Triangle Seminars
December 2006
Wed
13 Dec 2006
Sightseeing in the Landscape
Bert Schellekens
(NIKHEF)
Wed
13 Dec 2006
Metastable Vacua, Geometric Engineering and MQCD Transition
Radu Tatar
(Liverpool)
Mon
11 Dec 2006
Holonomy in higher dimensions - Lie theory for differential graded Lie algebras
Ezra Getzler
Fri
8 Dec 2006
Higher-order corrections in string and M-theory, and generalised holonomy
Chris Pope
(Texas A M University)
Thu
7 Dec 2006
Open/closed string correspondence and D-brane decay in curved space
📍 London
Marco Baumgartl
(ETH Zuerich)
Abstract:
Boundary string field theory is an open string field theory which has been originally formulated on a flat target space. In this talk I present recent progress in the study of BSFT in curved space backgrounds. Starting from a factorization property of the associated path-integral, non-local open string couplings can be identified which implement shifts in the closed string background. This generally affects the stability of D-branes, which is analyzed with renormalisation group methods. Evidence for the conjectured flow towards D-branes in curved space is presented for the example of a SU(2) WZW model.
Boundary string field theory is an open string field theory which has been originally formulated on a flat target space. In this talk I present recent progress in the study of BSFT in curved space backgrounds. Starting from a factorization property of the associated path-integral, non-local open string couplings can be identified which implement shifts in the closed string background. This generally affects the stability of D-branes, which is analyzed with renormalisation group methods. Evidence for the conjectured flow towards D-branes in curved space is presented for the example of a SU(2) WZW model.
Posted by: KCL
Thu
7 Dec 2006
Kahler Potentials for Chiral Matter in Calabi-Yau String
Joe Conlon
(DAMPT, Cambridge)
Abstract:
The Kahler metric for chiral matter fields plays a crucial role in the
computation of soft supersymmetry breaking terms in string
compactifications. Due to its non-holomorphic nature, this is difficult to
compute in Calabi-Yau backgrounds. I describe techniques that allow the
modular weights of the Kahler metric to be computed in IIB string
compactifications. This is done by relating the modular dependence
of the Kahler metric to that of the physical Yukawa couplings. I briefly
discuss the applications to soft terms and neutrino masses.
The Kahler metric for chiral matter fields plays a crucial role in the
computation of soft supersymmetry breaking terms in string
compactifications. Due to its non-holomorphic nature, this is difficult to
compute in Calabi-Yau backgrounds. I describe techniques that allow the
modular weights of the Kahler metric to be computed in IIB string
compactifications. This is done by relating the modular dependence
of the Kahler metric to that of the physical Yukawa couplings. I briefly
discuss the applications to soft terms and neutrino masses.
Posted by: IC
Thu
7 Dec 2006
Boundary Conformal Field Theory and Ribbon Graphs: A Tool for Open/Closed String Dualities
Valeria Gili
(QMUL)
Wed
6 Dec 2006
Solitons in ferromagnets
📍 London
Paul Sutcliffe
(Durham University)
Abstract:
I shall discuss various solitons which are possible in a ferromagnetic medium. Examples include domain walls, magnetic bubbles, vortex rings and Hopf solitons.
I shall discuss various solitons which are possible in a ferromagnetic medium. Examples include domain walls, magnetic bubbles, vortex rings and Hopf solitons.
Posted by: KCL
Wed
6 Dec 2006
Quantum many-body systems: Simulation, entanglement, and complexity. A quantum information perspective
Jens Eisert
(Imperial College London)
Tue
5 Dec 2006
Towards Black Rings in AdS
Chethan Gowdigere
(ICTP, Trieste)
November 2006
Thu
30 Nov 2006
Thermodynamics at the BPS bound for Black Holes in AdS
Pedro J. Silva
Abstract:
In this work we define a new limiting procedure that extends the usual thermodynamics treatment of Black Hole physics, to the supersymmetric regime. This procedure is inspired on equivalent statistical mechanics derivations in the dual CFT theory, where the BPS partition function at zero temperature is obtained by a double scaling limit of temperature and the relevant chemical potentials. In supergravity, the resulting partition function depends on emergent generalized chemical potentials conjugated to the different conserved charges of the BPS solitons. With this new approach, studies on stability and phase transitions of supersymmetric solutions are presented. We find stable and unstable regimes with first order phase transitions, as suggested by previous studies on free supersymmetric Yang Mills theory.
