Triangle Seminars
December 2004
Thu
16 Dec 2004
Heterotic String on Half-flat Manifolds
Andre Lukas
(Oxford)
Abstract:
We consider the heterotic string on certain six-dimensional half-flat manifolds which arise in the context of mirror symmetry. The four-dimensional N=1 effective theory is derived including the superpotential induced by the intrinsic torsion and NS NS flux. From the calculation of the gravitino mass term, we also obtain a general Gukov type formula valid for all heterotic compactifications
on manifolds with SU(3) structure. The results are used to study heterotic AdS4 vacua which arise from the flux superpotential combined with gaugino condensation.
We consider the heterotic string on certain six-dimensional half-flat manifolds which arise in the context of mirror symmetry. The four-dimensional N=1 effective theory is derived including the superpotential induced by the intrinsic torsion and NS NS flux. From the calculation of the gravitino mass term, we also obtain a general Gukov type formula valid for all heterotic compactifications
on manifolds with SU(3) structure. The results are used to study heterotic AdS4 vacua which arise from the flux superpotential combined with gaugino condensation.
Posted by: IC
Wed
15 Dec 2004
Supersymmetric string and geometries with torsion and special holonomy
📍 London
Stefan Ivanov
(University of Sofia)
Mon
13 Dec 2004
On the relation between Liouville theory and string theory in AdS3
📍 London
Sylvain Ribault
(KCL)
Abstract:
I explain how arbitrary correlators of string theory in the
Euclidean AdS3 can be computed from the correlators of Liouville theory.
This makes use of the KZ-BPZ correspondence, which relates on the one hand
the Knizhnik-Zamolodchikov equations reflecting the group symmetry in
AdS3, on the other hand the Belavin-Polyakov-Zamolodchikov equations
reflecting the presence of degenerate fields in the Liouville correlators.
I explain how arbitrary correlators of string theory in the
Euclidean AdS3 can be computed from the correlators of Liouville theory.
This makes use of the KZ-BPZ correspondence, which relates on the one hand
the Knizhnik-Zamolodchikov equations reflecting the group symmetry in
AdS3, on the other hand the Belavin-Polyakov-Zamolodchikov equations
reflecting the presence of degenerate fields in the Liouville correlators.
Posted by: KCL
Thu
9 Dec 2004
D-branes on threefolds and quiver sheaves
Balazs Szendroi
(Utrecht and Oxford)
Thu
9 Dec 2004
Gauge Theory Amplitudes, MHV rules and Twistor Space
Valentin Khoze
(Durham)
Abstract:
I will give an introduction to the novel method of calculating scattering amplitudes in gauge theory with twistor-space string theory inspired rules. I will show how the method works in simple cases and discuss recent new results for the amplitudes obtained at tree and loop level. I'll discuss some known puzzles, the ways to resolve them, open questions and future directions, including issues in string theory, quantum field theory and phenomenology.
I will give an introduction to the novel method of calculating scattering amplitudes in gauge theory with twistor-space string theory inspired rules. I will show how the method works in simple cases and discuss recent new results for the amplitudes obtained at tree and loop level. I'll discuss some known puzzles, the ways to resolve them, open questions and future directions, including issues in string theory, quantum field theory and phenomenology.
Posted by: IC
Wed
8 Dec 2004
Holographic RG Flows and Duality
Christian Romelsberger
(Perimeter institute)
Abstract:
This talk is part of the joint Triangular Seminars.
This talk is part of the joint Triangular Seminars.
Posted by: KCL
Wed
8 Dec 2004
Conformal defects as solution-generating symmetries for D-branes
Costas Bachas
(ENS Paris)
Abstract:
Using the example of WZW D-branes, I will explain how loop operators, corresponding to bulk conformal defects, generate new consistent D-branes from old ones. I will comment on possible extensions to more general geometries.
Using the example of WZW D-branes, I will explain how loop operators, corresponding to bulk conformal defects, generate new consistent D-branes from old ones. I will comment on possible extensions to more general geometries.
