Triangle Seminars
July 2015
Wed
29 Jul 2015
Connections on Courant Algebroids
Branislav Jurco
(Charles University/MPIM)
Abstract:
We introduce connection, torsion and curvature for Courant algebroids. We discuss in detail torsionless connections compatible with a generalized metric and the related Einstein-Hilbert actions.
We introduce connection, torsion and curvature for Courant algebroids. We discuss in detail torsionless connections compatible with a generalized metric and the related Einstein-Hilbert actions.
Posted by: IC
Tue
28 Jul 2015
TBA
📍 London
SEMPS Conference
(King's College)
Abstract:
Program at: http://www.mth.kcl.ac.uk/~k1469797/ECRSEMPS15/
Program at: http://www.mth.kcl.ac.uk/~k1469797/ECRSEMPS15/
Posted by: KCL
Wed
1 Jul 2015
Localization in Quiver Quantum Mechanics
Kazutoshi Ohta
(Meiji Gakuin University)
Abstract:
We derive the localization formula for N=4 supersymmetric quiver quantum mechanics in the Higgs and Coulomb branch. The partition function (index) is exactly evaluated and it is shown that the path integral is localized at fixed points, which are given by solutions to
the BRST equations combined with D-term and F-term conditions. We give various examples of the quiver theory and classifications of their fixed points. The indexes completely agree with the mathematical wall crossing formulae for the quiver moduli spaces. We also discuss a gravitational picture of the localization in the Coulomb branch.
We derive the localization formula for N=4 supersymmetric quiver quantum mechanics in the Higgs and Coulomb branch. The partition function (index) is exactly evaluated and it is shown that the path integral is localized at fixed points, which are given by solutions to
the BRST equations combined with D-term and F-term conditions. We give various examples of the quiver theory and classifications of their fixed points. The indexes completely agree with the mathematical wall crossing formulae for the quiver moduli spaces. We also discuss a gravitational picture of the localization in the Coulomb branch.
Posted by: IC
June 2015
Tue
30 Jun 2015
Localization in Quiver Quantum Mechanics
Kazutoshi Ohta
(Meiji Gakuin University)
Fri
26 Jun 2015
Strings of 6d SCFTs
📍 London
Babak Haghighat
(Harvard)
Abstract:
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
Posted by: KCL
Thu
25 Jun 2015
Strings of 6d SCFTs
Babak Haghighat
(Harvard)
Abstract:
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
Posted by: QMW
Wed
24 Jun 2015
Defects and quantum Seiberg-Witten geometry
Peter Koroteev
(PI)
Tue
23 Jun 2015
Strings of 6d SCFTs
Babak Haghighat
(Harvard)
Abstract:
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.
Posted by: IC
Mon
8 Jun 2015
Warped Conformal Field Theory as Lower Spin Gravity
Diego Hofman
(UVA)
Abstract:
Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non AdS space-times, including the near horizon geometry of generic extremal black holes. I’ll explain that WCFTs posses a type of boost symmetry. Using this insight, I’ll discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories will be discussed as well as examples of WCFTs. Lastly I’ll present a systematic description of the holographic duals of WCFTs. I’ll argue that the minimal setup is not Einstein gravity but an SL(2,R) x U(1) Chern-Simons Theory, which we call Lower Spin Gravity.
Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non AdS space-times, including the near horizon geometry of generic extremal black holes. I’ll explain that WCFTs posses a type of boost symmetry. Using this insight, I’ll discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories will be discussed as well as examples of WCFTs. Lastly I’ll present a systematic description of the holographic duals of WCFTs. I’ll argue that the minimal setup is not Einstein gravity but an SL(2,R) x U(1) Chern-Simons Theory, which we call Lower Spin Gravity.
Posted by: IC
Wed
3 Jun 2015
Reconstructing holography as a RG flow
Ayan Mukhopadhyay
(CCTP and CCQCN, University of Crete)
Abstract:
I will argue that the holographic correspondence can be reconstructed in the large N and strongly interacting limit as a specific generalisation of Wilsonian RG flow, which can be defined via three simple principles. I will also give an explicit example for such a reconstruction, where dual non-linear classical gravity equations in the long wavelength approximation will emerge from specific kinds of coarse graining of hydrodynamics in the field theory.
I will argue that the holographic correspondence can be reconstructed in the large N and strongly interacting limit as a specific generalisation of Wilsonian RG flow, which can be defined via three simple principles. I will also give an explicit example for such a reconstruction, where dual non-linear classical gravity equations in the long wavelength approximation will emerge from specific kinds of coarse graining of hydrodynamics in the field theory.
Posted by: IC
May 2015
Wed
27 May 2015
Entanglement Entropy in Massive Quantum Field Theories
Olalla Castro Alvaredo
(City U.)
Abstract:
In this talk I will review some of the main results of my research in this area, which stated in 2007 in collaboration with John L. Cardy and Benjamin Doyon. I will emphasise how a special type of field we have named branch point twist field has become an essential tool for performing computations of the entanglement entropy in non-critical systems. I will show how the relationship between correlators of twist fields and entanglement entropy allows us to recover well-known results for critical systems but also to predict new results for theories with a finite correlation length. Time permitting, I will mention some more recent results extending our understanding to non-unitary critical and non-critical systems.
In this talk I will review some of the main results of my research in this area, which stated in 2007 in collaboration with John L. Cardy and Benjamin Doyon. I will emphasise how a special type of field we have named branch point twist field has become an essential tool for performing computations of the entanglement entropy in non-critical systems. I will show how the relationship between correlators of twist fields and entanglement entropy allows us to recover well-known results for critical systems but also to predict new results for theories with a finite correlation length. Time permitting, I will mention some more recent results extending our understanding to non-unitary critical and non-critical systems.
Posted by: IC
Thu
21 May 2015
Multijet Predictions for the LHC
Harald Ita
(Freiburg U.)
Abstract:
In this talk we present recent advances on NLO QCD corrections, performed with BlackHat+SHERPA, to processes with many jets in the final state relevant for the LHC. Furthermore, we will discuss the importance of scattering amplitudes for developing strategies to measure the "out of reach" parameters of the Higgs boson.
In this talk we present recent advances on NLO QCD corrections, performed with BlackHat+SHERPA, to processes with many jets in the final state relevant for the LHC. Furthermore, we will discuss the importance of scattering amplitudes for developing strategies to measure the "out of reach" parameters of the Higgs boson.