In this work we define a new limiting procedure that extends the usual thermodynamics treatment of Black Hole physics, to the supersymmetric regime. This procedure is inspired on equivalent statistical mechanics derivations in the dual CFT theory, where the BPS partition function at zero temperature is obtained by a double scaling limit of temperature and the relevant chemical potentials. In supergravity, the resulting partition function depends on emergent generalized chemical potentials conjugated to the different conserved charges of the BPS solitons. With this new approach, studies on stability and phase transitions of supersymmetric solutions are presented. We find stable and unstable regimes with first order phase transitions, as suggested by previous studies on free supersymmetric Yang Mills theory.
Posted by: IC
Thu
30 Nov 2006
Heterotic M-theory simplified
Ian Moss
(Newcastle)
Abstract:
The theory of supergravity on manifolds with boundary leads to very tightly
constrained boundary conditions. When applied to low energy heterotic M
theory, these boundary conditions are inconsistent with the work of Horava
and Witten, but lead to a simplification of their action. The reduction of
the new theory throws up some interesting new insights into gaugino
condensation and no-scale supergravity models. The new theory also suggests
the existence of a new type of index theorem.
The theory of supergravity on manifolds with boundary leads to very tightly
constrained boundary conditions. When applied to low energy heterotic M
theory, these boundary conditions are inconsistent with the work of Horava
and Witten, but lead to a simplification of their action. The reduction of
the new theory throws up some interesting new insights into gaugino
condensation and no-scale supergravity models. The new theory also suggests
the existence of a new type of index theorem.
Posted by: QMW
Wed
29 Nov 2006
Integrability and the AdS/CFT correspondence at large R-charge
📍 London
Nick Dorey
(DAMTP, Cambridge)
Wed
29 Nov 2006
A geometric description of m-cluster categories
Karin Baur
(University of Leicester)
Abstract:
This is joint work with R. Marsh (Leeds).
I will describe m-cluster categories of type A
using a category of diagonals of a regular polygon.
This generalises a result of Caldero, Chapoton and
Schiffler for m=1.
This is joint work with R. Marsh (Leeds).
I will describe m-cluster categories of type A
using a category of diagonals of a regular polygon.
This generalises a result of Caldero, Chapoton and
Schiffler for m=1.
Posted by: CityU
Mon
27 Nov 2006
Integrability in gauge theory and string theory VI
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Thu
23 Nov 2006
Compactifications on Hyperbolic Spaces
Domenico Orlando
(University degli Studi di Milano Bicocca)
Abstract:
Negative curvature Euclidean (Hyperbolic) spaces have already been used in literature as part of eleven dimensional supergravity solutions. In particular it has been shown that they naturally appear when building expanding cosmological models. In this talk I will present M-theory solutions written as direct products of maximally symmetric spaces with hyperbolic components. These backgrounds break supersymmetry because of global effects but are still stable with respect to small scalar perturbations. They appear as near-horizon geometries for wrapped M5-branes, thus allowing for an intuitive interpretation of their stability.
Negative curvature Euclidean (Hyperbolic) spaces have already been used in literature as part of eleven dimensional supergravity solutions. In particular it has been shown that they naturally appear when building expanding cosmological models. In this talk I will present M-theory solutions written as direct products of maximally symmetric spaces with hyperbolic components. These backgrounds break supersymmetry because of global effects but are still stable with respect to small scalar perturbations. They appear as near-horizon geometries for wrapped M5-branes, thus allowing for an intuitive interpretation of their stability.