Posted by: KCL
Thu
2 Dec 2004
2D Yang-Mills Theory and Moduli Spaces of Holomorphic Differentials
Richard Szabo
(Heriot-Watt)
Thu
2 Dec 2004
A review of twistor string theory
Phillip Candelas
(Oxford)
Wed
1 Dec 2004
D-branes and BCFT in Hpp-wave backgrounds
📍 London
Giuseppe D'Appollonio
(KCL)
November 2004
Tue
30 Nov 2004
Calculating Dirac Observables from Partial Observables
Bianca Dittrich
(AEI Golm)
Abstract:
We will generalize the concept of partial and complete observables, intruduced by Rovelli, to constrained systems with an arbitrary number of (first class) constraints and to canonical field theories. Different methods to calculate complete observables (aka Dirac observables) will be presented and applied to examples, moreover their algebraic properties will be considered. Furthermore we will investigate whether it is possible to calculate complete observables in stages. In the case of gravity this will answer the question , whether it is possible to calculate the complete observable with respect to the Hamiltonian constraints, starting from 3-diffeomorphism invariant partial observables.
We will generalize the concept of partial and complete observables, intruduced by Rovelli, to constrained systems with an arbitrary number of (first class) constraints and to canonical field theories. Different methods to calculate complete observables (aka Dirac observables) will be presented and applied to examples, moreover their algebraic properties will be considered. Furthermore we will investigate whether it is possible to calculate complete observables in stages. In the case of gravity this will answer the question , whether it is possible to calculate the complete observable with respect to the Hamiltonian constraints, starting from 3-diffeomorphism invariant partial observables.
Posted by: KCL
Mon
29 Nov 2004
Correlation Functions in Holographic RG Flows
Ioannis Papadimitriou
(Amsterdam)
Abstract:
In the supergravity approximation of the AdS/CFT correspondence correlation fucntions of the strongly coupled gauge theory can be computed by evaluating the on-shell supergravity action with arbitrary Dirichlet boundary conditions for the various fields. It is well
known, however, that the on-shell action on the conformal boundary of AdS diverges due to the infinite volume of the bulk. Holographic Renormalization is a method for systematically constructing covariant counter terms which remove the divergences of the on-shell supergravity action for any asymptotically AdS space and it provides an algorithm for calculating renormalized correlation functions of the strongly coupled gauge theory. I will review the main steps involved in this algorithm and present a recently developed Hamiltonian version of the method where the AdS radius plays the role of time in the Hamiltonian formalism. I will then apply this method to calculate correlation functions in the field theory duals of various Poincare and AdS-sliced domain wall solutions of five dimensional gauged supergravity, including the recently discovered Janus background.
In the supergravity approximation of the AdS/CFT correspondence correlation fucntions of the strongly coupled gauge theory can be computed by evaluating the on-shell supergravity action with arbitrary Dirichlet boundary conditions for the various fields. It is well
known, however, that the on-shell action on the conformal boundary of AdS diverges due to the infinite volume of the bulk. Holographic Renormalization is a method for systematically constructing covariant counter terms which remove the divergences of the on-shell supergravity action for any asymptotically AdS space and it provides an algorithm for calculating renormalized correlation functions of the strongly coupled gauge theory. I will review the main steps involved in this algorithm and present a recently developed Hamiltonian version of the method where the AdS radius plays the role of time in the Hamiltonian formalism. I will then apply this method to calculate correlation functions in the field theory duals of various Poincare and AdS-sliced domain wall solutions of five dimensional gauged supergravity, including the recently discovered Janus background.