Posted by: QMW
Tue
19 May 2015
Extremal chiral ring states in AdS/CFT are described by free fermions
David Berenstein
(UCSB)
Abstract:
Half BPS states (operators) in N=4 SYM are famously described by free fermions both at weak and strong coupling. I describe a set of conjectures for a preferred class of states in more general conformal field theories that can be tested in supergravity for when such a free fermion description might arise and some motivation for it applying generally. The states in question belong to the chiral ring of a supersymmetric conformal field theory that extremize an additional U(1) charge for fixed dimension and can be reduced to multi-traces of a composite matrix field, which is equivalent to using Young tableaux (Schur polynomials) as a basis. The main conjecture asserts that
if the Young tableaux are orthogonal, then the set of extremal three point functions of traces to order 1/N are determined up to a single constant. The conjecture is extended further by providing an exact norm for the Schur basis and this norm arises from a set of free fermions for a generalized oscillator algebra.
Half BPS states (operators) in N=4 SYM are famously described by free fermions both at weak and strong coupling. I describe a set of conjectures for a preferred class of states in more general conformal field theories that can be tested in supergravity for when such a free fermion description might arise and some motivation for it applying generally. The states in question belong to the chiral ring of a supersymmetric conformal field theory that extremize an additional U(1) charge for fixed dimension and can be reduced to multi-traces of a composite matrix field, which is equivalent to using Young tableaux (Schur polynomials) as a basis. The main conjecture asserts that
if the Young tableaux are orthogonal, then the set of extremal three point functions of traces to order 1/N are determined up to a single constant. The conjecture is extended further by providing an exact norm for the Schur basis and this norm arises from a set of free fermions for a generalized oscillator algebra.
Posted by: IC
Wed
13 May 2015
Resolved Warped Deformed Conifolds and Black M3-Branes in the Large-N MQGP Limit
📍 London
Aalok Misra
(Indian Institute of Technology)
Abstract:
We will discuss the construction of type IIA mirror a la Strominger Yau Zaslow prescription and its M-theory uplift in the delocalized limit {resulting in black M3-branes=asymptotically black M5-branes wrapping large integer sum of two-spheres in AdS_5xM_6} of type IIB backgrounds involving non-Kaehler resolved warped deformed conifolds in the presence of [fractional]D3 and wrapped D7-branes relevant to thermal QCD with fundamental quarks. We will show that the local T^3 relevant to SYZ mirror construction obeys the same constraint as the maximal T^2-invariant special Lagrangian three-cycle of deformed conifolds. We also discuss evaluation of the SU(3) structure torsion classes of the type IIB background and show its (approximate) Kaehlerity. We will also discuss thermodynamical/hydrodynamical properties as well as evaluation of a variety of transport coefficients {from correlation functions of gauge and metric fluctuations}, speed of sound and QCD deconfinement temperature consistent with lattice data.
We will discuss the construction of type IIA mirror a la Strominger Yau Zaslow prescription and its M-theory uplift in the delocalized limit {resulting in black M3-branes=asymptotically black M5-branes wrapping large integer sum of two-spheres in AdS_5xM_6} of type IIB backgrounds involving non-Kaehler resolved warped deformed conifolds in the presence of [fractional]D3 and wrapped D7-branes relevant to thermal QCD with fundamental quarks. We will show that the local T^3 relevant to SYZ mirror construction obeys the same constraint as the maximal T^2-invariant special Lagrangian three-cycle of deformed conifolds. We also discuss evaluation of the SU(3) structure torsion classes of the type IIB background and show its (approximate) Kaehlerity. We will also discuss thermodynamical/hydrodynamical properties as well as evaluation of a variety of transport coefficients {from correlation functions of gauge and metric fluctuations}, speed of sound and QCD deconfinement temperature consistent with lattice data.
Posted by: KCL
Tue
12 May 2015
Quantum hydrodynamic integrable systems and gauge theories
📍 London
Antonio Sciarappa
(SISSA (Trieste))
Abstract:
Hydrodynamic integrable systems are characterized by an infinite number of conserved quantities and can be described in terms of integrable partial differential equations. I will focus on the periodic Intermediate Long Wave (ILW) system, both at the classical and quantum level. The quantum system has not been solved yet, if not in a particular limit (the Benjamin-Ono limit) which is related to the AGT correspondence.
In this talk I will show how a particular two dimensional N=(2,2) gauge theory on S^2 can be used to determine the spectrum of the quantum ILW system via Bethe Ansatz equations, as well as the norm of the eigenstates. In addition the partition function of this theory computes genus zero Gromov-Witten invariants for the ADHM instanton moduli space, thus relating quantum cohomology to quantum hydrodynamics.
Hydrodynamic integrable systems are characterized by an infinite number of conserved quantities and can be described in terms of integrable partial differential equations. I will focus on the periodic Intermediate Long Wave (ILW) system, both at the classical and quantum level. The quantum system has not been solved yet, if not in a particular limit (the Benjamin-Ono limit) which is related to the AGT correspondence.
In this talk I will show how a particular two dimensional N=(2,2) gauge theory on S^2 can be used to determine the spectrum of the quantum ILW system via Bethe Ansatz equations, as well as the norm of the eigenstates. In addition the partition function of this theory computes genus zero Gromov-Witten invariants for the ADHM instanton moduli space, thus relating quantum cohomology to quantum hydrodynamics.
Posted by: KCL
Tue
12 May 2015
Entanglement entropy in a holographic model of the Kondo effect
Mario Flory
(Max-Planck Institute)
Abstract:
My starting point is a holographic model of the Kondo effect recently proposed by Erdmenger et. al., i.e. of a magnetic impurity interacting with a strongly coupled system. Specifically, I focus on the challenges of computing gravitational backreaction in this model, which demands a study of the Israel junction conditions. I present general results on these junction conditions, including analytical solutions for certain toy models, that may be relevant also more generally in the AdS/boundary CFT correspondence. Furthermore, similar junction conditions for a bulk Chern-Simons field appearing in the holographic Kondo model are discussed. I then focus on the computation and interpretation of entanglement entropy in this holographic model.
My starting point is a holographic model of the Kondo effect recently proposed by Erdmenger et. al., i.e. of a magnetic impurity interacting with a strongly coupled system. Specifically, I focus on the challenges of computing gravitational backreaction in this model, which demands a study of the Israel junction conditions. I present general results on these junction conditions, including analytical solutions for certain toy models, that may be relevant also more generally in the AdS/boundary CFT correspondence. Furthermore, similar junction conditions for a bulk Chern-Simons field appearing in the holographic Kondo model are discussed. I then focus on the computation and interpretation of entanglement entropy in this holographic model.