Posted by: IC
Thu
23 Nov 2006
Wilson Loop Correlators and D-Branes from Matrix Models
Riccardo Ricci
(Imperial)
Wed
22 Nov 2006
Have modified branes got us spooked?
📍 London
Ruth Gregory
(Durham University)
Wed
22 Nov 2006
The non-Hermitian Floquet theory of multiphoton processes in strong laser fields: Plateau resonances and the quasienergy spectrum of argon
Robert Potvliege
(University of Durham)
Abstract:
An atom exposed to an intense laser field may loose one or several of its electrons by photoionization. The field effectively turns all bound states into resonances of finite lifetime. For fields of constant intensity, this process is amenable to a time-independent description based on the method of complex scaling and on the Floquet theory of differential equations with periodic coefficients. The ionization rate of the state and the position of multiphoton resonances between Stark-shifted states can then be inferred from the spectrum of complex quasienergies of the Hamiltonian. After a general introduction to this approach, the talk will concentrate on a recent study of the origin of the sharp enhancements of emission of fast photoelectrons at certain intensities found a few years ago in the ionization of rare gases.
An atom exposed to an intense laser field may loose one or several of its electrons by photoionization. The field effectively turns all bound states into resonances of finite lifetime. For fields of constant intensity, this process is amenable to a time-independent description based on the method of complex scaling and on the Floquet theory of differential equations with periodic coefficients. The ionization rate of the state and the position of multiphoton resonances between Stark-shifted states can then be inferred from the spectrum of complex quasienergies of the Hamiltonian. After a general introduction to this approach, the talk will concentrate on a recent study of the origin of the sharp enhancements of emission of fast photoelectrons at certain intensities found a few years ago in the ionization of rare gases.
Posted by: CityU
Mon
20 Nov 2006
Integrability in gauge theory and string theory V
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Thu
16 Nov 2006
Magnon Boundstates in Gauge/String Duality
Heng-Yu Chen
(DAMTP, Cambridge)
Abstract:
I will begin with basic review on the integrabilities in AdS/CFT correspondence, and move on discussing the role of scattering matrices in gauge and string thoeries. I will then explain the formation of magnon boundststates in gauge theory and their corresponding classical string solution. The scattering of magnon boundstates and their classifications will also be discussed in this seminar. I will also mention some work in progress.
I will begin with basic review on the integrabilities in AdS/CFT correspondence, and move on discussing the role of scattering matrices in gauge and string thoeries. I will then explain the formation of magnon boundststates in gauge theory and their corresponding classical string solution. The scattering of magnon boundstates and their classifications will also be discussed in this seminar. I will also mention some work in progress.
Posted by: IC
Wed
15 Nov 2006
Faster than Hermitian Quantum Mechanics?
Dorje Brody
(Imperial College London)
Abstract:
Given an initial quantum state and a final quantum state in a Hilbert space, there exist Hamiltonians H that transform one into the other. Subject to the constraint that the difference between the largest and smallest eigenvalues of H is held fixed, which H achieves this transformation in the least time? For Hermitian Hamiltonians this time has a nonzero lower bound. However, among complex PT-symmetric Hamiltonians satisfying the same energy constraint, this time can be made arbitrarily small without violating the time-energy uncertainty principle. The talk will discuss the possible implications of this result.
Given an initial quantum state and a final quantum state in a Hilbert space, there exist Hamiltonians H that transform one into the other. Subject to the constraint that the difference between the largest and smallest eigenvalues of H is held fixed, which H achieves this transformation in the least time? For Hermitian Hamiltonians this time has a nonzero lower bound. However, among complex PT-symmetric Hamiltonians satisfying the same energy constraint, this time can be made arbitrarily small without violating the time-energy uncertainty principle. The talk will discuss the possible implications of this result.