Posted by: IC
Fri
26 Nov 2004
Spacetime-filling branes in ten dimensions
Fabio Riccioni
(Cambridge)
Thu
25 Nov 2004
Glasses, at Random
📍 London
Reimer Kuehn
(Department of Mathematics, KCL)
Abstract:
The physics of glassy systems at low temperatures differs in striking and unexpected ways from that of their crystalline counterparts, in that thermal, transport and dynamic response properties exhibit unusual temperature variation. Atomic or molecular tunneling centers are believed to be at the origin of these phenomena, which show a remarkable degree of universality across a wide spectrum of diverse amorphous substances, ranging from window glass to polystyrene. We describe recent advances in understanding these phenomena, using a microscopic modelling approach. It has for the first time allowed to identify a mechanism responsible for the occurrence of tunneling systems, to characterize them quantitatively, and to provide a simple and transparent explanation for the unusual universality of glassy low temperature anomalies.
The physics of glassy systems at low temperatures differs in striking and unexpected ways from that of their crystalline counterparts, in that thermal, transport and dynamic response properties exhibit unusual temperature variation. Atomic or molecular tunneling centers are believed to be at the origin of these phenomena, which show a remarkable degree of universality across a wide spectrum of diverse amorphous substances, ranging from window glass to polystyrene. We describe recent advances in understanding these phenomena, using a microscopic modelling approach. It has for the first time allowed to identify a mechanism responsible for the occurrence of tunneling systems, to characterize them quantitatively, and to provide a simple and transparent explanation for the unusual universality of glassy low temperature anomalies.
Posted by: KCL
Thu
25 Nov 2004
Twistor-inspired approach to super Yang-Mills
Bill Spence
(QMW)
Abstract:
Witten's twistor string theory description of N=4 super Yang-Mills has led to much progress in perturbative Yang-Mills theory this year, with accumulating evidence for the localisation of scattering amplitudes in twistor space in various Yang-Mills theories. This talk will focus on the MHV diagram approach, which builds in localisation, and will describe work done at Queen Mary which shows how to define MHV diagrams at loop level. This has been successfully applied to give the general one-loop MHV amplitudes in N=4 and N=1 super Yang-Mills.
Witten's twistor string theory description of N=4 super Yang-Mills has led to much progress in perturbative Yang-Mills theory this year, with accumulating evidence for the localisation of scattering amplitudes in twistor space in various Yang-Mills theories. This talk will focus on the MHV diagram approach, which builds in localisation, and will describe work done at Queen Mary which shows how to define MHV diagrams at loop level. This has been successfully applied to give the general one-loop MHV amplitudes in N=4 and N=1 super Yang-Mills.
Posted by: IC
Wed
24 Nov 2004
Yangian and twisted Yangian symmetry in integrable field theory
📍 London
Niall MacKay
(University of York)
Abstract:
We review the role played by the Yangian symmetry generated by non-local charges in a range of integrable models, and in particular the non-linear sigma models, describing briefly the representation theory of the Yangian and its implications for physics. We explain how an integrable boundary naturally reduces this to a 'twisted
Yangian' symmetry.
We review the role played by the Yangian symmetry generated by non-local charges in a range of integrable models, and in particular the non-linear sigma models, describing briefly the representation theory of the Yangian and its implications for physics. We explain how an integrable boundary naturally reduces this to a 'twisted
Yangian' symmetry.
Posted by: KCL
Fri
19 Nov 2004
Unified theories and the increasing synergy between mathematics and physics
📍 London
David Olive
(Swansea)
Abstract:
Annual General Meeting of the London Mathematical Society. See http://www.lms.ac.uk/meetings/AGM04.html for further details.
Annual General Meeting of the London Mathematical Society. See http://www.lms.ac.uk/meetings/AGM04.html for further details.
Posted by: KCL
Fri
19 Nov 2004
Infinite dimensional symmetry
📍 London
Peter Goddard
(IAS)
Abstract:
Annual General Meeting of the London Mathematical Society. See http://www.lms.ac.uk/meetings/AGM04.html for further details.
Annual General Meeting of the London Mathematical Society. See http://www.lms.ac.uk/meetings/AGM04.html for further details.