Posted by: IC
Thu
7 May 2015
Supersymmetric gauge theories on five-manifolds
Paul Richmond
(Oxford)
Abstract:
I will discuss how to construct rigid supersymmetric gauge theories on Riemannian five-manifolds following a holographic approach. This approach realises the five-manifold as the conformal boundary of a six-dimensional bulk supergravity solution and leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. The background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Finally, I’ll also construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.
I will discuss how to construct rigid supersymmetric gauge theories on Riemannian five-manifolds following a holographic approach. This approach realises the five-manifold as the conformal boundary of a six-dimensional bulk supergravity solution and leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. The background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Finally, I’ll also construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.
Posted by: QMW
Wed
6 May 2015
Superconformal Quantum Mechanics, Integrability and Discrete Light-Cone Quantisation
📍 London
Nick Dorey
(DAMTP Cambridge)
Abstract:
I will discuss recent progress in formulating superconformal quantum mechanics models which describe the (2,0) theory and N=4 super Yang-Mills in discrete light-cone quantisation.
I will discuss recent progress in formulating superconformal quantum mechanics models which describe the (2,0) theory and N=4 super Yang-Mills in discrete light-cone quantisation.
Posted by: KCL
Wed
6 May 2015
Introduction to Topological Strings
Omar Foda
(University of Melbourne)
Abstract:
ps. Prof. Foda will give an introduction to topological string theory and minimal models in the first hour or so before launching into his more technical topic.
ps. Prof. Foda will give an introduction to topological string theory and minimal models in the first hour or so before launching into his more technical topic.
Posted by: KCL
Wed
6 May 2015
Topological strings and minimal models
Omar Foda
(University of Melbourne)
Abstract:
I would like to explain, with emphasis on computational details, how one starts
from the refined topological vertex, constructs a topological partition function,
and chooses the parameters of the latter to obtain conformal blocks of Virasoro
minimal models.
I would like to explain, with emphasis on computational details, how one starts
from the refined topological vertex, constructs a topological partition function,
and chooses the parameters of the latter to obtain conformal blocks of Virasoro
minimal models.
Posted by: KCL
April 2015
Thu
30 Apr 2015
Hidden symmetries of scattering amplitudes (and of Hydrogen atom)
Simon Caron-Huot
(NBI)
Abstract:
Physical systems with unexpected, or `hidden,’ symmetries have often played an important role in physics, beginning with the classical Kepler problem whose Laplace-Runge-Lenz vector ensures the closure of planetary orbits,
and degeneracies of the Hydrogen spectrum. I will describe how precisely the same symmetry governs a unique four-dimensional quantum field theory, a maximally supersymmetric (`N=4') cousin of the strong-interaction Yang-Mills theory.
After reviewing progress in recent years in using these symmetries to solve this model, I will describe novel applications involving massive particles.
Combining the Laplace-Runge-Lenz vector with relativity then yields a novel way to calculate the spectrum of its Hydrogen-like bound states, including relativistic corrections. Based on 1408.0296.
Physical systems with unexpected, or `hidden,’ symmetries have often played an important role in physics, beginning with the classical Kepler problem whose Laplace-Runge-Lenz vector ensures the closure of planetary orbits,
and degeneracies of the Hydrogen spectrum. I will describe how precisely the same symmetry governs a unique four-dimensional quantum field theory, a maximally supersymmetric (`N=4') cousin of the strong-interaction Yang-Mills theory.
After reviewing progress in recent years in using these symmetries to solve this model, I will describe novel applications involving massive particles.
Combining the Laplace-Runge-Lenz vector with relativity then yields a novel way to calculate the spectrum of its Hydrogen-like bound states, including relativistic corrections. Based on 1408.0296.
Posted by: QMW
Thu
30 Apr 2015
Correlation functions of conserved currents in 3-dimensional superconformal theories
Evgeny Buchbinder
(University of Western Australia)
Wed
29 Apr 2015
Supersymmetric gauge theories on five-manifolds
Paul Richmond
(Oxford)
Abstract:
I will discuss how to construct rigid supersymmetric gauge theories on Riemannian five-manifolds following a holographic approach. This approach realises the five-manifold as the conformal boundary of a six-dimensional bulk supergravity solution and leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. The background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Finally, I’ll also construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.
I will discuss how to construct rigid supersymmetric gauge theories on Riemannian five-manifolds following a holographic approach. This approach realises the five-manifold as the conformal boundary of a six-dimensional bulk supergravity solution and leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. The background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Finally, I’ll also construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.
Posted by: IC
Thu
23 Apr 2015
Double Field Theory and Stringy Geometry
Chris Hull
(Imperial College)
Abstract:
One of the ways in which string theory differs from conventional field theories is that it has duality symmetries, which allow the construction of so-called non-geometric backgrounds, such as T-folds which have T-duality transition functions. String theory on a torus requires the introduction of dual coordinates conjugate to string winding number. This leads to physics and novel geometry in a doubled space, with non-trivial dynamics in the full doubled space-time. The geometry and physics of doubled space-time will be developed and discussed.
One of the ways in which string theory differs from conventional field theories is that it has duality symmetries, which allow the construction of so-called non-geometric backgrounds, such as T-folds which have T-duality transition functions. String theory on a torus requires the introduction of dual coordinates conjugate to string winding number. This leads to physics and novel geometry in a doubled space, with non-trivial dynamics in the full doubled space-time. The geometry and physics of doubled space-time will be developed and discussed.
Posted by: QMW
Thu
9 Apr 2015
Spectral Networks: Extensions and Applications
Pietro Longhi
(Rutgers University)
Abstract:
The BPS spectra of Class S theories are among the best understood, thanks in part to a construction known as Spectral Networks. We will review this framework and recent developments of it, and present results obtained through their applications.
The BPS spectra of Class S theories are among the best understood, thanks in part to a construction known as Spectral Networks. We will review this framework and recent developments of it, and present results obtained through their applications.
Posted by: QMW
Wed
8 Apr 2015
Polygon Seminar: Scattering amplitudes, super-Wilson loops and their symmetries
📍 London
Cristian Vergu
(King's College London)
Abstract:
I will give a pedagogical introduction to recent developments
in the study of N=4 super-Yang-Mills scattering amplitudes, and
super-Wilson loops with a focus on their symmetries.
I will give a pedagogical introduction to recent developments
in the study of N=4 super-Yang-Mills scattering amplitudes, and
super-Wilson loops with a focus on their symmetries.
