Speakers

Alex Arvanitakis (Imperial Coll., London):Generalised geometry, branes and L-infinity algebras/oids.

Abstract: 11-dimensional supergravity acquires a global symmetry when compactified (the U-duality group) whose 11-dimensional origin is yet unknown. Generalised geometry attempts to explain the U-duality group by reformulating supergravity in terms of U-duality multiplets. We describe our study of the mathematical structure of generalised geometry, and the unexpected resulting connection to the physics of strings and branes and topological field theories of the AKSZ type.

Anastasia Doikou (Heriot-Watt University): Stochastics & Discrete Quantum Systems.

Abstract: We explore the connections between the theories of stochastic analysis and discrete quantum mechanical systems. Naturally, these connections include the Feynman-Kac formula, and the Cameron-Martin-Girsanov theorem. We employ the notion of the quantum canonical transformation to simplify the form of the genric multi-particle quantum Hamiltonian. Precise computation of the path integral leads to a universal expression for the associated measure regardless of the form of the diffusion coefficient and the drift. This computation also reveals that the drift plays the role of a super potential in the usual super-symmetric quantum mechanics sense. Basic examples of quantum integrable systems such as the quantum discrete non-linear hierarchy and the XXZ spin chain are presented providing specific connections between quantum systems and stochastic differential equations (SDEs). The continuum limits of the SDEsfor the first two members of the NLS hierarchy turn out to be the stochastic transport and the stochastic heat equations respectively. (Work in collaboration with S.J.A. Malham & A. Wiese).

Fotis Farakos (KU Leuven): FI terms in supergravity without gauged R-symmetry.

Abstract: We present a new embedding of the Fayet-Iliopoulos D-term in supergravity that does not require the gauging of the R-symmetry and we study its relation to anti D3-branes.

Andreas Goudelis (LPTHE, Paris) : Dark matter freeze-in: theory and phenomenology.

Abstract: The existence of dark matter is by now well-established, based essentially on evidence stemming from gravitational observations. Determining its potential non-gravitational properties and, eventually, its nature, is one of the most important questions in contemporary high-energy physics and cosmology. In this talk I will discuss some ideas about its origin, i.e. the question of why there is as much dark matter in the Universe as we observe. I will focus on the so-called freeze-in mechanism, and discuss through which types of observations we could constrain and, eventually, discover frozen-in dark matter.

Goergios Linardopoulos (National and Kapodistrian University of Athens & NCSR Demokritos) : Solving Holographic Defects.

Abstract: Defect conformal field theories (dCFTs) have been attracting increased attention recently, mainly because they enable us to bridge the gap between idealistic, highly symmetric models of our world (such as the particle/string duality) and real-world systems. This talk will be about the AdS/defect CFT correspondence, an exciting new proposal that joins the forces of holography, integrability and the conformal bootstrap program in a framework that is appropriate for the study of defects in real-world systems. After introducing defect CFTs and some of their holographic realizations, we will present some recent results for the one-point functions of the dCFTs that are dual to the D3-D5 and D3-D7 systems of intersecting branes.

Chrysoula Markou (Max-Planck-Institut Munich) : The linear dilaton: from the clockwork mechanism to its supergravity embedding.

Abstract: The recently proposed clockwork mechanism is a means of generating an exponential scale separation without assuming very small (or very large) parameters at a fundamental level. In its discrete version, it enjoys a low-energy effective field theory realization in four dimensions in terms of a type of quiver theory on a finite one-dimensional lattice, with a key ingredient being the asymmetric distribution of a type of charge along the sites of the lattice. In its continuum version, the discrete dimension of the lattice gives its place to a compact extra dimension, which yields a perhaps surprising observation: the resulting five-dimensional metric and Kaluza-Klein graviton spectrum are precisely those arising from the toy model for the holographic dual of six-dimensional little string theory. The latter belongs to a class of theories obtained from string theory in the limit of vanishing string coupling that are notoriously hard to study, interestingly so in contrast to their duals. The toy model captures the important features of the dual, that is, it contains a potential that generates a linear dilaton background. Moreover, it turns out that a particular gauging of N=2 supergravity in five dimensions generates a potential whose parameters can be tuned to those of the dilaton potential of the toy model. The linear dilaton background then breaks supersymmetry partially, with N=1 remaining intact in four dimensions. Time permitting, a comparison with Randall-Sundrum models and large extra dimensions will be given.