Posted by: CityU
Wed
15 Nov 2006
Higgs Bundles, Gauge Theories and Quantum Groups
📍 London
Samson L. Shatashvili
(Hamilton Mathematics Institute, Trinity, Dublin)
Abstract:
(check the triangle webpage under menu 'triangle' for directions to the seminar room)
(check the triangle webpage under menu 'triangle' for directions to the seminar room)
Posted by: KCL
Wed
15 Nov 2006
Matching the Hagedorn temperature in AdS/CFT
📍 London
Troels Harmark
(Niels Bohr Institute)
Mon
13 Nov 2006
Integrability in gauge theory and string theory IV
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Wed
8 Nov 2006
Ultra-violet finiteness of planar beta-deformed Yang-Mills
📍 London
Stefano Kovacs
(Trinity College, Dublin)
Wed
8 Nov 2006
Dilatation operator for N=4 SYM vs giant gravitons and open strings
Guillermo Silva
(Universidad Nacional de La Plata)
Abstract:
We will discuss the one-loop anomalous dimensions of Super Yang-Mills operators dual to open strings ending on AdS giant gravitons (AGG) and describe the spin chain description of gauge theory operators. A semi-classical analysis of the Hamiltonian describing the anomalous dimensions of AGG operators will allow us to give a geometrical (stringy) interpretation for the gauge theory parameters. This same analysis will also show evidence for the existence of continuous bands in the Hamiltonian spectrum.
We will discuss the one-loop anomalous dimensions of Super Yang-Mills operators dual to open strings ending on AdS giant gravitons (AGG) and describe the spin chain description of gauge theory operators. A semi-classical analysis of the Hamiltonian describing the anomalous dimensions of AGG operators will allow us to give a geometrical (stringy) interpretation for the gauge theory parameters. This same analysis will also show evidence for the existence of continuous bands in the Hamiltonian spectrum.
Posted by: IC
Wed
8 Nov 2006
The Solomon descent algebra
Manfred Schocker
(University of Swansea)
Abstract:
Please check the local City seminar website for abstract.
Please check the local City seminar website for abstract.
Posted by: CityU
Mon
6 Nov 2006
Integrability in gauge theory and string theory III
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Thu
2 Nov 2006
Describing curved spaces by matrices
Yusuke Kimura
(QMUL)
Wed
1 Nov 2006
Free and interacting higher spin fields on AdS(d)
📍 London
Mirian Tsulaia
(University of Crete)
Wed
1 Nov 2006
Electromagnetic duality and the Langlands programme
David Olive
(University of Swansea)
Abstract:
A recent paper by Kapustin and Witten synthesises ideas from
pure mathematics and quantum field theory that have been developing independently for more than thirty years. Thus the Langlands programme, itself a unification scheme in mathematics, relates to electromagnetic duality and
the topological twisting of supersymmetry. An attempt will be made to explain these ideas.
A recent paper by Kapustin and Witten synthesises ideas from
pure mathematics and quantum field theory that have been developing independently for more than thirty years. Thus the Langlands programme, itself a unification scheme in mathematics, relates to electromagnetic duality and
the topological twisting of supersymmetry. An attempt will be made to explain these ideas.
Posted by: CityU
October 2006
Mon
30 Oct 2006
Integrability in gauge theory and string theory II
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Thu
26 Oct 2006
Pure Spinor Strings and Non-Critical Strings
Pietro Antonio Grassi
(Alessandria (Univ. Piemonte Orientale))
Wed
25 Oct 2006
Geometry and Duality: T-folds and Non-Geometric Backgrounds in String Theory
📍 London
Christopher Hull
(Imperial College London)
Wed
25 Oct 2006
When cooler is not better: Stochastic Resonance Phenomena in Quantum Many-Body Systems
Susana Huelga
(University of Hertfordshire)
Abstract:
The presence of noise is normally associated with a decrease in the optimal performance of any detection or information processing scheme. However, this is not always the case, as illustrated by the phenomenon of stochastic resonance where the response of a non-linear system displays a resonant-like dependence on the noise strength.