Posted by: KCL
March 2015
Mon
30 Mar 2015
Graduate Lectures: M-theory
David Berman
(QMUL)
Abstract:
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Posted by: QMW
Thu
26 Mar 2015
Higher Gauge Theory and M-Theory
Christian Saemann
(Edinburgh)
Abstract:
Higher Gauge Theory is a categorical way of thinking about parallel transport
of extended objects. Such parallel transport appears naturally within string
and M-theory. In particular, the six-dimensional maximally superconformal
theory or at least self-dual strings in four dimensions should be captured by
Higher Gauge Theory. I will review some of my recent work in this area,
including how M2-brane models fit into the picture, how twistor geometry can
yield field equations containing the non-abelian tensor multiplet and give
explicit higher versions of the BPST instanton and the 't Hooft-Polyakov
monopole. If time permits, I will also talk a bit about a higher version of
the IKKT matrix model.
Higher Gauge Theory is a categorical way of thinking about parallel transport
of extended objects. Such parallel transport appears naturally within string
and M-theory. In particular, the six-dimensional maximally superconformal
theory or at least self-dual strings in four dimensions should be captured by
Higher Gauge Theory. I will review some of my recent work in this area,
including how M2-brane models fit into the picture, how twistor geometry can
yield field equations containing the non-abelian tensor multiplet and give
explicit higher versions of the BPST instanton and the 't Hooft-Polyakov
monopole. If time permits, I will also talk a bit about a higher version of
the IKKT matrix model.
Posted by: QMW
Wed
25 Mar 2015
E11 and Generalised Space-time
📍 London
Peter West
(King's College)
Abstract:
It has been conjectured that the fundamental theory of strings and branes has an \(E_{11}\) symmetry. I will explain how this conjecture leads to a generalized space-time, which is automatically equipped with its own geometry, as well as equations of motion for the fields that live on this generalized space-time.
It has been conjectured that the fundamental theory of strings and branes has an \(E_{11}\) symmetry. I will explain how this conjecture leads to a generalized space-time, which is automatically equipped with its own geometry, as well as equations of motion for the fields that live on this generalized space-time.
Posted by: KCL
Wed
18 Mar 2015
The Superconformal Bootstrap Program
📍 London
Balt Van Rees
(CERN)
Abstract:
In the past few years we have seen that the bootstrap approach to higher-dimensional conformal field theories (CFTs) can be surprisingly powerful. In particular, we are finally able to put the crossing symmetry equations to good use and extract nontrivial information about the spectrum and three-point functions in a generic CFT. In this talk I will discuss the application of these ideas to superconformal field theories, focussing on N=2 and N=4 theories in four dimensions. In those theories there exists a subsector where the crossing symmetry equations can be solved analytically. Together with the numerical analysis of the remaining constraints we can learn a great deal about the nonperturbative structure of these superconformal field theories.
In the past few years we have seen that the bootstrap approach to higher-dimensional conformal field theories (CFTs) can be surprisingly powerful. In particular, we are finally able to put the crossing symmetry equations to good use and extract nontrivial information about the spectrum and three-point functions in a generic CFT. In this talk I will discuss the application of these ideas to superconformal field theories, focussing on N=2 and N=4 theories in four dimensions. In those theories there exists a subsector where the crossing symmetry equations can be solved analytically. Together with the numerical analysis of the remaining constraints we can learn a great deal about the nonperturbative structure of these superconformal field theories.
Posted by: KCL
Wed
18 Mar 2015
Partition function on Hopf surfaces and Casimir energy
Benjamin Assel
(Kings College)
Abstract:
I will discuss the partition function of 4d N=1 theories on Hopf surfaces. These are diffeomorphic to S^1 x S^3 and the partition function provides a path integral realization of the supersymmetric index. Its large S^1 limit exhibits a universal behaviour associated to the existence of a Casimir energy. I will argue that, contrarily to the non-supersymmetric case, this Casimir energy is a physical (non-ambiguous) quantity in supersymmetric theories.
I will discuss the partition function of 4d N=1 theories on Hopf surfaces. These are diffeomorphic to S^1 x S^3 and the partition function provides a path integral realization of the supersymmetric index. Its large S^1 limit exhibits a universal behaviour associated to the existence of a Casimir energy. I will argue that, contrarily to the non-supersymmetric case, this Casimir energy is a physical (non-ambiguous) quantity in supersymmetric theories.
Posted by: IC
Thu
12 Mar 2015
On type II string theory on AdS3 times S3 times T4 and its CFT dual
Ofer Aharony
(Weizmann Institute)
Abstract:
I will review and discuss in detail type II string theory on \(AdS_3\times S^3\times T^4\) and its \(1+1\) dimensional superconformal field theory dual, emphasizing the string theoretic aspects of this duality. For one unit of NS-NS 5-brane flux (\(Q_5=1\)), this string theory has been suggested to be dual to a grand-canonical ensemble of \(T^{4N}/S_N\) free symmetric orbifold CFTs, and one goal will be to understand how this is consistent and how it fits with the description of other values of \(Q_5\). I will discuss how the strong coupling limit of the NS-NS string theory arises (even at large \(N\)) in the free orbifold description, and why this limit does not have a weakly coupled R-R description. The dual CFT includes (for all values of \(Q_5\)) an extra \(T^4\) factor that is decoupled from perturbative string theory, and I will discuss how this appears and how it is coupled to the CFT. Based on 2406.14605 with Erez Urbach.
I will review and discuss in detail type II string theory on \(AdS_3\times S^3\times T^4\) and its \(1+1\) dimensional superconformal field theory dual, emphasizing the string theoretic aspects of this duality. For one unit of NS-NS 5-brane flux (\(Q_5=1\)), this string theory has been suggested to be dual to a grand-canonical ensemble of \(T^{4N}/S_N\) free symmetric orbifold CFTs, and one goal will be to understand how this is consistent and how it fits with the description of other values of \(Q_5\). I will discuss how the strong coupling limit of the NS-NS string theory arises (even at large \(N\)) in the free orbifold description, and why this limit does not have a weakly coupled R-R description. The dual CFT includes (for all values of \(Q_5\)) an extra \(T^4\) factor that is decoupled from perturbative string theory, and I will discuss how this appears and how it is coupled to the CFT. Based on 2406.14605 with Erez Urbach.
Posted by: IC2
Thu
12 Mar 2015
Gluon scattering amplitudes as flux-tube partition functions
Benjamin Basso
(ENS Paris)
Abstract:
In this talk I will explain how to compute gluon scattering
amplitudes at finite coupling in planar N=4 SYM theory, using the duality
with null polygonal Wilson loops, conformal symmetry, and the
integrability of the colour flux tube dynamics. After introducing the main
ideas and results, I will present some applications of this formalism at
strong coupling and discuss the validity of the semiclassical (dual)
string description.