Olga Papadoulaki (ICTP) : Euclidean Wormholes and Holography.

Abstract: I will give a short introduction on holography and wormholes as well as why it is interesting to study such solutions. Then I will present the specific solutions that we study, how to compute scalar and Wilson loop correlators on such geometrical backgrounds. I will end with the presentation of a proposed holographic dual.

Georgios Papathanasiou (DESY): Scattering amplitudes and cluster algebras.

Abstract: Scattering amplitudes form a bridge connecting theoretical particle physics with the real world of collider experiments, yet their computation by means of Feynman diagrams quickly becomes prohibitive. Focusing on the simplest interacting gauge theory, known in maximally supersymmetric Yang–Mills, in this talk I present recent progress in bypassing these limitations and directly constructing amplitudes, by exploiting their expected analytic structure. Remarkably, this analytic structure is governed by a mathematical object known as a cluster algebra, whose highly nontrivial implications I describe.

Konstantinos Siampos (CERN) : Holographic reconstruction of Einstein spacetimes.

Abstract: Using the fluid/gravity correspondence, we present an explicit approach that allows us to reconstruct a class of exact four-dimensional Einstein space-times. If the boundary metric supports a traceless, symmetric and conserved energy–momentum tensor, and if the fluid velocity is shearless, then the bulk metric is exactly resummed. We illustrate the method in two simple examples, the Schwarzschild and Taub-NUT space-times.

Spyros Sotiriadis (University of Ljubljana): Dynamics and relaxation in quantum out-of-equilibrium systems.

Abstract: The derivation of statistical mechanics laws, that describe the macroscopic behaviour of physical systems, from the more fundamental laws of quantum physics, that describe their microscopic behaviour, remains one of the main open questions in theoretical physics. Research in the field of out-of-equilibrium quantum physics has recently unveiled extraordinary non-ergodic dynamics and relaxation to non-thermal steady states that is attributed to integrability. Focusing on the dynamics of Quantum Field Theories after an abrupt parameter change, known as quantum quench, I will present an analytical method to demonstrate equilibration to such non-thermal statistical ensembles in the simplest possible scenario. I will then present a Conformal Field Theory based numerical method to study the more complex dynamics of a prototypical example of Integrable Quantum Field Theory, the sine-Gordon model.

Daniel Thompson (Swansea University): Generalised String Dualities and Integrability.

Abstract: A remarkable property of the string theory approach to quantum gravity is duality: seemingly very different space time geometries can be equivalent from the point of view of strings. In this talk I shall review advances in generalised notions of T-duality. First I shall describe how non-abelian T-duality can be employed together with holography to define new quantum field theories. I will show that there is a rich interplay of duality and integrability; a rich set of symmetries that render apparently complex dynamics solvable. Finally I will mention some recent works that have extended these duality transformations to give rise to classes of integrable string theory models.

Konstantinos Zoubos (University of Pretoria): Marginal deformations and quasi-Hopf algebras.

Abstract: We study the global symmetries of the N=1 supersymmetric exactly marginal deformations of the N=4 Super-Yang-Mills theory in four dimensions. It turns out that these symmetries can be simply related to those of the original N=4 theory through a procedure known as a Drinfeld twist, which we will introduce. The outcome of the twist is not a Lie algebra, but a more general structure known as a quasi-Hopf algebra. A suitable star product allows us to deform any expressions in the original theory to those in the twisted theories. We expect our results to be relevant to studies of integrability in these theories, as well as to provide useful input for supergravity solution-generating techniques.