Posted by: KCL
Thu
18 Nov 2004
A black hole instability as a phase transition in field theory
Sean Hartnoll
(Cambridge)
Abstract:
Generalised black holes have a horizon given by an arbitrary Einstein manifold. I will describe a criterion for the classical stability of these black holes. Roughly, spherical horizons are stable but lemon-shaped horizons can be unstable. In Anti-de Sitter space, these black holes are dual to gauge theory on a curved background given by the same Einstein manifold. I will argue that the dual thermal field theory effect is a novel phase transition induced by inhomogeneous Casimir pressures and characterised by a condensation of pressure.
Generalised black holes have a horizon given by an arbitrary Einstein manifold. I will describe a criterion for the classical stability of these black holes. Roughly, spherical horizons are stable but lemon-shaped horizons can be unstable. In Anti-de Sitter space, these black holes are dual to gauge theory on a curved background given by the same Einstein manifold. I will argue that the dual thermal field theory effect is a novel phase transition induced by inhomogeneous Casimir pressures and characterised by a condensation of pressure.
Posted by: IC
Wed
17 Nov 2004
Exploring the universality class of N=1 SUSY Yang-Mills
Nick Dorey
(DAMTP)
Abstract:
This talk is part of the joint Triangular Seminars
This talk is part of the joint Triangular Seminars
Posted by: KCL
Wed
17 Nov 2004
Mirrors and branes on generalized Calabi-Yau manifolds
Ruben Minasian
(Ecole Polytechnique)
Thu
11 Nov 2004
A Geometry for Non-Geometric String Backgrounds
Chris Hull
(IC)
Thu
11 Nov 2004
Hall algebras and quantum groups: Hopf automorphism groups
Libin Li
(Yangzhou University)
Thu
11 Nov 2004
Black Rings
Jerome P. Gauntlett
(IC)
Wed
10 Nov 2004
GUT spectrum from Heterotic Compactification
📍 London
Yang-Hui He
(University of Pennsylvania)
Thu
4 Nov 2004
TBA
David Seery
(QMW)
Thu
4 Nov 2004
Holographic cubic vertex in the pp-wave
Sangmin Lee
(IC)
Wed
3 Nov 2004
The Bethe ansatz and conformal field theory
📍 London
Werner Nahm
(Dublin Institute for Advanced Studies)
Abstract:
The Bethe ansatz for integrable quantum field theories in two dimensions may well be exact. It can be checked in the conformal limit, where it yields interesting character identities with deep links to algebraic K-theory.
The Bethe ansatz for integrable quantum field theories in two dimensions may well be exact. It can be checked in the conformal limit, where it yields interesting character identities with deep links to algebraic K-theory.
Posted by: KCL
Mon
1 Nov 2004
Towards Quantum Dielectric Branes: Curvature Corrections in Abelian Beta Function and Nonabelian Born-Infeld Action
📍 London
Pedro Bordalo
(King's College)
Abstract:
We compute the beta function at 2 loops for an open string gauge
field F in any (parallelizable) curved background. The beta function is
exact in F. We discuss the implications of this result to curvature
corrections to the Born - Infeld action. Taking the large F limit, we
relate these corrections to the equations of motion for D0-branes in
curved backgrounds, eg. to corrections to the dielectric effect.
We compute the beta function at 2 loops for an open string gauge
field F in any (parallelizable) curved background. The beta function is
exact in F. We discuss the implications of this result to curvature
corrections to the Born - Infeld action. Taking the large F limit, we
relate these corrections to the equations of motion for D0-branes in
curved backgrounds, eg. to corrections to the dielectric effect.
Posted by: KCL
October 2004
Fri
29 Oct 2004
Compact Kahler surfaces of zero scalar curvature
Michael Singer
(Edinburgh)
Fri
29 Oct 2004
Generalized complex geometry and supersymmetry
Maxim Zabzine
(QMW)
Wed
27 Oct 2004
Supersymmetric Black Rings
📍 London
Jan Gutowski
(Oxford University)
Abstract:
The recent discovery of supersymmetric black ring solutions has important implications for black hole uniqueness and other aspects of black hole physics in higher dimensions. The construction of these solutions is investigated, and a generalization of the single ring solution to a system of concentric (multi-charge) rings is presented. The entropy of some of these solutions is particularly interesting.