In this talk I will explain how to compute gluon scattering
amplitudes at finite coupling in planar N=4 SYM theory, using the duality
with null polygonal Wilson loops, conformal symmetry, and the
integrability of the colour flux tube dynamics. After introducing the main
ideas and results, I will present some applications of this formalism at
strong coupling and discuss the validity of the semiclassical (dual)
string description.
Posted by: QMW
Wed
11 Mar 2015
On conformal windows and the phase structure of 2+1d and 3+1d QCD
Ofer Aharony
(Weizmann Institute)
Abstract:
Many gauge theories, such as 3+1d and 2+1d SU(N) gauge theories with N_f massless Dirac fermions in the fundamental representation, exhibit "conformal windows" - a range of values of N_f for which the theory flows to a non-trivial conformal field theory at low energy. It is interesting to ask how these windows end and transition into phases with confinement and with spontaneous breaking of the flavor symmetry. I will begin by reviewing what is known about 3+1 dimensional QCD, focusing on the large N and N_f limit and on the conformal window there, and I will review the standard "merger scenario" for the end of its conformal window.
I will then move on to QCD in 2+1 dimensions, and discuss its phase diagram as a function of the mass and of the discrete parameters N, N_f and the Chern-Simons level k, focusing again on the limit of large N, N_f, k. I will argue that this theory also has a conformal window (corresponding to a second order phase transition when changing the mass) but that it does not always end at a merger, and I will suggest two other possibilities for the end of general conformal windows. The different scenarios can be distinguished by the behavior of the theory as the boundary of the conformal window is approached from either side. Based on work in progress with Thomas Dumitrescu, Zohar Komargodski and Jiangyuan Qian.
Many gauge theories, such as 3+1d and 2+1d SU(N) gauge theories with N_f massless Dirac fermions in the fundamental representation, exhibit "conformal windows" - a range of values of N_f for which the theory flows to a non-trivial conformal field theory at low energy. It is interesting to ask how these windows end and transition into phases with confinement and with spontaneous breaking of the flavor symmetry. I will begin by reviewing what is known about 3+1 dimensional QCD, focusing on the large N and N_f limit and on the conformal window there, and I will review the standard "merger scenario" for the end of its conformal window.
I will then move on to QCD in 2+1 dimensions, and discuss its phase diagram as a function of the mass and of the discrete parameters N, N_f and the Chern-Simons level k, focusing again on the limit of large N, N_f, k. I will argue that this theory also has a conformal window (corresponding to a second order phase transition when changing the mass) but that it does not always end at a merger, and I will suggest two other possibilities for the end of general conformal windows. The different scenarios can be distinguished by the behavior of the theory as the boundary of the conformal window is approached from either side. Based on work in progress with Thomas Dumitrescu, Zohar Komargodski and Jiangyuan Qian.
Posted by: IC2
Wed
11 Mar 2015
Multiboundary wormholes and holographic entanglement
Simon Ross
(Durham)
Wed
11 Mar 2015
Holography for N=2(star) on S4
Nikolay Bobev
(Leuven)
Abstract:
I will discuss the gravitational dual of a mass deformation of N=4 SYM, called N=2* SYM, on S^4. Using holographic techniques one can calculate the universal contribution to the corresponding free energy in the planar limit and at large 't Hooft coupling. The result matches the expression recently computed using supersymmetric localization in the field theory. This agreement constitutes a non-trivial precision test of holography in a non-conformal setting. I will also briefly discuss the extension of these results to mass deformations of N=4 SYM with N=1 supersymmetry.
I will discuss the gravitational dual of a mass deformation of N=4 SYM, called N=2* SYM, on S^4. Using holographic techniques one can calculate the universal contribution to the corresponding free energy in the planar limit and at large 't Hooft coupling. The result matches the expression recently computed using supersymmetric localization in the field theory. This agreement constitutes a non-trivial precision test of holography in a non-conformal setting. I will also briefly discuss the extension of these results to mass deformations of N=4 SYM with N=1 supersymmetry.
Posted by: QMW
Mon
9 Mar 2015
Graduate Lectures: M-theory
David Berman
(QMUL)
Abstract:
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Posted by: QMW
Thu
5 Mar 2015
Permutation orbifolds and holography
Mukund Rangamani
(Durham)
Abstract:
CFTs at large central charge display some universal features which can be inferred from holography. Using these as a guide one can obtain some necessary conditions for a given CFT to admit a classical string dual. I will describe attempts to construct a large class of CFTs satisfying these conditions exploiting some technology of permutation orbifolds.
CFTs at large central charge display some universal features which can be inferred from holography. Using these as a guide one can obtain some necessary conditions for a given CFT to admit a classical string dual. I will describe attempts to construct a large class of CFTs satisfying these conditions exploiting some technology of permutation orbifolds.
Posted by: QMW
Wed
4 Mar 2015
High energy scattering in string theory
📍 London
Rodolfo Russo
(Queen Mary University)
Abstract:
The study of high energy amplitudes in string theory provides an interesting arena to study several issues in quantum theories of gravity. I will focus on a conceptually very simple situation where a perturbative graviton scatters against a stack of D-branes and I will discuss phenomena, such as the emergence of tidal forces, the restoration of unitarity through resummation of diagrams and how the Regge behaviour of string theory is crucial to avoid causality violations
The study of high energy amplitudes in string theory provides an interesting arena to study several issues in quantum theories of gravity. I will focus on a conceptually very simple situation where a perturbative graviton scatters against a stack of D-branes and I will discuss phenomena, such as the emergence of tidal forces, the restoration of unitarity through resummation of diagrams and how the Regge behaviour of string theory is crucial to avoid causality violations
Posted by: KCL
Wed
4 Mar 2015
Lessons from crossing symmetry at large N
Tomasz Lukowski
(Oxford)
Abstract:
In this talk I will discuss how to construct all solutions consistent with crossing symmetry in the limit of large central charge c ~ N^2, starting from the four-point correlator of the stress tensor multiplet in N=4 SYM. Unitarity forces the introduction of a scale \Delta_{gap} and these solutions organize as a double expansion in 1/c and 1/\Delta_{gap}. These solutions are valid to leading order in 1/c and to all orders in 1/\Delta_{gap} and reproduce, in particular, instanton corrections previously found. Comparison with such instanton computations allows to fix \Delta_{gap}. Using this gap scale one can explain the upper bounds for the scaling dimension of unprotected operators observed in the numerical superconformal bootstrap at large central charge.
