanton wrappings. Only a handful of such manifolds are known explicitly. I will give an overview of the Large Volume Scenario and present recent progress on a general scan of the Calabi-Yau threefold landscape for the Swiss Cheese property.

 
17:45-18:00 Ruiz Cembranos, JA (Universidad Complutense de Madrid)
  p-adic Strings at Finite Temperature Sem 1
 

We study the finite temperature theory of p-adic string models. We analyze the partition function and main thermodynamic properties arising from perturbative thermal loops. We find that the thermal properties of these non-local field theories can be interpreted either as contributions of standard thermal modes with energies proportional to the temperature, or inverse thermal modes with energies proportional to the inverse of the temperature, leading to a thermal duality at leading order analogous to the well known T-duality of string theory.

 
17:45-18:00 Heidenreich, B (Cornell University)
  Orientifolds and new N=1 Dualities Sem 2
 

I report on a new class of N=1 dualities relating different gauge theories arising from D3 branes probing orientifold singularities. These dualities provide new, nontrivial solutions to the 't Hooft anomaly matching conditions. I discuss an infinite class of orbifold singularities where the duality can be interpreted as S-duality in ten dimensions. I also discuss non-orbifold singularities, and the microscopic interpretation of the duality in terms of an orientifold transition between compact O7+ and O7- planes.

 
18:45-19:15 Dinner for Residents at Fitzwilliam & Churchill Colleges
Thursday 28 June
09:00-09:35 Cvetic, M (University of Pennsylvania)
  Type II and F-theory Instanton Effects Sem 1
 

We address D-instanton contributions to the non-perturbative superpotential in Type II and F-theory, employing multi-pronged approaches, including heterotic and M-theory dualities. We focus focus on the determination of instanton zero modes and their contributions to the superpotential Pfaffian structure.

 
09:35-10:10 Grimm, T (Max-Planck-Institut für Physik, München)
  Fluxes and Warping in F-theory Sem 1
 

We discuss the effective theory of F-theory compactifications by using the M-theory dual. Two main results are highlighted: (1) the chiral index of a 4D F-theory compactification can be determined by four-form flux when comparing 3D Chern-Simons theories at one loop, (2) the inclusion of warping effects due to fluxes in M-theory is crucial to determine corrections to the F-theory effective theory even if in the latter warping effects can be neglected.

 
10:10-10:45 de Alwis, S (University of Colorado)
  Dark Matter density and the Higgs mass in LVS String Phenomenology. Sem 1
10:45-11:20 Morning Coffee
11:20-11:55 Marchesano, F (IFT-UAM/CSIC)
  Yukawas in F-Theory Sem 1
11:55-12:30 Palti, E (Centre de Physique Théorique de l’Ecole Polytechnique (CPHT))
  Wavefunctions and local models in F-theory Sem 1
 

I will discuss general aspects of wavefunctions and their overlaps in local F-theory models with an aim towards developing the ideas of ultra local model building.

 
12:30-13:30 Lunch at Wolfson Court
14:00-14:35 Schafer-Nameki, S (King's College London)
  F-theory and G-flux Sem 1
14:35-15:10 Weigand, T (Universität Heidelberg)
  Gauge fluxes and M5-instantons in F-theory and their Type IIB duals Sem 1
 

I discuss recent progress in the description of G4 gauge fluxes in F-theory compactifications on Calabi-Yau fourfolds. Such fluxes are important from the perspective of F-theory model building, where gauge fluxes are required for example for the generation of chiral matter. An explicit dictionary between a class of factorisable G4 fluxes in certain F-theory compactifications and corresponding diagonal U(1) fluxes in Type IIB orientifolds sheds new light on the uplift of Type IIB vacua to F-theory. This global description of gauge fluxes in F-theory also allows for the evaluation of selection rules for M5-instantons to contribute to the superpotential.

 
15:10-15:45 Uranga, A (IFT-UAM/CSIC)
  Non-abelian discrete gauge symmetries in string theory Sem 1
 

I will discuss the realization of non-abelian discrete gauge symmetries in field theory and string theory, and present several classes of string models exhibiting non-abelian discrete gauge symmetries. In models of magnetized/intersecting D-branes, the discrete symmetries impose non-trivial constraints on Yukawa couplings, and correspond to interesting flavour symmetries in MSSM-like models.

