![[Logo] Mathematics @ Instituto Superior Técnico](/img/DM_Ersatz.svg "Mathematics @ Instituto Superior Técnico")
17/01/2017, 17:30 — 18:00 — Abreu Faro Amphitheatre
Troels Harmark, Niels Bohr Institute
Interacting Giant Gravitons from Spin Matrix theory
The overall theme of this talk is whether one can find a unifying framework that can connect the gauge and string theory sides of the AdS/CFT correspondence, thus enabling one to quantitatively connect the two sides. This would enable one to study quantitatively how space, time and gravity emerge from a quantum theory. In the planar regime, the integrable spin chain provides such a unifying framework but it cannot be used beyond planar gauge theory and tree-level string theory. Our proposal is that Spin Matrix theory provides a unifying framework near certain unitarity bounds, enabling one to access finite-$N$ effects. We give evidence for this by matching non-supersymmetric dynamics of D-branes on $AdS_5 \times S^5$ to a finite-$N$ regime in $N=4$ SYM near a unitarity bound. In particular, we find an effective matrix model that describes the dynamics of weakly interacting giant gravitons wrapped on three-spheres in the AdS part of $AdS_5 \times S^5$ at high energies using the non-abelian DBI action. In parallel we consider the limit of $N=4$ SYM near a certain unitarity bound where it reduces to the quantum mechanical theory called $SU(2)$ Spin Matrix theory. We show that the exact same matrix model that describes the giant gravitons on the string theory side also provides the effective description in the strong coupling and large energy limit of the Spin Matrix theory.
See also
Talk Lisbon Jan 2017_harmark.pdf
17/01/2017, 17:00 — 17:30 — Abreu Faro Amphitheatre
Jesus Anibal Sierra Garcia, University of Santiago de Compostela
Black hole entropy and $T$-duality with $\alpha'$ corrections
It is known from the work of Horowitz and Welch that in supergravity black hole entropy is invariant under the action of $T$-duality. What happens when $\alpha'$ corrections are included? I will present an $\alpha'$ corrected family of actions -including Type II, bosonic and heterotic strings- that enjoy $T$-duality symmetry. After that, I will show the form of the entropy and its behaviour under the corrected T-duality.
See also
Sierra-Garcia Iberian Strings 17.pdf
17/01/2017, 16:30 — 17:00 — Abreu Faro Amphitheatre
Pedro F Ramírez, Auónoma University of Madrid
Non-Abelian microstates geometries
I will describe the smooth microstate geometries with non-Abelian fields found in 1608.01330. These consist in general families of regular supersymmetric solutions with non-trivial topology, i.e. bubbles, of $N=1$ $ d=5$ Super-Einstein-Yang-Mills theory of supergravity, having the asymptotic charges of a black hole or black ring but with no horizon. The result provides the first approach to understand the microstate structure of non-Abelian black holes.
See also
PFRamirez.pdf
17/01/2017, 15:30 — 16:00 — Abreu Faro Amphitheatre
Yolanda Lozano, University of Oviedo
Linear quivers and non-Abelian T-duals
We will discuss recent progress in the CFT interpretation of non-Abelian T-duality in AdS string theory backgrounds. We will focus on $AdS_5$ and $AdS_4$ examples for which the dual CFT can be identified as specific linear quivers. This reveals an interesting set-up in which non-Abelian T-duals of $AdS_{p+1}$ backgrounds are related to Dp-D(p+2)-NS5 brane intersections.
See also
Lisbon2017-yolanda.pdf
17/01/2017, 14:30 — 15:30 — Abreu Faro Amphitheatre
Alberto Zaffaroni, University of Milano-Bicocca
Supersymmetric localization and AdS4 black holes
One of the great success of string theory is the microscopical explanation of the entropy of a class of asymptotically flat black holes. Much less is known about asymptotically AdS black holes in four dimensions or higher. In this talk I explain how to derive the entropy of a class of asymptotically AdS supersymmetric black holes in four dimensions using holography. The counting of black hole micro-states is related to a counting of states in the dual three-dimensional gauge theory which can be explicitly performed using localization.
See also
IberianStrings_zaffaroni.pdf
17/01/2017, 12:00 — 12:30 — Abreu Faro Amphitheatre
Adolfo Guarino, Université Libre de Bruxelles
Double Field Theory at $SL(2)$ angles
In this talk I will present an extended field theory that captures the full $SL(2) \times O(6,6+n) $ duality group of $N=4$ supergravity in four dimensions. Making use of the $SL(2) $ structure, I will show how to generate gaugings at $SL(2)$ angles via generalised Scherk-Schwarz ansätze. Such gaugings allow for moduli stabilisation including the $SL(2)$ dilaton.