I will discuss stochastic resonance (SR) effects in weakly driven coupled quantum systems. I will show that both dynamical and information theoretic measures of the system's response can be introduced that exhibit a non-monotonic behaviour as a function of the noise strength. The relation between lack of monotonicity in the response and the presence of quantum correlations will be analyzed, showing that there are parameter regimes where the breakdown of a linear response can be associated to the presence of entanglement. I will also argue that a chain of coupled spin systems can exhibit a form of array-enhanced response, where the sensitivity of a single resonator to a weak driving signal is enhanced as a result of the nearest-neighbour coupling. These results enlarge the domain where SR effects exist and should be observable in state-of-the-art arrays of superconducting qubits.
The presence of noise is normally associated with a decrease in the optimal performance of any detection or information processing scheme. However, this is not always the case, as illustrated by the phenomenon of stochastic resonance where the response of a non-linear system displays a resonant-like dependence on the noise strength.
I will discuss stochastic resonance (SR) effects in weakly driven coupled quantum systems. I will show that both dynamical and information theoretic measures of the system's response can be introduced that exhibit a non-monotonic behaviour as a function of the noise strength. The relation between lack of monotonicity in the response and the presence of quantum correlations will be analyzed, showing that there are parameter regimes where the breakdown of a linear response can be associated to the presence of entanglement. I will also argue that a chain of coupled spin systems can exhibit a form of array-enhanced response, where the sensitivity of a single resonator to a weak driving signal is enhanced as a result of the nearest-neighbour coupling. These results enlarge the domain where SR effects exist and should be observable in state-of-the-art arrays of superconducting qubits.
Posted by: CityU
Mon
23 Oct 2006
Integrability in gauge theory and string theory I
Nick Dorey
(Cambridge/Imperial Maths Institute)
Abstract:
This the first of a series of lectures in which I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
This the first of a series of lectures in which I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.
Posted by: IC
Wed
18 Oct 2006
IIB brane actions and SL(2,R)
📍 London
Fabio Riccioni
(King's College London)
Abstract:
Ten-dimensional IIB supergravity is invariant under the symmetry group
SL(2.R). We give a classification of all the forms that are present in the
IIB supersymmetry algebra as representations of SL(2,R),
and we show under
which conditions these forms are associated to branes
whose effective actions are kappa symmetric. We use these results to give a simple universal
SL(2,R)-invariant expression for all IIB brane actions.
Ten-dimensional IIB supergravity is invariant under the symmetry group
SL(2.R). We give a classification of all the forms that are present in the
IIB supersymmetry algebra as representations of SL(2,R),
and we show under
which conditions these forms are associated to branes
whose effective actions are kappa symmetric. We use these results to give a simple universal
SL(2,R)-invariant expression for all IIB brane actions.
Posted by: KCL
Wed
18 Oct 2006
Phase Structure of N=4 SYM and Gravity in Anti-de Sitter Space
Asad Naqvi
(Swansea)
Wed
18 Oct 2006
Schensted correspondence and Littelmann paths
Karin Erdmann
(Oxford University)
Abstract:
This is joint work with J.A. Green and M. Schocker. We study the Littelmann path model for the case gln. In this case, Littelmann's paths become words, and we work with the combinatorics of words. This leads to the representation theory of the Littelmann algebra which is a close analogue of the Schur algebra.
This is joint work with J.A. Green and M. Schocker. We study the Littelmann path model for the case gln. In this case, Littelmann's paths become words, and we work with the combinatorics of words. This leads to the representation theory of the Littelmann algebra which is a close analogue of the Schur algebra.
