Triangle Seminars
July 2005
Mon
18 Jul 2005
Knizhnik-Zamolodchikov equations and spectral flow in AdS3 string theory
📍 London
Sylvain Ribault
(King's College London)
Abstract:
KZ equations are an essential tool in the study of conformal
field theories with affine algebra symmetry. They are satisfied by all
correlation functions of affine primary fields. However, string theory in
AdS3 forces us to consider fields which are not affine primaries. I will
explain that some generalizations of the KZ equations nevertheless still
hold. I will discuss the implications of this finding for the relation
with Liouville theory and the operator product expansion in the H3 model.
KZ equations are an essential tool in the study of conformal
field theories with affine algebra symmetry. They are satisfied by all
correlation functions of affine primary fields. However, string theory in
AdS3 forces us to consider fields which are not affine primaries. I will
explain that some generalizations of the KZ equations nevertheless still
hold. I will discuss the implications of this finding for the relation
with Liouville theory and the operator product expansion in the H3 model.
Posted by: KCL
Wed
6 Jul 2005
Affine Toda field theories related to Coxeter groups of non-crystallographic type
📍 London
Andreas Fring
(City University)
Abstract:
We propose affine Toda field theories related to the non-crystallographic
Coxeter groups H_2, H_3 and H_4. The classical mass spectrum, the classical
three-point couplings and the one-loop corrections to the mass renormalisation
are determined. The construction is carried out by means of a reduction
procedure from crystallographic to non-crystallographic Coxeter groups. The
embedding structure explains for various affine Toda field theories that their
particles can be organised in pairs, such that their relative masses differ by
the golden ratio.
We propose affine Toda field theories related to the non-crystallographic
Coxeter groups H_2, H_3 and H_4. The classical mass spectrum, the classical
three-point couplings and the one-loop corrections to the mass renormalisation
are determined. The construction is carried out by means of a reduction
procedure from crystallographic to non-crystallographic Coxeter groups. The
embedding structure explains for various affine Toda field theories that their
particles can be organised in pairs, such that their relative masses differ by
the golden ratio.
Posted by: KCL
Fri
1 Jul 2005
Rotating Black Holes and Einstein-Sasaki Spaces
Chris Pope
(Texas A&M)
June 2005
Thu
30 Jun 2005
Statistics of M theory Vacua and the Landscape
Bobby Acharya
(ICTP Trieste)
Wed
29 Jun 2005
Topological String Theory III
Cumrun Vafa
(Harvard University)
Tue
28 Jun 2005
Topological String Theory II
Cumrun Vafa
(Harvard University)
Mon
27 Jun 2005
Topological String Theory I
Cumrun Vafa
(Harvard University)
Fri
24 Jun 2005
Generalized geometry and physics III
Marco Gualtieri
(Fields Institute)
Abstract:
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Posted by: KCL
Thu
23 Jun 2005
SEMINAR CANCELLED
Pierre Vanhove
(Saclay)
Wed
22 Jun 2005
Generalized geometry and physics II
Marco Gualtieri
(Fields Institute)
Abstract:
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Posted by: IC
Mon
20 Jun 2005
Generalized geometry and physics I
Marco Gualtieri
(Fields Institute)
Abstract:
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Generalized complex geometry is a unification of complex and symplectic geometry, and provides a geometrical context for understanding parts of mirror symmetry. In these lectures I will provide an introduction to generalized complex, Kahler, and related geometries, and describe some of their appearances in physics.
Posted by: IC
Fri
17 Jun 2005
Self-dual metrics with Killing fields and complex geometry
Simon Donaldson
(IC)
Thu
16 Jun 2005
Towards a Perfect QCD Gravity Dual
Nick Evans
(Southhampton)
Abstract:
TBA
TBA
Posted by: IC
Tue
14 Jun 2005
Latest results from Cassini
Michele Dougherty
(Imperial College)
Mon
13 Jun 2005
Introduction to Toric Geometry
Richard Thomas
(Imperial College)
Thu
9 Jun 2005
Nonperturbative effects in the BMN limit
Aninda Sinha
(Cambridge)
Thu
9 Jun 2005
Noncentral extension of AdS superalgebra
Jeong-Hyuck Park
(IHES-Paris)
Abstract:
Four dimensional N=4 super Yang-Mills theory contains a bigger superalgebra than AdS or superconformal algebra, su(2,2/4). It corresponds to a noncentral extension of the latter. The talk is for both physicsts and mathematicans
interested in a novel way of obtaining noncentral extensions of Lie algebras.
Four dimensional N=4 super Yang-Mills theory contains a bigger superalgebra than AdS or superconformal algebra, su(2,2/4). It corresponds to a noncentral extension of the latter. The talk is for both physicsts and mathematicans
interested in a novel way of obtaining noncentral extensions of Lie algebras.
Posted by: IC
Wed
8 Jun 2005
The effect of level truncation in TCSA
📍 London
Gerard Watts
(KCL)
Abstract:
The truncated conformal space approach is a very useful tool in the
numerical study of renormalisation group flows. I will discuss how one can
study the effect of truncation in a standard RG manner and its relevance
for studying perturbative fixed points.
The truncated conformal space approach is a very useful tool in the
numerical study of renormalisation group flows. I will discuss how one can
study the effect of truncation in a standard RG manner and its relevance
for studying perturbative fixed points.