See also
Lisbon_Guarino.pdf
17/01/2017, 11:30 — 12:00 — Abreu Faro Amphitheatre
André Coimbra, Institut des Hautes Études Scientifiques
Generalised Structures for Supersymmetric Backgrounds
Exceptional generalised geometry provides a language with which one can naturally describe M theory and type II with fluxes. In this talk I will show how G-structures defined on the generalised tangent bundle of the internal compactification space which are torsion-free with respect to the exceptional Dorfman bracket are in one-to-one correspondence with Minkowski backgrounds preserving supersymmetry -- they are the precise analogue of the Calabi-Yau conditions for arbitrary flux compactifications, and their solutions are likewise Ricci-flat in the generalised geometric sense. N=1 AdS flux backgrounds can also be neatly described in this formalism, the torsion-free condition being minimally relaxed to accommodate the cosmological constant, yielding generalised Einstein spaces for the geometry of the internal space.
See also
talk Lisboa_andre_coimbra.pdf
17/01/2017, 11:00 — 11:30 — Abreu Faro Amphitheatre
Yi Pang, Albert Einstein Institute
Evidence for the Holographic dual of $N=3$ Solution in Massive Type IIA
We calculate the Kaluza-Klein spectrum of spin-2 fluctuations around the ${\cal N}=3$ warped $AdS4 \times M6$ solution in massive IIA supergravity. This solution was conjectured to be dual to the $D=3 {\cal N}=3$ superconformal $SU(N)$ Chern-Simons matter theory with level k and 2 adjoint chiral multiplets. The $SO(3)_R×SO(3)_D$ isometry of the ${\cal N}=3$ solution is identified with the $SU(2)_F×SU(2)_R$ global symmetry of the dual ${\cal N}=3$ SCFT. We show that the $SO(3)_R×SO(3)_D$ quantum numbers and the AdS energies carried by the BPS spin-2 modes match precisely with those of the spin-2 gauge invariant operators in the short multiplets of operators in the ${\cal N}=3$ SCFT. We also compute the Euclidean action of the ${\cal N}=3$ solution and the free energy of the ${\cal N}=3$ SCFT on $S^3$, in the limit $N \gg k$. Remarkably, the results show a complete agreement.
See also
Iberian_Pang.pdf
17/01/2017, 10:00 — 10:30 — Abreu Faro Amphitheatre
Roberto Emparan, ICREA & University of Barcelona
Black holes in the $1/D$ expansion
We review black holes in the $1/D$ expansion.
See also
BHLargeD_IbStrings2017.pdf
17/01/2017, 09:00 — 10:00 — Abreu Faro Amphitheatre
Daniel Grumiller, Technical University of Vienna
AdS holography and black holes
I review recent boundary conditions in AdS suitable for observers near a black hole horizon. I focus on 3-dimensional Einstein gravity and discuss consequences of these new boundary conditions, in particular the emergence of soft Heisenberg hair and its role for BTZ black hole microstates. Generalizations to flat space, higher derivatives, higher spins and higher dimension are addressed.
See also
grumiller.pdf
16/01/2017, 17:30 — 18:00 — Abreu Faro Amphitheatre
Eduardo Garcia Valdecasas, Autónoma University of Madrid
Stringy instantons, deformed geometry and axions
Axion models can be described in terms of a 3-form eating a 2-form dual to the axion. I will discuss how stringy axions can give rise to potentials for the axion in this language, where there is naively no candidate 3-form to eat up. The necessary 3-form will arise when taking into account the backreaction of the instanton in the underlying geometry. Novel applications of this mechanism and ongoing research might also be presented. Based on arXiv:1605.08092 and ongoing work.
See also
IberianStrings2017_eduardo_valdecasas.pdf
16/01/2017, 17:00 — 17:30 — Abreu Faro Amphitheatre
Tuna Demircik, Sabanci University of Istanbul
Holographic equilibration in confining gauge theories
We investigate the effect of external magnetic fields on equilibration in the improved holographic QCD theory in the deconfined phase using the AdS/CFT correspondence. In particular we calculate the quasinormal mode spectra in the corresponding black brane solutions and study their dependence on temperature, momentum and magnetic field, both in the scalar and the shear channels. We find complex patterns in the motion of quasinormal modes on the complex plane, including certain cross overs between the lowest lying modes under varying magnetic field, momentum and temperature. We also discover a critical value of the magnetic field Bc above which the hydrodynamic approximation breaks down, as the imaginary part of the first excited quasi-normal mode in the shear channel becomes smaller than that of the hydro mode.
See also
T.Demircik:Lisbon.pdf
16/01/2017, 16:30 — 17:00 — Abreu Faro Amphitheatre
Adi Armoni, Swansea University
Holographic Corrections to the Veneziano Amplitude
We propose a holographic computation of the $2 \to 2$ meson scattering in a curved string background, dual to a QCD-like theory. We recover the Veneziano amplitude and compute a perturbative correction due to the background curvature. The result implies a small deviation from a linear trajectory, which is a requirement of the UV regime of QCD.