Posted by: CityU
Tue
17 Oct 2006
Statistical Physics Approach to Models of Risk
Reimer Kuehn
(KCL)
Abstract:
We look at the problem of estimating risk (Operational Risk, Credit Risk and Market Risk) and argue that risk elements, such as processes in an organization, credits in a loan-portfolio or share prices in an investment portfolio cannot be regarded as independent. This naturally leads to formulating risk models as dynamical models of interacting degrees of freedom (particles). The operational risk and
credit risk problems can be cast into a language describing heterogeneous lattice gasses, in which interaction parameters and non-uniform chemical potentials have an interpretation in terms of unconditional and conditional failure probabilities. For the market risk problem, a minimal interacting generalization of the classical Geometric Brownian Motion model leads to a formulation of market
dynamics that is formally similar to the dynamics of graded response neurons. We describe elements of the statistical mechanical analysis of these models to reveal their macroscopic properties.
We look at the problem of estimating risk (Operational Risk, Credit Risk and Market Risk) and argue that risk elements, such as processes in an organization, credits in a loan-portfolio or share prices in an investment portfolio cannot be regarded as independent. This naturally leads to formulating risk models as dynamical models of interacting degrees of freedom (particles). The operational risk and
credit risk problems can be cast into a language describing heterogeneous lattice gasses, in which interaction parameters and non-uniform chemical potentials have an interpretation in terms of unconditional and conditional failure probabilities. For the market risk problem, a minimal interacting generalization of the classical Geometric Brownian Motion model leads to a formulation of market
dynamics that is formally similar to the dynamics of graded response neurons. We describe elements of the statistical mechanical analysis of these models to reveal their macroscopic properties.
Posted by: brunel
Fri
13 Oct 2006
Probabilities in eternal inflation
Raphael Bousso
(UC, Berkeley and LBL, Berkeley)
Thu
12 Oct 2006
N=4 Superconformal Characters and Partition Functions
Paul Heslop
(QMUL)
Wed
11 Oct 2006
Conformal Holography and an AdS Instanton
📍 London
Sebastian de Haro
(King's College London)
Abstract:
I will discuss an instanton solution preserving AdS boundary conditions.
It arises in a compactification of M-theory to four dimensions, keeping a
single scalar coupled to gravity with a phi to the 4th potential. We study the
holography of this solution in the context of a toy model, where the
effective boundary CFT is a conformally coupled scalar with a phi to the 6th
potential in three dimensions. We match bulk and boundary instanton
solutions as well as fluctuations around them. Using a form of radial
quantization we show that quantum states in the bulk correspond to
multiply-occupied single particle states in the boundary theory. I will
discuss the interpretation of the instanton in the dual CFT as a deformation
by a triple-trace operator, and how the instanton signals an instability
of the theory under this deformation.
I will discuss an instanton solution preserving AdS boundary conditions.
It arises in a compactification of M-theory to four dimensions, keeping a
single scalar coupled to gravity with a phi to the 4th potential. We study the
holography of this solution in the context of a toy model, where the
effective boundary CFT is a conformally coupled scalar with a phi to the 6th
potential in three dimensions. We match bulk and boundary instanton
solutions as well as fluctuations around them. Using a form of radial
quantization we show that quantum states in the bulk correspond to
multiply-occupied single particle states in the boundary theory. I will
discuss the interpretation of the instanton in the dual CFT as a deformation
by a triple-trace operator, and how the instanton signals an instability
of the theory under this deformation.
Posted by: KCL
Wed
11 Oct 2006
Spectral equivalences from bosonic Hamiltonians
Clare Dunning
(University of Kent)
Abstract:
We discuss two integrable Hamiltonians describing the physics of interconversion of bosonic atoms and di-atomic molecules. By mapping the energy spectrums of these models onto a pair of Schrodinger equations we are able to establish a spectral equivalence between a Hermitian Schrodinger problem and a PT-symmetric Schrodinger equation.
We discuss two integrable Hamiltonians describing the physics of interconversion of bosonic atoms and di-atomic molecules. By mapping the energy spectrums of these models onto a pair of Schrodinger equations we are able to establish a spectral equivalence between a Hermitian Schrodinger problem and a PT-symmetric Schrodinger equation.
