##### Workshop

#### Holographic Methods for Strongly Coupled Systems

**Mar, 09 2015 - Apr, 30 2015**

**Organizers**

Francesco Bigazzi, (INFN, Pisa, Italy), Aldo L. Cotrone (Firenze University, Italy), Nick Evans (Southampton University, U.K.), Elias Kiritsis (Crete University, Greece and APC, France), Hong Liu (Massachusetts Institute of Technology, U.S.A.),

Carlos Nunez (Swansea University, U.K.), Kostas Skenderis (Southampton University, U.K.)

**Contact**

aldo.cotrone@fi.infn.it

fbigazzi@pi.infn.it

**Related events**

Gauge/Gravity Duality 2015 (Conference) - Apr, 13 2015

**Abstract**

The methods of holography - the mapping between quantum field theories and higher dimensional theories of gravity - have reached a mature development stage, where they can be used as tools to understand strongly interacting systems arising in a variety of important physical problems. Formal developments (for instance in the light of integrability) beautifully complement applications towards experimentally accessible systems, at low energy (condensed matter) as well as at high-energy (QCD, electroweak symmetry breaking, dynamical supersymmetry breaking). In view of relevant data coming from LHC experiments as well as of the discovery of novel materials which evade standard descriptions based on weakly interacting quasi-particles (e.g. strange metals, high-Tc superconductors, topological insulators) together with the development of advanced techniques (from nanotechnologies to cold atoms simulations) which have opened new windows to the study of non-equilibrium physics, it is crucial for the international community of theoretical physicists to identify priorities and coordinate efforts to better understand these phenomena.

Moreover, recent developments have highlighted the power of holography to analyze entanglement issues, which have attracted much attention for their relevance in condensed matter systems, information theory and gravity.

With this aim in mind, the Workshop will be mainly focused on applications of the holographic correspondence to particle, nuclear, condensed matter and gravitational physics. The goal would be to coordinate the research activity on the field, to identify objectives and priorities and to encourage and facilitate international collaborations.

A conference will be organized within the Workshop.

- Dates of the Conference:

April 13, 2015 - April 17, 2015

**Topics**

- Holographic QCD

- Holography and condensed matter

- Holography and out of equilibrium physics

- Holography, entanglement and information

- Holography and cosmology

- Advances in supersymmetric gauge theories and integrability

**Talks**

Mar, 09 2015 - 15:00 | Arkady Tseytlin | Vectorial AdS/CFT and quantum higher spins | Seminar | We will review recent work on computing one-loop corrections |
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Mar, 10 2015 - 15:00 | Joan Camps | Refining Generalized Entropy | Seminar | The Ryu-Takayanagi proposal in AdS/CFT hints to a deep role of |
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Mar, 11 2015 - 11:30 | Pasquale Calabrese | Entanglement negativity and quantum field theories | Seminar | Slides | |||

Mar, 12 2015 - 11:30 | Pawel Caputa | Quantum entanglement and local excitations | Seminar | Excitations in the form of local operators can be characterised from the perspective of quantum entanglement. I will describe the framework and results that illustrate this. |
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Mar, 13 2015 - 11:30 | Sumit Das | Scaling in quantum quench and holography | Seminar | In recent years the problem of quantum quench in the vicinity of |
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Mar, 16 2015 - 15:00 | Tassos Petkou | Aspects of Higher-Spin/Vector Models Holography | Seminar | Slides | |||

Mar, 17 2015 - 11:30 | Romuald Janik | OPE coefficients, string field theory vertex and integrability | Seminar | One of the key open problems in solving N=4 Super-Yang-Mills theory |
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Mar, 18 2015 - 11:30 | Irina Arefeva | QGP time formation in holographic shock waves model of heavy ion collisions | Seminar | We estimate the thermalization time in two colliding shock waves |
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Mar, 19 2015 - 11:30 | Antonio Garcia Garcia | Defect formation beyond Kibble-Zurek mechanism and holography | Seminar | We study the dynamic after a smooth quench across a continuous transition from the disordered phase to the ordered phase. Based on scaling ideas, linear response and the |
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Mar, 20 2015 - 11:30 | Tatsuo Azeyanagi | Anomalies, Chern-Simons Terms and Black Hole Entropy | Seminar | Recently, the hydrodynamic limit of the systems with quantum anomalies has been actively investigated, together with its holographic description by gravitational theories with Chern-Simons terms. In this presentation, I will start with a brief review on some recent results related to the anomalies in the hydrodynamic limit, and then reproduce these results systematically by using the dual gravitational description. In particular, I will explain the crucial roles of the anomaly polynomials there. I will also discuss the implication of our analysis to microscopic entropy counting for black holes in higher dimensions. |
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Mar, 23 2015 - 15:00 | Maria Paola Lombardo | Phases of Strong interactions: lattice results | Seminar | QCD with Nf fundamental fermions has a rich phase structure which has been studied with analytic and numerical studies. I present recent lattice studies for Nf ranging from zero to twelve, at zero and nonzero temperature. The results, which include the critical number of flavor, the approach to the conformal window and the nature of the thermal transition, are amenable to interesting comparisons with holographic analysis. |
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Mar, 24 2015 - 11:30 | Irene Amado | Black brane steady states | Seminar | I will present the evolution of black brane solutions in the presence of a fixed spatial gradient of temperature until the formation of a steady state. The energy density and energy flux of the resulting steady state in the boundary theory are compared with the conjectured behaviour of steady states in conformal field theories. Very good agreement is found. |
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Mar, 25 2015 - 11:30 | Elena Caceres | Holographic entanglement entropy in Gauss-Bonnet theories: time and shadows | Seminar | Slides | |||