The recent discovery of supersymmetric black ring solutions has important implications for black hole uniqueness and other aspects of black hole physics in higher dimensions. The construction of these solutions is investigated, and a generalization of the single ring solution to a system of concentric (multi-charge) rings is presented. The entropy of some of these solutions is particularly interesting.
Posted by: KCL
Wed
27 Oct 2004
AdS-CFT beyond supersymmetry via rotating strings
Toni Mateos
(IC)
Abstract:
In the last year and a half, many new tests of the AdS/CFT correspondence have been achieved by studying a certain class of non-topological solitons corresponding to rotating strings which carry (at least) two large angular momenta. They are dual to CFT operators which are far away from the 1/2 BPS operators of Berenstein, Maldacena and Nastase. We will discuss to which point can these results test the AdS/CFT away from supersymmetry.
In the last year and a half, many new tests of the AdS/CFT correspondence have been achieved by studying a certain class of non-topological solitons corresponding to rotating strings which carry (at least) two large angular momenta. They are dual to CFT operators which are far away from the 1/2 BPS operators of Berenstein, Maldacena and Nastase. We will discuss to which point can these results test the AdS/CFT away from supersymmetry.
Posted by: IC
Tue
26 Oct 2004
Projective and injective polynomial modules
Maud De Visscher
(Queen Mary London)
Mon
25 Oct 2004
Correlation functions from spin chains with impurities
Olalla Castro-Alvaredo
(Ecole Normale Superieure de Lyon)
Abstract:
In this talk I will present a short review on the algebraic Bethe ansatz technique and
on the recently found solution of the so-called inverse problem. I will show how this
solution provides a means for the explicit and exact computation of correlation
functions in spin chains and summarize some of the many results obtained in this
direction by members of the theory group at the ENS-Lyon in the last years.
Finally I will present some work still in progress which intends the generalization
of these techniques to the case of spin chains in the presence of impurities.
In this talk I will present a short review on the algebraic Bethe ansatz technique and
on the recently found solution of the so-called inverse problem. I will show how this
solution provides a means for the explicit and exact computation of correlation
functions in spin chains and summarize some of the many results obtained in this
direction by members of the theory group at the ENS-Lyon in the last years.
Finally I will present some work still in progress which intends the generalization
of these techniques to the case of spin chains in the presence of impurities.
Posted by: CityU
Thu
21 Oct 2004
Symmetry and supersymmetry in M-theory backgrounds
Jose' Figueroa-O' Farrill
(Edinburgh)
Wed
20 Oct 2004
Unitarity in the presence of closed timelike curves, and charge quantization
📍 London
Lorenzo Cornalba
(ITFA)
Abstract:
Motivated by string theory arguments, we analyse quantum field theory in
a specific space time with closed timelike curves. We conjecture and
partly show that, for discrete values of the gravitational coupling
constant, the resulting theory is unitary. These discrete values are
obtained in two independent ways, using high energy scattering in quantum
gravity and using string dualities to rephrase the quantization condition
as quantization of charge of certain extended objects.
Motivated by string theory arguments, we analyse quantum field theory in
a specific space time with closed timelike curves. We conjecture and
partly show that, for discrete values of the gravitational coupling
constant, the resulting theory is unitary. These discrete values are
obtained in two independent ways, using high energy scattering in quantum
gravity and using string dualities to rephrase the quantization condition
as quantization of charge of certain extended objects.
Posted by: KCL
Wed
20 Oct 2004
N=1 duality cascades from deformations of N=4 theory
📍 London
Prem Kumar
(DAMTP)
Abstract:
We show that certain exactly marginal and relevant deformations
of N=4 theory which preserve N=1 supersymmetry, exhibit rich infrared
dynamics. These theories have moduli spaces with discrete (Higgs)
branches. On certain branches the theory flows to the Klebanov-Witten
conifold SCFT, while on other branches the theory undergoes a Seiberg
duality cascade terminating in an N=1 theory with a mass gap. Using the
matrix model approach the quantum moduli spaces and quantum
superpotentials of these theories can be computed exactly. In the D-brane
picture these quantum moduli spaces correspond to the Calabi-Yau space in
the geometric dual description of the gauge theory.