See also
Lisbon-Armoni.pdf
16/01/2017, 15:30 — 16:00 — Abreu Faro Amphitheatre
Álvaro Véliz-Osorio, Jagellionian University Krakow
On the Shape of Things: From holography to elastica
We explore the question of which shape a manifold is compelled to take when immersed into another one, provided it must be the extremum of some functional. We consider a family of functionals which depend quadratically on the extrinsic curvatures and on projections of the ambient curvatures. These functionals capture a number of physical setups ranging from holography to the study of membranes and elastica. We present a detailed derivation of the equations of motion, known as the shape equations, placing particular emphasis in the issue of gauge freedom in the choice of normal frame. We apply these equations to the specific case of holographic entanglement entropy for higher-curvature three-dimensional gravity and find new classes of entangling curves. In particular, we discuss the case of New Massive Gravity where we show that non-geodesic entangling curves have always a smaller on-shell value of the entropy functional. Nevertheless, the correct value for the entanglement entropy is provided by geodesics. Then, we discuss the importance of these equations in the context of classical elastica and comment on terms that break gauge invariance.
See also
IBST_alvaro_osorio.pdf
16/01/2017, 14:30 — 15:30 — Abreu Faro Amphitheatre
Julian Sonner, University of Geneva
Black hole collapse in CFT
Holography allows us to formulate questions about quantum gravity in terms of more ordinary quantum field theories without gravity. A natural and long-standing goal has been to understand the physics of black holes using holographic duality. I will report on some recent progress on this question formulating the spherical collapse of an in-falling shell of null matter in three dimensions in terms of a first-principles CFT calculation. I will argue that the apparent loss of information in the CFT can be traced back to late-time non-perturbative effects in an expansion in large central charge.
See also
SonnerBHCollapseLisboa.pdf
16/01/2017, 12:00 — 12:30 — Abreu Faro Amphitheatre
Pietro Longhi, Uppsala University
Probing the geometry of BPS states with spectral networks
New relations between wall crossing invariants, such as the BPS monodromy, and various limits of superconformal indices of 4d N=2 theories have been recently proposed. For theories of class S on their Coulomb branches, spectral networks provide a way to compute BPS monodromies directly, in a neighborhood of the superconformal point. Several new results on BPS monodromies can be obtained in this way, bringing new insights into these correspondences.
See also
Longhi_Lisbon.pdf
16/01/2017, 11:30 — 12:00 — Abreu Faro Amphitheatre
Federico Carta, Autónoma University of Madrid
Hilbert Series and Mixed Branches of $3d$, $N=4$, $T[SU(N)]$ theories
We consider mixed branches of $3d$, $N=4$, $T[SU(N)]$ theories. Motivated by the type IIB brane construction, we propose a restriction rule acting on the Hilbert Series of the full Coulomb branch that will truncate the magnetic charge summation only to the subset of BPS dressed monopole operators that arise in the Coulomb branch part of a given mixed branch. We check this proposal in explicit examples, and we further generalize it to the Higgs branch part of a given mixed branch, by exploiting $3d$ mirror symmetry. As a result, we are able to compute the Hilbert Series of any mixed branch of $T[SU(N)]$.
See also
CartaFederico.pdf
16/01/2017, 11:00 — 11:30 — Abreu Faro Amphitheatre
Michael Abbott, Jagiellonian University Krakow
Lüscher Terms & Limitations of the $AdS_3$ Asymptotic Bethe Ansatz
We recently showed that the Bethe equations for $AdS_3$ integrability describe the spectrum of a much smaller sector than was the case for $AdS_5/CFT_4$. The reason is that wrapping corrections enter much earlier than before, thanks to the presence of massless modes. This explains a mismatch that was seen in one of the classic tests of AdS/CFT integrability, namely the study of circular spinning strings from which Hernandez & Lopez deduced the one-loop dressing phase for AdS5. Several other mismatches may be caused by the same physics.
See also
Abbott - Iberian Strings 2017 - Lisbon-slides-02.pdf
16/01/2017, 10:00 — 10:30 — Abreu Faro Amphitheatre
Miguel Tierz, Faculdade de Ciências of Lisbon University
Quantum phase transition in supersymmetric QED in three dimensions
We present a study of $\mathcal{N}=4$ supersymmetric QED in three dimensions, on a three-sphere, with $2N$ massive hypermultiplets and a Fayet-Iliopoulos parameter. We identify the exact partition function of the theory with a conical (Mehler) function. This implies a number of analytical formulas, including a recurrence relation and a second-order differential equation. In the large $N$ limit, the theory undergoes a second-order phase transition on a critical line in the parameter space. We will discuss the critical behavior and compute the two-point correlation function of a gauge invariant mass operator.
(Joint work with Jorge G. Russo, arXiv:1610.08527)
See also
Talk-IbStrings_Tierz.pdf
16/01/2017, 09:00 — 10:00 — Abreu Faro Amphitheatre
Inês Aniceto, Jagiellonian University Krakow
Asymptotics and Resurgence in String and Gauge Theories
The perturbative expansions of many physical quantities are divergent, and defined only as asymptotic series. It is well known that this divergence reflects the existence of nonperturbative contributions, such as instanton effects, which are not captured by a perturbative analysis. This connection between perturbative and nonperturbative sectors of a given physical observable can be systematically studied using the theory of resurgence, allowing us to construct a full non-perturbative solution from perturbative asymptotic data. In this lecture I will start by reviewing the essential role of resurgence theory in the description of the analytic solution behind an asymptotic series, and its relation to the so-called Stokes phenomena, phase transitions and ambiguity cancelations. I will then present the most recent applications of resurgence in the context of string and gauge theories.