 
15:45-16:15 Afternoon Tea
16:15-16:30 Groot Nibbelink, S (Ludwig-Maximilians-Universität München)
  Super Weyl invariance: BPS equations from heterotic worldsheets Sem 1
 

It is well-known that the beta functions on a string worldsheet correspond to the target space equations of motion, e.g. the Einstein equations. We show that the BPS equations, i.e. the conditions of vanishing supersymmetry variations of the space-time fermions, can be directly derived from the worldsheet. To this end we consider a heterotic worldsheet model in the RNS-formulation with (2,0) supersymmetry, which describes a complex torsion target space that supports a holomorphic vector bundle. After a detailed account of its quantization and renormalization, we establish that super Weyl anomaly cancellation implies the heterotic BPS conditions: At the one loop level the geometry is required to be conformally balanced and the gauge background has to satisfy the Hermitean Yang-Mills equations.

 
16:15-16:30 Honecker, MG (Johannes Gutenberg-Universität Mainz)
  Towards the Standard Model on Rigid D-Branes Sem 2
 

D-brane worlds have provided a geometrically intuitive approach for Standard Model (SM) engineering within string theory compactifications. While the types and ranks of gauge groups and the chiral matter content are tackled in a straightforward manner, it remains on the one hand an open question if the SM can be obtained on rigid D-branes - without continuous gauge symmetry breaking along flat directions and with non-trivial D-brane instanton contributions to the effective action - and on the other hand if such models are consistent with low-energy data. The T6/Z(2)xZ(6') orbifold with discrete torsion admits a plethora of left-right symmetric `local models' without exotic matter in the adjoint, symmetric or antisymmetric representation. However, `global' completions usually come at the cost of introducing new exotic states in bifundamental representations. It furthermore turns out that USp(2) and SO(2) in place of U(2) symmetries can at most provide one particle generation. Last but not least, it turns out that for any T6/Z(2)xZ(2M) orbifold with discrete torsion and tilted tori, orientifold invariant stacks of D6-branes carry USp(2N) or SO(2N) gauge groups depending on their relative position to the exotic O6-plane. The new classification reduces the number of K-theory constraints. If time permits, I will briefly comment on the drastic change in the pattern of Yukawa couplings on orbifolds compared to the six-torus using a T6/Z6' example. As a result, quark Yukawas can provide large mixings while lepton Yukawas are flavour diagonal at leading order. Also the rule of `one massive generation only' is circumvented.

 
16:30-16:45 Ruehle, F (Universität Bonn)
  GLSM descriptions of heterotic compactification spaces Sem 1
 

Gauged Linear Sigma Models (GLSMs) provide a framework for studying different phases of compactification spaces for heterotic string theories. Among them are toroidal orbifolds and smooth Calabi-Yau constructions, both of which are very popular among string model builders. Up to now, quite a few MSSM-like string models have been constructed based on these compactification spaces. We describe the construction of toroidal orbifolds and describe how to obtain their smooth Calabi-Yau counterparts in the GLSM framework. The two regimes lie at different regions in Kahler moduli space, which can be accessed by tuning the Fayet-Iliopoulos GLSM parameters. However, upon probing the entire moduli space, also other phases are encountered which do not have a geometric interpretation as straightforward as the previously mentioned ones. Furthermore, there can be flop and flop-like transitions which further subdivide the different phases.

 
16:30-16:45 Witkowski, L (University of Oxford)
  Superpotential de-sequestering as a source of flavour violation Sem 2
 

Non-perturbative effects such as gaugino condensation on a stack of D7-branes are an essential ingredient in several celebrated moduli-stabilisation schemes in type IIB string theory. At the level of the four-dimensional effective theory, the non-perturbative effects induce a non-perturbative superpotential. In particular, new Yukawa interactions can be generated. Type IIB orbifold models contain the essential features to study these non-perturbative corrections to the superpotential in string compactifications. I will describe under which conditions new Yukawa couplings arise in these settings and generalise the results to more realistic string models. Most importantly, I will show that the flavour structure of the induced Yukawa couplings is not aligned with the tree-level flavour structure, thus introducing a new source of flavor violation.

 
16:45-17:00 Parameswaran, S (Leibniz Universität Hannover)
  Coupling Selection Rules in Heterotic Orbifold Compactifications Sem 1
 

Heterotic orbifolds provide a simple, globally consistent framework in which one can obtain the MSSM particle spectrum with no chiral exotics from string theory. In order to understand the dynamical aspects and phenomenology of these compactifications, such as the decoupling of vector-like exotics, moduli stabilization, particle masses and couplings, we must compute the couplings in the corresponding low energy effective field theory.

We study L-point string correlation functions and thus derive string selection rules, which determine the allowed couplings in the superpotential of the low energy effective supergravity theory.