We show that certain exactly marginal and relevant deformations
of N=4 theory which preserve N=1 supersymmetry, exhibit rich infrared
dynamics. These theories have moduli spaces with discrete (Higgs)
branches. On certain branches the theory flows to the Klebanov-Witten
conifold SCFT, while on other branches the theory undergoes a Seiberg
duality cascade terminating in an N=1 theory with a mass gap. Using the
matrix model approach the quantum moduli spaces and quantum
superpotentials of these theories can be computed exactly. In the D-brane
picture these quantum moduli spaces correspond to the Calabi-Yau space in
the geometric dual description of the gauge theory.
Posted by: KCL
Thu
14 Oct 2004
Semiclassicalisation of quantum differentials and nonassociative quantization
Shahn Majid
(QMW)
Thu
14 Oct 2004
Vortices, Strings and Vortex Strings
David Tong
(Cambridge)
Abstract:
I will summarise recent progress in understanding the dynamics of vortices in gauge theories and describe how the vortices can be used as probes to extract information about the strong coupling quantum dynamics of the theory in which its embedded.
I will summarise recent progress in understanding the dynamics of vortices in gauge theories and describe how the vortices can be used as probes to extract information about the strong coupling quantum dynamics of the theory in which its embedded.
Posted by: IC
Wed
13 Oct 2004
Gauged Maximal Supergravities and their Domain Walls
📍 London
Diederik Roest
(KCL)
Wed
13 Oct 2004
An M - theory model of a Big Crunch Big Bang transition
Neil Turok
(DAMTP)
Mon
11 Oct 2004
Towards Gauge theory for commutative, non-associative algebras
Sanjaye Ramgoolam
(QMW)
Thu
7 Oct 2004
Self-dual strings and anomalies
David Berman
(QMW)
Thu
7 Oct 2004
tba
Michela Petrini
(Ecole Polytechnique de Paris and Universite de Tours)
September 2004
Thu
30 Sep 2004
Topological conformal field theories from Calabi-Yau categories
Kevin Costello
(IC)
Abstract:
This is part of the London topology and geometry seminars
This is part of the London topology and geometry seminars
Posted by: KCL
Thu
30 Sep 2004
tba
Annamaria Sinkovics
(University of Amsterdam)
Tue
28 Sep 2004
Multi-leg loop amplitudes in N=4 super-Yang-Mills theory
Lance Dixon
(SLAC and Durham IPPP)
Mon
27 Sep 2004
Graded Riemann Spheres and two dimensional Conformal Field Theory
📍 London
Jasbir Nagi
(DAMTP, Cambridge)
Abstract:
Riemann Spheres are extremely useful as objects to build Conformal
Field Theory on. Graded Riemann Spheres turn out to be extremely
useful in the study Superconformal Field Theory. In particular, I will
look at the conformal algebras of vector fields that arise, and their
associated primary fields that are given by the geometry. I will also look
at some peculiarities that arise in N=4 theories.
Riemann Spheres are extremely useful as objects to build Conformal
Field Theory on. Graded Riemann Spheres turn out to be extremely
useful in the study Superconformal Field Theory. In particular, I will
look at the conformal algebras of vector fields that arise, and their
associated primary fields that are given by the geometry. I will also look
at some peculiarities that arise in N=4 theories.
Posted by: KCL
Fri
24 Sep 2004
Higher-loop scattering amplitudes in N=4 super-Yang-Mills theory
Lance Dixon
(SLAC)
Thu
23 Sep 2004
WZW branes by quantum algebras
Jacek Pawelczyk
(Warsaw University)
Thu
23 Sep 2004
Supertwistorial N=2 String Field Theory
Olaf Lechtenfeld
(University of Hannover)