Mar, 26 2015 - 11:30 | Erik Tonni | Aspects of entanglement of/between disjoint regions in CFT and holography | Seminar | Mutual information and logarithmic negativity are important quantities to understand entanglement in pure and mixed states. In quantum field theories they are computed by employing a method based on the replica limit. We present a numerical method to compute the holographic mutual information in AdS4 for generic shapes and another numerical method to address the replica limit that turns out to be useful whenever the replica limit is not known analytically, like for the entanglement entropy of disjoint intervals in 2D CFTs. We also discuss the logarithmic negativity at finite temperature in 2D CFTs. |
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Mar, 27 2015 - 11:30 | Cynthia Keeler | A Caveat for Applied Holography | Seminar | After a brief review of holographic techniques derived from the |
Slides | Bonus material | |

Mar, 30 2015 - 15:00 | Nick Evans | Vacuum Alignment in Holographic Graphene | Seminar | Somewhat inspired by graphene in which 2+1d Dirac fermions couple to strongly coupled 3+1d QED I investigate the D3/probe D5 holographic system. A magnetic field induces fermion condensation on the probe and there is a complex temperature vs chemical potential phase structure including a BKT transition at zero T with mu. The transition can be phenomenologically distorted into various non-mean field transitions. When two layers are introduced an additional dynamical mass generation can occur with condensation of fermions between different layers. With a B field a dynamical vacuum alignment problem results and we investigate the phase structure. In the presence of chemical potential as well it is possible to realize a phase with both condensation mechanisms present. Finally I consider how to describe the holographic graphene between two mirrors that compactify the gauge theory mimicing ideas for how real graphene could be made more strongly coupled in the lab. Condensation with the mirror graphene sheet is possible and a complex phase struture again results. |
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Apr, 07 2015 - 15:00 | Kostas Skenderis | Renormalised 3-point functions in CFT | Seminar | I will present a first principles analysis of the constraints of conformal invariance in momentum space. In particular, I will derive the form of the 3-point functions of scalar operators, conserved currents and the energy momentum tensor in momentum space and discuss renormalization and associated anomalies. |
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Apr, 08 2015 - 11:30 | Riccardo Argurio | Holography and the dynamical breaking of supersymmetry | Seminar | Slides | |||

Mar, 31 2015 - 11:30 | Amihay Hanany | Coulomb Branch Hilbert Series and the Moduli Space of Instantons | Seminar | The moduli space of k G instantons on C^2, where G is a classical gauge group, has a well known HyperKahler quotient formulation known as the ADHM construction. The extension to exceptional groups is an open problem. In string theory this is realized using a system of branes, and the moduli space of instantons is identified with the Higgs branch of a particular supersymmetric gauge theory with 8 supercharges. A less known, and less studied aspect of moduli spaces of instantons is that they can be realized as the Coulomb branch of a supersymmetric gauge theory in 2+1 dimensions with 8 supercharges. |
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Apr, 01 2015 - 11:30 | Dario Martelli | Exact results in supersymmetric field theories and holography | Seminar | I will discuss some exact results in four dimensional supersymmetric field theories. After reviewing supersymmetric field theories on curved manifolds and the technique of localization, I will focus on the index and the Casimir energy in curved space. I will conclude discussing the holographic counterpart of these results and open problems. The talk will be based on results obtained during the last year as well as a paper recently submitted to the arxive. |
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Apr, 03 2015 - 11:30 | Andrei Starinets | Universal identity in second order fluid dynamics | Seminar | In 2008, Haack and Yarom demonstrated that there exists a relation |
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Apr, 02 2015 - 11:30 | Stefano Cremonesi | 2d N=(2,2) supersymmetry on curved space and localization on spheres | Seminar | In this talk I will present exact results for two-dimensional N=(2,2) supersymmetric gauge theories, which can be used to study string compactifications on Calabi-Yau manifolds exactly in alpha". I will review the basic properties of these theories, explain how they can be formulated on curved space backgrounds, and finally present localisation formulas for their path integrals on two different supersymmetric backgrounds on the 2-sphere. |
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Apr, 09 2015 - 11:30 | Michela Petrini | Marginal deformations of N=1 SCFT from geometry | Seminar | ||||