 
16:45-17:00 Marsh, CMD (Cornell University)
  The Coulomb Gas of Random Supergravities Sem 2
 

I will discuss the mass spectrum of four-dimensional {\cal N}=1 supergravity in which the Kähler potential and superpotential are taken to be random functions of N chiral superfields. For both supersymmetric and non-supersymmetric critical points, the ensemble of Hessian matrices can be efficiently studied through the ‘Coulomb gas’ formulation of Random Matrix Theory. At large N, the supersymmetric AdS vacua have a very peculiar spectrum which typically includes many BF-allowed tachyons, and I will briefly discuss the prospects of obtaining metastable de Sitter vacua from an ‘uplift’ of a supersymmetric AdS vacuum. An exponentially small fraction de Sitter critical points with spontaneously broken supersymmetry are metastable vacua, and I will discuss how the Coulomb gas formulation can be used to find the joint probability distribution of the masses, the fraction of critical points which are vacua, and the spectrum of the vacua. I will conclude by b riefly discussing some cosmological consequences of these results.

 
17:00-17:15 Break
17:15-17:30 Hayashi, H (Korea Institute for Advanced Study (KIAS))
  U(n) Spectral Covers from Decomposition Sem 1
 

We construct decomposed spectral covers for bundles on elliptically fibered Calabi-Yau threefolds whose structure groups are S(U(1) x U(4)), S(U(2) x U(3)) and S(U(1) x U(1) x U(3)) in heterotic string compactifications. The decomposition requires not only the tuning of the SU(5) spectral covers but also the tuning of the complex structure moduli of the Calabi-Yau threefolds. This configuration is translated to geometric data on F-theory side. We find that the monodromy locus for two-cycles in K3 fibered Calabi-Yau fourfolds in a stable degeneration limit is globally factorized with squared factors under the decomposition conditions. This signals that the monodromy group is reduced and there is a U(1) symmetry in a low energy effective field theory. To support that, we explicitly check the reduction of a monodromy group in a slice of the moduli space for an E6 gauge theory with (1+2) decomposition. This may provide a systematic way for constructing some F-theory models with U (1) symmetries.

 
17:15-17:30 Guarino, A (Rijksuniversiteit Groningen)
  Exceptional Flux Compactifications Sem 2
 

In the last decade, a framework in which string dualities are implemented at the supergravity level has been developed, i.e., the so-called embedding tensor formalism. However, the connection between this formalism and string theory realisations remains still obscure since most of the supergravities obtained by using the embedding tensor formalism correspond to very exotic (non-)geometries in the string side.

In this talk we consider type II flux backgrounds compatible with the absence of brane sources, and construct their explicit embedding into maximal D=4 supergravity. This enables us to investigate the critical points, mass spectra and gauge groups of such "exceptional" backgrounds in a systematic way. We will chart the landscape of vacua in some specific setups which are relevant from the string theory viewpoint and discuss the issues of stability and supersymmetry at those vacuum solutions. Finally we will point towards some natural extensions of the results.

 
17:30-17:45 Mayrhofer, C (Universität Heidelberg)
  Searching for Phenomenologically Attractive Calabi-Yaus with Kähler Classes Variant under Orientifolding Sem 1
 

We give a detailed account of our search for Calabi-Yau three-folds with two toric del Pezzo divisors of the same kind and an orientifold involution which maps them into each other. We will consider hypersurface Calabi-Yaus in toric four-folds with $h^{1,1}$ up to five and comment on the relevance of these geometries in string phenomenology.

 
17:30-17:45 Borghese, A (Rijksuniversiteit Groningen)
  A geometric bound for F-term inflation Sem 2
 

There has been a lot of efforts during the last decade in order to provide a supergravity realisation of inflation. This is of crucial importance if one look at supergravity as the bridge connecting the effective field theory of inflation and a possible UV complete theory like string theory. Within a supergravity theory the inflationary dynamics is tightly constrained. I will discuss a particular kind of geometric constraints which arise by considering particular directions on the scalar manifold, namely the ones which are singled out by the process of supersymmetry breaking (the so called sGoldstino’s). As an example I will consider the constraint in the case of N=1, F-term inflation.

 
17:45-18:00 Krippendorf, S (Universität Bonn)
  Model building and moduli stabilisation in Calabi-Yau orientifold compactifications with branes at singularities Sem 1
17:45-18:00 Larios Lopez, B (Universidad Nacional Autónoma de México (UNAM))
  On the Beaming of Gluonic Fields at Strong Coupling Sem 2
 

We examine the conditions for beaming of the gluonic field sourced by a heavy quark in strongly-coupled conformal field theories, using the AdS/CFT correspondence. Previous works have found that, contrary to naive expectations, it is possible to set up collimated beams of gluonic radiation despite the strong coupling. We show that, on the gravity side of the correspondence, this follows directly (for arbitrary quark motion, and independently of any approximations) from the fact that the string dual to the quark remains unexpectedly close to the AdS boundary whenever the quark moves ultra-relativistically. We also work out the validity conditions for a related approximation scheme that proposed to explain the beaming effect though the formation of shock waves in the bulk fields emitted by the string. We find that these conditions are fulfilled in the case of ultra-relativistic uniform circular motion that motivated the proposal, but unfortunately do not hold for much more gen eral quark trajectories.