In this talk I will discuss how to construct all solutions consistent with crossing symmetry in the limit of large central charge c ~ N^2, starting from the four-point correlator of the stress tensor multiplet in N=4 SYM. Unitarity forces the introduction of a scale \Delta_{gap} and these solutions organize as a double expansion in 1/c and 1/\Delta_{gap}. These solutions are valid to leading order in 1/c and to all orders in 1/\Delta_{gap} and reproduce, in particular, instanton corrections previously found. Comparison with such instanton computations allows to fix \Delta_{gap}. Using this gap scale one can explain the upper bounds for the scaling dimension of unprotected operators observed in the numerical superconformal bootstrap at large central charge.
Posted by: IC
Wed
4 Mar 2015
Graduate Lectures: M-theory
David Berman
(QMUL)
Abstract:
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Posted by: QMW
February 2015
Wed
25 Feb 2015
Superconformal Quantum Mechanics, Integrability and Discrete Light-Cone Quantisation
📍 London
Nick Dorey
(DAMTP Cambridge)
Abstract:
I will discuss recent progress in formulating superconformal quantum mechanics models which describe the (2,0) theory and N=4 super Yang-Mills in discrete light-cone quantisation.
I will discuss recent progress in formulating superconformal quantum mechanics models which describe the (2,0) theory and N=4 super Yang-Mills in discrete light-cone quantisation.
Posted by: KCL
Wed
25 Feb 2015
Supergravity as a Consistent Quantum Theory?
Tristan Dennen
(NBI)
Abstract:
Supergravity theories were once hoped to provide ultraviolet finite theories of quantum gravity without requiring profoundly new physical frameworks. These hopes faded in the 1980s, but renewed efforts in recent years have uncovered some surprising ultraviolet behaviour. In this talk, I will give an overview of the explicit scattering amplitude calculations in perturbative supergravity over the last few years. In particular cases, there are indications of ultraviolet cancellations not accounted for by known symmetry arguments. I will highlight these cases and give some reasons to be optimistic and some reasons to be pessimistic about supergravity as a contender for a quantum theory of gravity.
Supergravity theories were once hoped to provide ultraviolet finite theories of quantum gravity without requiring profoundly new physical frameworks. These hopes faded in the 1980s, but renewed efforts in recent years have uncovered some surprising ultraviolet behaviour. In this talk, I will give an overview of the explicit scattering amplitude calculations in perturbative supergravity over the last few years. In particular cases, there are indications of ultraviolet cancellations not accounted for by known symmetry arguments. I will highlight these cases and give some reasons to be optimistic and some reasons to be pessimistic about supergravity as a contender for a quantum theory of gravity.
Posted by: IC
Wed
25 Feb 2015
Graduate Lectures: M-theory
David Berman
(QMUL)
Abstract:
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Graduate Lectures: This short course will cover the origin of M-theory and brane physics with its applications.
Posted by: QMW
Thu
19 Feb 2015
Quantum Gravity and the Stbility of the Higgs Vacuum
Jan Plefka
(Humboldt)
Abstract:
A central outcome of the recent Higgs discovery is that the Standard Model (SM) appears to be a selfconsistent quantum field theory all the way up to the
Planck scale. Moreover, the measured values for the Higgs and top masses have an intriguing consequence for the question of stability of the Higgs
vacuum: The SM lies close to the border of absolute electroweak vacuum stability and metastability. However, these celebrated results extrapolate the SM into a region
where quantum gravity effects become important. We have therefore computed the quantum gravitational contributions to the standard model effective potential and
analyzed their effects on the Higgs vacuum stability in the framework of effective field theory. Non-renormalizability of Einstein gravity induces higher dimension φ6 and φ8
operators at the one- loop level with novel couplings η1/2. We find that the true minimum of the standard model effective potential now lies below the Planck scale for almost
the entire parameter space (η1/2(mt) > 0.01). In addition quantum gravity is shown to contribute to the minimal value of the standard model NLO effective potential at the percent level.
The quantum gravity induced contributions yield a metastable vacuum for a large fraction of the parameter space in the flowing couplings η1/2.
A central outcome of the recent Higgs discovery is that the Standard Model (SM) appears to be a selfconsistent quantum field theory all the way up to the
Planck scale. Moreover, the measured values for the Higgs and top masses have an intriguing consequence for the question of stability of the Higgs
vacuum: The SM lies close to the border of absolute electroweak vacuum stability and metastability. However, these celebrated results extrapolate the SM into a region
where quantum gravity effects become important. We have therefore computed the quantum gravitational contributions to the standard model effective potential and
analyzed their effects on the Higgs vacuum stability in the framework of effective field theory. Non-renormalizability of Einstein gravity induces higher dimension φ6 and φ8
operators at the one- loop level with novel couplings η1/2. We find that the true minimum of the standard model effective potential now lies below the Planck scale for almost
the entire parameter space (η1/2(mt) > 0.01). In addition quantum gravity is shown to contribute to the minimal value of the standard model NLO effective potential at the percent level.
The quantum gravity induced contributions yield a metastable vacuum for a large fraction of the parameter space in the flowing couplings η1/2.
Posted by: QMW
Wed
18 Feb 2015
Revisiting soliton contributions to perturbative amplitudes
📍 London
Costis Papageorgakis
(Queen Mary University)
Abstract:
It is often said that soliton contributions to perturbative processes in QFT are exponentially suppressed by a form-factor. We will provide a derivation of this form-factor by studying the soliton-antisoliton pair-production amplitude. This reduces to the calculation of a matrix element in the quantum mechanics on the soliton moduli space. We will investigate the conditions under which the latter leads to suppression. Extending this framework to instanton-solitons in five-dimensional Yang-Mills theory leaves open the possibility that such contributions will not be suppressed.
It is often said that soliton contributions to perturbative processes in QFT are exponentially suppressed by a form-factor. We will provide a derivation of this form-factor by studying the soliton-antisoliton pair-production amplitude. This reduces to the calculation of a matrix element in the quantum mechanics on the soliton moduli space. We will investigate the conditions under which the latter leads to suppression. Extending this framework to instanton-solitons in five-dimensional Yang-Mills theory leaves open the possibility that such contributions will not be suppressed.
Posted by: KCL
Wed
18 Feb 2015
lambda-deformations
Kostas Sfetsos
(University of Athens)
Abstract:
We review the construction of the so-called λ-deformations of WZW and gauged WZW models. We discuss their integrability and algebraic properties, their behavior under RG flows as well as their embeddings to type-II supergravity.
We review the construction of the so-called λ-deformations of WZW and gauged WZW models. We discuss their integrability and algebraic properties, their behavior under RG flows as well as their embeddings to type-II supergravity.