Posted by: CityU
Wed
4 Oct 2006
Counting BPS states
📍 London
Bo Feng
(Imperial College, London)
Abstract:
We develop a systematic and efficient method of counting single-trace and multi-trace BPS operators with two supercharges, for world-volume gauge theories of N D-brane probes for both large and finite N. The techniques are applicable to generic singularities, orbifold, toric, non-toric, complete intersections, et cetera, even to geometries whose precise field theory duals are not yet known. The so-called Plethystic Exponential provides a simple bridge between the defining equation of the Calabi-Yau, the generating function of single-trace BPS operators and the generating function of multi-trace operators. Mathematically, fascinating and intricate inter-relations between gauge theory, algebraic geometry, combinatorics and number theory exhibit themselves in the form of plethystics and syzygies.
We develop a systematic and efficient method of counting single-trace and multi-trace BPS operators with two supercharges, for world-volume gauge theories of N D-brane probes for both large and finite N. The techniques are applicable to generic singularities, orbifold, toric, non-toric, complete intersections, et cetera, even to geometries whose precise field theory duals are not yet known. The so-called Plethystic Exponential provides a simple bridge between the defining equation of the Calabi-Yau, the generating function of single-trace BPS operators and the generating function of multi-trace operators. Mathematically, fascinating and intricate inter-relations between gauge theory, algebraic geometry, combinatorics and number theory exhibit themselves in the form of plethystics and syzygies.
Posted by: KCL
Wed
4 Oct 2006
Solving Painleve' connection problems using 2-dimensional integrable quantum field theory
Benjamin Doyon
(Oxford University)
Abstract:
TBA
TBA
Posted by: CityU
Tue
3 Oct 2006
Twistor Strings and Gravity
Mohab Abou-Zeid
(Vrije U., Brussels and Intl. Solvay Inst., Brussels)
Abstract:
I will present a modification of the Berkovits twistor string model which gives Einstein supergravity coupled to Yang-Mills, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes. I will start by reviewing a number of relevant aspects of twistor theory, including special features associated with different space-time signatures, supertwistor space, the Penrose transform, the infinity twistor and Penrose's non-linear graviton construction. I will then review the Witten and Berkovits twistor strings, with emphasis on the latter. The world-sheet formulation of the Berkovits model involves so-called beta-gamma systems, I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from world-sheet anomalies. I will also describe the corresponding spectra in space-time, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N = 8 supergravity, two theories with the spectrum of N = 4 supergravity coupled to N = 4 Yang-Mills, a family of N greater than 0 models with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills, and a non-supersymmetric string with the spectrum of self-dual gravity coupled to self-dual Yang-Mills and a scalar. Time permitting, I will discuss what is known about the interactions.
I will present a modification of the Berkovits twistor string model which gives Einstein supergravity coupled to Yang-Mills, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes. I will start by reviewing a number of relevant aspects of twistor theory, including special features associated with different space-time signatures, supertwistor space, the Penrose transform, the infinity twistor and Penrose's non-linear graviton construction. I will then review the Witten and Berkovits twistor strings, with emphasis on the latter. The world-sheet formulation of the Berkovits model involves so-called beta-gamma systems, I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from world-sheet anomalies. I will also describe the corresponding spectra in space-time, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N = 8 supergravity, two theories with the spectrum of N = 4 supergravity coupled to N = 4 Yang-Mills, a family of N greater than 0 models with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills, and a non-supersymmetric string with the spectrum of self-dual gravity coupled to self-dual Yang-Mills and a scalar. Time permitting, I will discuss what is known about the interactions.
Posted by: IC
Tue
3 Oct 2006
Spectrum of the Dirac operator in the Schwinger model
Leonid Shifrin
(Brunel)
Abstract:
Chiral symmetry and its spontaneous breaking (ChSB ) play a major role in the low-energy dynamics of Quantum Chromodynamics (QCD). In the language of Dirac eigenvalues, ChSB imposes strong constraints on Dirac spectra, called Leutwyler-Smilga (LS) spectral sum rules. These sum rules were originally derived for QCD on rather general grounds.