 
19:30-22:00 Conference Dinner at Christ's College
Friday 29 June
09:00-09:35 Ibanez, L (Universidad Autonoma de Madrid and IFT-UAM/CSIC)
  The SUSY breaking scale and F-theory unification Sem 1
09:35-10:10 Schellekens, AN (National Institute for Subatomic Physics (Nikhef))
  Discrete gauge symmetries in discrete orientifolds Sem 1
 

We study the origin of discrete gauge symmetries from open string sector U(1)'s in orientifolds based on rational conformal field theory. By means of an explicit construction, we find an integral basis for the couplings of axions and U(1) factors for all simple current MIPFs and orientifolds of all 168 Gepner models, a total of 32990 distinct cases. We discuss how the presence of discrete symmetries surviving as a subgroup of broken U(1)'s can be derived using this basis. We apply this procedure to models with MSSM chiral spectrum, concretely to all known U(3)xU(2)xU(1)xU(1) and U(3)xSp(2)xU(1)xU(1) configurations with chiral bi-fundamentals, but no chiral tensors, as well as some SU(5) GUT models.

 
10:10-10:45 Faraggi, A (University of Liverpool)
  The Dark OPERA Sem 1
10:45-11:20 Morning Coffee
11:20-11:55 Ovrut, B (University of Pennsylvania)
  Phenomenological Heterotic Theory: Standard Models, the Renormalization Group and All That Sem 1
 

A class of hidden sector polystable vector bundles will be presented that, when used in combination with SU(4) heterotic standard model bundles, lead to completely stable string vacua with exactly the particle spectrum of the MSSM with three right-handed neutrino supermultiplets. Threshold corrections, the effective Lagrangian with soft supersymmetry breaking and its scaling under the renormalization group are discussed. It is shown that gauged B-L symmetry and electroweak symmetry are radiatively broken with a small hierarchy over a wide range of initial parameters. Implications of these SU(4) heterotic standard models for the LHC are explored.

 
11:55-12:30 Lukas, A (University of Oxford)
  Heterotic Line Bundle Models in Four Dimensions Sem 1
 

We introduce heterotic line bundle standard models and, more generally, heterotic split models focusing on their four-dimensional effective supergravity theories. The general structure of these theories and a number of phenomenological issues, including fermion masses, proton decay and moduli stabilization will be discussed.

 
12:30-12:35 Louis, J (Universität Hamburg)
  Announcement of String Pheno 2013 Sem 1
12:35-13:30 Lunch at Wolfson Court
14:00-14:35 Dall’Agata, G (Università degli Studi di Padova)
  New facts on classical and quantum N=8 supergravity Sem 1
 

N=8 supergravity is currently at the center of many investigations because of its possible ultraviolet finiteness. I will present some new results on its spontaneously broken version. I will prove that all models with N=0 Minkowski vacua are finite at 1-loop. I will also discuss a new mechanism to study the classical vacua, show that there are many more deformations than previously expected and that from a stringy perspective broken N=8 supergravity exhibits a moduli space with some intriguing features.

 
14:35-15:10 Garcia-Etxebarria, I (CERN - European Organisation for Nuclear Research)
  New N=1 dualities from contracting orientifolds Sem 1
 

I will describe recent work on a new class of dualities, directly inherited from IIB S-duality, in 4d theories with 4 supercharges.

I will focus on the microscopic description of the duality, when realized in terms of system of branes at singularities in string theory. The theories in question are obtained by considering, in addition to the fractional branes, orientifold planes wrapping vanishing 4-cycles.

I will discuss the system from the point of view of large volume branes, focusing in particular on the relevant issues when continuing orientifolds of quiver gauge theories to large volume. This discussion provides a first principles derivation of the relevant orientifolded quivers. By studying the strongly coupled behavior of the resulting orientifold+brane configuration, I will argue for the existance of a dual, weakly coupled description of the strongly coupled quiver theory at the singularity.

 
15:10-15:45 Closing Comments
15:45-16:20 Afternoon Tea
18:45-19:15 Dinner for Residents at Fitzwilliam & Churchill Colleges

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