Posted by: IC
Thu
12 Feb 2015
Constraining Asymptotically Safe Inflation with cosmological observations
Alfio Bonanno
(INAF/INFN)
Thu
12 Feb 2015
Extremal chiral ring states in AdS/CFT are described by free fermions
David Berenstein
(UCSB)
Abstract:
Half BPS states (operators) in N=4 SYM are famously described by free fermions both at weak and strong coupling. I describe a set of conjectures for a preferred class of states in more general conformal field theories that can be tested in supergravity for when such a free fermion description might arise and some motivation for it applying generally. The states in question belong to the chiral ring of a supersymmetric conformal field theory that extremize an additional U(1) charge for fixed dimension and can be reduced to multi-traces of a composite matrix field, which is equivalent to using Young tableaux (Schur polynomials) as a basis. The main conjecture asserts that
if the Young tableaux are orthogonal, then the set of extremal three point functions of traces to order 1/N are determined up to a single constant. The conjecture is extended further by providing an exact norm for the Schur basis and this norm arises from a set of free fermions for a generalized oscillator algebra.
Half BPS states (operators) in N=4 SYM are famously described by free fermions both at weak and strong coupling. I describe a set of conjectures for a preferred class of states in more general conformal field theories that can be tested in supergravity for when such a free fermion description might arise and some motivation for it applying generally. The states in question belong to the chiral ring of a supersymmetric conformal field theory that extremize an additional U(1) charge for fixed dimension and can be reduced to multi-traces of a composite matrix field, which is equivalent to using Young tableaux (Schur polynomials) as a basis. The main conjecture asserts that
if the Young tableaux are orthogonal, then the set of extremal three point functions of traces to order 1/N are determined up to a single constant. The conjecture is extended further by providing an exact norm for the Schur basis and this norm arises from a set of free fermions for a generalized oscillator algebra.
Posted by: QMW
Wed
11 Feb 2015
Higher Spins and Strings
Matthias Gaberdiel
(ETH Zurich)
Abstract:
The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the
evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how
this relation fits into the framework of the familiar stringy AdS/CFT correspondence.
The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the
evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how
this relation fits into the framework of the familiar stringy AdS/CFT correspondence.
Posted by: KCL
Tue
10 Feb 2015
Conformal symmetry and smoothness
George Papadopoulos
(King's)
Abstract:
I shall explain why there is symmetry enhancement near black hole and brane horizons. I shall also present some applications which include the classification of AdS backgrounds in supergravity.
I shall explain why there is symmetry enhancement near black hole and brane horizons. I shall also present some applications which include the classification of AdS backgrounds in supergravity.
Posted by: KCL
Thu
5 Feb 2015
Introduction to pure spinor methods for string- and field-theory amplitudes
Oliver Schlotterer
(AEI Potsdam)
Abstract:
In this talk, I will review basic features of the pure spinor superstring as well as recent progress to compute and compactly represent scattering amplitudes in this framework. A string-inspired organization scheme for amplitudes in both field- and string-theories will be described where the non-linearities of ten-dimensional super Yang-Mills theory are encoded in so-called multiparticle superfields. They allow to efficiently capture the polarization dependence through cubic diagrams where the intuitive mapping as well as the composition rules for amplitudes are guided by BRST invariance.
In this talk, I will review basic features of the pure spinor superstring as well as recent progress to compute and compactly represent scattering amplitudes in this framework. A string-inspired organization scheme for amplitudes in both field- and string-theories will be described where the non-linearities of ten-dimensional super Yang-Mills theory are encoded in so-called multiparticle superfields. They allow to efficiently capture the polarization dependence through cubic diagrams where the intuitive mapping as well as the composition rules for amplitudes are guided by BRST invariance.
Posted by: QMW
Wed
4 Feb 2015
Self-Dual Higher Gauge Theory
📍 London
Martin Wolf
(University of Surrey)
Abstract:
I will review recent work on the formulation of self-dual higher (categorified) gauge theory in six dimensions using twistor theory.
I will review recent work on the formulation of self-dual higher (categorified) gauge theory in six dimensions using twistor theory.
Posted by: KCL
Wed
4 Feb 2015
New AdS/CFT duals through non-Abelian T-duality
Yolanda Lozano
(Oviedo)
Abstract:
We will present new AdS_6 and AdS_4 backgrounds constructed using non-Abelian T-duality on known solutions and discuss some properties of the dual CFTs associated to these backgrounds.
We will present new AdS_6 and AdS_4 backgrounds constructed using non-Abelian T-duality on known solutions and discuss some properties of the dual CFTs associated to these backgrounds.
Posted by: IC
Wed
4 Feb 2015
Aspects of Gauge-Strings Duality
Carlos Nunez
(Swansea U.)
Abstract:
I will discuss recent developments in the duality between gauge fields and strings.
I will discuss recent developments in the duality between gauge fields and strings.
Posted by: QMW
January 2015
Thu
29 Jan 2015
Higher Spin Holography
Robert de Mello Koch
(Witwatersrand U.)
Abstract:
In this talk we will discuss the collective field theory approach towards
understanding the holographic duality between Vasiliev's minimal higher
spin theory in AdS4 and the free O(N) vector model in 2+1 dimensions.
In this talk we will discuss the collective field theory approach towards
understanding the holographic duality between Vasiliev's minimal higher
spin theory in AdS4 and the free O(N) vector model in 2+1 dimensions.
Posted by: QMW
Wed
28 Jan 2015
Integrability and the Conformal Field Theory of the Higgs branch
📍 London
Bogdan Stefanski
(City University)
Abstract:
I will review how integrability can be used to understand the spectral problem (including massless modes) of Type IIB string theory on AdS3 x S3 x T4 with R-R flux. I will then show how integrability emerges in the dual CFT2. This provides arguably the first non-BPS test of the planar AdS3/CFT2 correspondence in the literature and gives strong evidence in identifying particular points in the moduli space of the dual theories.
I will review how integrability can be used to understand the spectral problem (including massless modes) of Type IIB string theory on AdS3 x S3 x T4 with R-R flux. I will then show how integrability emerges in the dual CFT2. This provides arguably the first non-BPS test of the planar AdS3/CFT2 correspondence in the literature and gives strong evidence in identifying particular points in the moduli space of the dual theories.
Posted by: KCL
Wed
28 Jan 2015
Euclidean Quantum Supergravity
David Tong
(Cambridge)
Abstract:
I'll revisit some old of ideas of Euclidean quantum gravity, in
which manifolds of different topology are summed in the path integral.