I will give an alternative simple combinatorial derivation of the LS sum rules for 1 flavor, based on cluster property and chiral decomposition. Further, I will sketch the exact microscopic (field theory) derivation of them in the closely related to QCD but much simpler 2-dimensional Schwinger model. I will also discuss several related topics including breaking of cluster property in multi-flavor QCD, Random Matrix Theory calculation of the leading mass dependence of the QCD partition function, and the so-called spectral duality.
Chiral symmetry and its spontaneous breaking (ChSB ) play a major role in the low-energy dynamics of Quantum Chromodynamics (QCD). In the language of Dirac eigenvalues, ChSB imposes strong constraints on Dirac spectra, called Leutwyler-Smilga (LS) spectral sum rules. These sum rules were originally derived for QCD on rather general grounds.
I will give an alternative simple combinatorial derivation of the LS sum rules for 1 flavor, based on cluster property and chiral decomposition. Further, I will sketch the exact microscopic (field theory) derivation of them in the closely related to QCD but much simpler 2-dimensional Schwinger model. I will also discuss several related topics including breaking of cluster property in multi-flavor QCD, Random Matrix Theory calculation of the leading mass dependence of the QCD partition function, and the so-called spectral duality.
Posted by: brunel
Mon
2 Oct 2006
Twistor Strings and Gravity
Mohab Abou Zeid
(Vrije U., Brussels and Intl. Solvay Inst., Brussels)
Abstract:
I will present a modification of the Berkovits twistor string model which gives Einstein supergravity coupled to Yang-Mills, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes. I will start by reviewing a number of relevant aspects of twistor theory, including special features associated with different space-time signatures, supertwistor space, the Penrose transform, the infinity twistor and Penrose's non-linear graviton construction. I will then review the Witten and Berkovits twistor strings, with emphasis on the latter. The world-sheet formulation of the Berkovits model involves so-called beta-gamma systems, I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from world-sheet anomalies. I will also describe the corresponding spectra in space-time, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N = 8 supergravity, two theories with the spectrum of N = 4 supergravity coupled to N = 4 Yang-Mills, a family of N greater than 0 models with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills, and a non-supersymmetric string with the spectrum of self-dual gravity coupled to self-dual Yang-Mills and a scalar. Time permitting, I will discuss what is known about the interactions.
I will present a modification of the Berkovits twistor string model which gives Einstein supergravity coupled to Yang-Mills, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes. I will start by reviewing a number of relevant aspects of twistor theory, including special features associated with different space-time signatures, supertwistor space, the Penrose transform, the infinity twistor and Penrose's non-linear graviton construction. I will then review the Witten and Berkovits twistor strings, with emphasis on the latter. The world-sheet formulation of the Berkovits model involves so-called beta-gamma systems, I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from world-sheet anomalies. I will also describe the corresponding spectra in space-time, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N = 8 supergravity, two theories with the spectrum of N = 4 supergravity coupled to N = 4 Yang-Mills, a family of N greater than 0 models with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills, and a non-supersymmetric string with the spectrum of self-dual gravity coupled to self-dual Yang-Mills and a scalar. Time permitting, I will discuss what is known about the interactions.
Posted by: IC
September 2006
Tue
19 Sep 2006
Semiclassical Theory for Parametric Correlation of Energy Levels
Taro Nagao
(Nagoya University)
Abstract:
Using semiclassical periodic orbit theory for a chaotic system, we evaluated the energy level correlation depending on the magnetic field as an external parameter. The result is in agreement with the prediction of parameter-dependent random matrix theory.
Using semiclassical periodic orbit theory for a chaotic system, we evaluated the energy level correlation depending on the magnetic field as an external parameter. The result is in agreement with the prediction of parameter-dependent random matrix theory.
Posted by: brunel