Apr, 10 2015 - 11:30 | Alessandro Tomasiello | New 6d superconformal models from string theory, and their compactifications | Seminar | I will describe three infinite classes of analytic AdS_d solutions in massive IIA string theory, for d=7,5,4. The AdS7 solutions are conjectured to be dual to a family of (1,0)-supersymmetric CFT6’s living on an NS5-D6-D8 system. The AdS5 and AdS4 classes are dual to twisted compactifications of these (1,0) theories; their metrics and fluxes can be obtained by a simple universal map from the AdS7 ones. I will then mention an F-theoretical extension of the 6d CFT’s, which as a byproduct suggests the existence of “fractional M5-branes”. |
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Apr, 20 2015 - 15:00 | Konstantin Zarembo | Phase transitions, exact results and holography in N=2* theory | Seminar | ||||

Apr, 21 2015 - 11:30 | Gregory Korchemsky | Four-point correlation function of stress-energy tensors in AdS/CFT | Seminar | ||||

Apr, 22 2015 - 11:30 | Hong Liu | An upper bound on ballistic propagation of entanglement | Seminar | ||||

Apr, 23 2015 - 11:30 | Roberto Emparan | Black holes in the 1/D expansion | Seminar | When the number of dimensions is very large, the gravitational field of a black hole is strongly localized near the horizon. Therefore in this limit the black hole can be effectively identified with a surface in an empty background geometry. The Einstein equations determines the effective equations that this "black hole surface" must satisfy. When the black hole is static, they are the same as the equations for soap films. I will describe how this new effective theory of black holes can be used to solve for non-trivial black hole geometries in a very efficient way. |
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Apr, 24 2015 - 11:30 | Giuseppe Dâ€™Appollonio | String-brane collisions: tidal excitations and time delays | Seminar | We review some recent work on the high-energy scattering of a closed string on a stack of D-branes. We first discuss the (tidal) excitation of the massive string modes and show that the inelastic transition amplitudes are all given by the matrix elements of a particularly simple operator, the eikonal operator. We then analyze the time delay of the string-brane scattering process and show that the potential causality violations due to higher-derivative corrections to the Einstein-Hilbert action recently pointed out by Camanho et al. do not occur in string theory as a consequence of its Regge behaviour. |
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Apr, 20 2015 - 11:30 | Hans Dosch | Superconformal Quantum Mechanics and Light Front Holographic QCD | Seminar | An effective QCD light-front Hamiltonian for mesons and baryons is constructed from generalized supercharges of a superconformal algebra. The introduction of a scale inside the algebra fixes completely the light-front potential from a common general principle. The method can be applied in two formally very similar, but physically distinct ways. On one hand the supercharges can transform the different chiral components of the baryons into each other, on the other hand the positive chiral component of a baryon can be related with a meson wave function. With this construction the striking similarities between meson and baryon spectroscopy are explained. In particular the pion/b1 trajectory is identified as the superpartner of the nucleon trajectory. The lowest-lying state, however, on this trajectory, the pi-meson, is massless in the chiral limit and has no supersymmetric partner. Some preliminary results for the case of explicit breaking of conformal symmetry by (large) quark masses are presented. |
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Apr, 27 2015 - 15:00 | Giuseppe Policastro | Boost-invariant flow on non-conformal plasmas | Seminar | I will report on a generalization of the Bjorken flow, a solution of hydrodynamics under the assumption of boost-invariance, whose dual gravity solution was found by Janik and Peschanski, to a class of non-conformal theories described by an Einstein+dilaton model in the bulk. The results could be relevant to the thermalization of the quark-gluon plasma of QCD. |
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Apr, 28 2015 - 11:30 | Carlos Hoyos | Ward identities and transport in 2+1 dimensions | Seminar | The Hall viscosity of chiral superfluids is determined by the angular momentum density. One can understand and generalize this relation using Ward identities of the energy-momentum tensor. Furthermore, the same identities connect viscosities and conductivities. A preliminary analysis in AdS/CFT reveals that the identities seem to be non-trivial in the sense that they cannot be derived simply from the asymptotic expansion of the solutions. |
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Apr, 29 2015 - 11:30 | Javier Tarrio | Instabilities of finite density SYM theories from holography | Seminar | Gauge field configurations carrying instanton number on the worldvolume of probe branes on the geometry of a stack of Dp-branes are dual to scalar operators with non-trivial vacuum expectation values in supersymmetric Yang-Mills theories. This configurations do not change the free energy of the theory and therefore describe a moduli space: the Higgs branch. In the presence of a large charge density the background geometry changes, and the moduli space is lifted. We will investigate whether in the probe limit the configurations with non-trivial VEVs of the scalar operators are energetically preferred and signal an instability of the setup to a phase with condensation. |
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Apr, 30 2015 - 11:30 | Francesco Nitti | Holographic RG flows and quantum effective actions (with applications to QCD) | Seminar |