I'll show that, in certain circumstances, gravitational instantons can
destabilise supersymmetric Kaluza-Klein compactifications. We'll also see
how one-loop divergences in quantum gravity can be subsumed into a new
RG-invariant topological scale.
I'll revisit some old of ideas of Euclidean quantum gravity, in
which manifolds of different topology are summed in the path integral.
I'll show that, in certain circumstances, gravitational instantons can
destabilise supersymmetric Kaluza-Klein compactifications. We'll also see
how one-loop divergences in quantum gravity can be subsumed into a new
RG-invariant topological scale.
Posted by: IC
Wed
28 Jan 2015
On black hole thermodynamics from super Yang-Mills
Toby Wiseman
(Imperial College)
Abstract:
I will review the link between 1+p dimensional maximally supersymmetric Yang-Mills and the black hole thermodynamics of Dp-branes via the gauge/string correspondence. The finite temperature behaviour of Dp-brane supergravity black holes looks very alien from the perspective of the dual strongly coupled Yang-Mills. However, I will argue that in a natural set of Yang-Mills variables, the classical moduli (which unfortunately are still strongly coupled), certain features of these thermodynamics become quite transparent.
I will review the link between 1+p dimensional maximally supersymmetric Yang-Mills and the black hole thermodynamics of Dp-branes via the gauge/string correspondence. The finite temperature behaviour of Dp-brane supergravity black holes looks very alien from the perspective of the dual strongly coupled Yang-Mills. However, I will argue that in a natural set of Yang-Mills variables, the classical moduli (which unfortunately are still strongly coupled), certain features of these thermodynamics become quite transparent.
Posted by: QMW
Thu
22 Jan 2015
Cancelled
Kyriakos Papadodimas
(CERN)
Wed
21 Jan 2015
Bootstrapping SCFTs with four supercharges
📍 London
Dalimil Mazac
(Perimeter Institute)
Abstract:
I will discuss conformal bootstrap for SCFTs with four supercharges (eight superconformal charges) between two and four dimensions in a unified language. The special cases of interest are (2,2) SCFTs in d=2, N=2 SCFTs in d=3, and N=1 SCFTs in d=4. I will show how a large class of superconformal blocks can be found from the Casimir differential equation. I will describe the numerical bounds arising from the two independent bootstrap equations of the four-point function involving a chiral field and its conjugate. The bound involves three kinks, one of which corresponds to the IR fixed point of the Wess-Zumino model, and the other two remain mysterious.
I will discuss conformal bootstrap for SCFTs with four supercharges (eight superconformal charges) between two and four dimensions in a unified language. The special cases of interest are (2,2) SCFTs in d=2, N=2 SCFTs in d=3, and N=1 SCFTs in d=4. I will show how a large class of superconformal blocks can be found from the Casimir differential equation. I will describe the numerical bounds arising from the two independent bootstrap equations of the four-point function involving a chiral field and its conjugate. The bound involves three kinks, one of which corresponds to the IR fixed point of the Wess-Zumino model, and the other two remain mysterious.
Posted by: KCL
Wed
21 Jan 2015
Polygon Seminar: Microscopic description of black holes in string theory
Sameer Murthy
(King's)
Abstract:
I will discuss the idea that a black hole in string theory is made up of a large number of microscopic constituents. For a class of black holes and black strings with extended supersymmetry, one has an exact counting formula for the number of states. I will sketch the idea and derivation of some of these formulas. I will then discuss applications to the AdS_2/CFT_1 and the AdS_3/CFT_2 correspondences.
I will discuss the idea that a black hole in string theory is made up of a large number of microscopic constituents. For a class of black holes and black strings with extended supersymmetry, one has an exact counting formula for the number of states. I will sketch the idea and derivation of some of these formulas. I will then discuss applications to the AdS_2/CFT_1 and the AdS_3/CFT_2 correspondences.
Posted by: KCL
Wed
14 Jan 2015
Deforming the AdS(5)xS(5) superstring inspired by Pohlmeyer reduction
Luis Miramontes
(Santiago)
Abstract:
The S-matrix of the world-sheet theory of the string in AdS(5)xS(5) is known
to admit a deformation where the original symmetry algebra is replaced by
the associated quantum group. The case where q, the deformation parameter,
is real has been identified as a particular deformation of the Green-Schwarz
sigma model known as the "eta-deformation". The case with q a root of unity
interpolates between the AdS(5)xS(5) world-sheet theory and its Pohlmeyer
reduction. However, an interpretation of this case is still lacking. We will
summarize recent work aimed to show that sigma models on (semi-)symmetric
spaces F/G admit discrete integrable deformations that can be viewed as
deformations of the F/F gauged WZW model. For the AdS(5)xS(5) world-sheet
theory, F=PSU(2,2|4) and the resulting theory has just the right amount of
kappa-symmetries, which points to the existence of a new fully consistent
deformed string background.
The S-matrix of the world-sheet theory of the string in AdS(5)xS(5) is known
to admit a deformation where the original symmetry algebra is replaced by
the associated quantum group. The case where q, the deformation parameter,
is real has been identified as a particular deformation of the Green-Schwarz
sigma model known as the "eta-deformation". The case with q a root of unity
interpolates between the AdS(5)xS(5) world-sheet theory and its Pohlmeyer
reduction. However, an interpretation of this case is still lacking. We will
summarize recent work aimed to show that sigma models on (semi-)symmetric
spaces F/G admit discrete integrable deformations that can be viewed as
deformations of the F/F gauged WZW model. For the AdS(5)xS(5) world-sheet
theory, F=PSU(2,2|4) and the resulting theory has just the right amount of
kappa-symmetries, which points to the existence of a new fully consistent
deformed string background.
Posted by: IC
Thu
8 Jan 2015
Functional determinants, index theorems and exact quantum black hole entropy.
Sameer Murthy
(King's)
Abstract:
I will discuss the exact quantum entropy of supersymmetric black holes as a gravitational functional integral in AdS2. In theories with eight supercharges, a computation of the exact entropy is possible using supersymmetric localization. I will discuss this technique, and describe the computation of functional determinants that can be computed using index theorems. I will then compare the exact gravitational formula to microscopic formulas coming from string theory.
I will discuss the exact quantum entropy of supersymmetric black holes as a gravitational functional integral in AdS2. In theories with eight supercharges, a computation of the exact entropy is possible using supersymmetric localization. I will discuss this technique, and describe the computation of functional determinants that can be computed using index theorems. I will then compare the exact gravitational formula to microscopic formulas coming from string theory.
Posted by: QMW