Posted by: KCL
Tue
7 Jun 2005
Topological aspects of chiral anomaly and origin of mass
Pratul Bandyopadhyay
(Indian Statistical Institute, Calcutta)
Mon
6 Jun 2005
Field theories and numerical invariants in geometry and topology
Simon Donaldson
(IC)
Thu
2 Jun 2005
Numerical Ricci flat metrics on K3
Toby Wiseman
(Harvard)
Abstract:
Compact Calabi-Yau manifolds are a key ingredient for dimensional reduction in string theory. For this, one requires the Ricci-flat metric on these manifolds. Whilst Yau proved this metric exists, no explicit smooth examples are known, essentially as it is very difficult (impossible?) to find them analytically as they have no continuous isometries. Taking a new approach, I will discuss numerical methods to solve the Einstein equation on these manifolds. I will pedagogically describe the construction, and give results, for a particular one
parameter family of metrics on K3 (the unique 4-dimensional Calabi-Yau manifold). I will discuss possible applications of these methods, and generalizations to geometries with matter such as those relevant for flux
compactifications. There will be some nice pictures.
Compact Calabi-Yau manifolds are a key ingredient for dimensional reduction in string theory. For this, one requires the Ricci-flat metric on these manifolds. Whilst Yau proved this metric exists, no explicit smooth examples are known, essentially as it is very difficult (impossible?) to find them analytically as they have no continuous isometries. Taking a new approach, I will discuss numerical methods to solve the Einstein equation on these manifolds. I will pedagogically describe the construction, and give results, for a particular one
parameter family of metrics on K3 (the unique 4-dimensional Calabi-Yau manifold). I will discuss possible applications of these methods, and generalizations to geometries with matter such as those relevant for flux
compactifications. There will be some nice pictures.
Posted by: IC
May 2005
Tue
31 May 2005
Probing the Higgs sector at the LHC
Alan Martin
(University of Durham)
Thu
26 May 2005
Non-associative T-duals
Keith Hannabuss
(Oxford)
Abstract:
This seminar reviews some of the global algebraic and geometric structure present in T-duality. Bouwknegt, Evslin and Mathai have given a geometric procedure for handling T-duality for certain non-trivial principal torus bundles. Subsequent work by Mathai and Rosenberg showed that sometimes when there is no geometric T-dual there may be a non-commutative torus bundle playing the same role. This exploited a very similar duality for C-star-algebras known for a couple of decades.
This talk will review those developments and their recent extension in
collaboration with Bouwknegt and Mathai to more general situations in
which the algebraic structure becomes non-associative.
This seminar reviews some of the global algebraic and geometric structure present in T-duality. Bouwknegt, Evslin and Mathai have given a geometric procedure for handling T-duality for certain non-trivial principal torus bundles. Subsequent work by Mathai and Rosenberg showed that sometimes when there is no geometric T-dual there may be a non-commutative torus bundle playing the same role. This exploited a very similar duality for C-star-algebras known for a couple of decades.
This talk will review those developments and their recent extension in
collaboration with Bouwknegt and Mathai to more general situations in
which the algebraic structure becomes non-associative.
Posted by: IC
Mon
23 May 2005
An informal introduction to topological string theory, part 3.
Chris Hull
(IC)
Abstract:
String Theory and Geometry Seminar
String Theory and Geometry Seminar
Posted by: KCL
Mon
23 May 2005
The lost proof of Loewner's theorem
📍 London
Barry Simon
(Caltech)
Abstract:
(This talk is an exceptional colloquium of the Department of Mathematics.)
A real-valued function, F, on an interval (a,b) is called matrix monotone
if F(A) is less than F(B) whenever A and B are finite matrices of the same order with
eigenvalues in (a,b) and A less than B. In 1934, Loewner proved the remarkable
theorem that F is matrix monotone if and only if F is real analytic with
continuations to the upper and lower half planes so that Im F is positive in the
upper half plane.
This deep theorem has evoked enormous interest over the years and a number
of alternate proofs. There is a lovely 1954 proof that seems to have been
lost in that the proof is not mentioned in various books and review
article presentations of the subject, and I have found no references to
the proof since 1960. The proof uses continued fractions.
I'll provide background on the subject and then discuss the lost proof and
a variant of that proof which I've found, which even avoids the need for
estimates, and proves a stronger theorem.
(This talk is an exceptional colloquium of the Department of Mathematics.)
A real-valued function, F, on an interval (a,b) is called matrix monotone
if F(A) is less than F(B) whenever A and B are finite matrices of the same order with
eigenvalues in (a,b) and A less than B. In 1934, Loewner proved the remarkable
theorem that F is matrix monotone if and only if F is real analytic with
continuations to the upper and lower half planes so that Im F is positive in the
upper half plane.
This deep theorem has evoked enormous interest over the years and a number
of alternate proofs. There is a lovely 1954 proof that seems to have been
lost in that the proof is not mentioned in various books and review
article presentations of the subject, and I have found no references to
the proof since 1960. The proof uses continued fractions.
I'll provide background on the subject and then discuss the lost proof and
a variant of that proof which I've found, which even avoids the need for
estimates, and proves a stronger theorem.
Posted by: KCL
Thu
19 May 2005
Causality and locality in string and field theory
Chong-Sun Chu
(Durham)
Thu
19 May 2005
D-Brane Boundary States in the Pure Spinor Superstring
Niclas Wyllard
(CERN)
Abstract:
After a general overview, the construction of D-brane boundary states in the pure spinor superstring will be discussed.
After a general overview, the construction of D-brane boundary states in the pure spinor superstring will be discussed.
Posted by: IC
Mon
16 May 2005
An informal introduction to topological string theory, part 2
Chris Hull
(Imperial College)
Mon
9 May 2005
An informal overview of topological string theory
Chris Hull
(Imperial College)
Fri
6 May 2005
Symmetries in M theory
Peter West
(King's)
Wed
4 May 2005
Aspects of chiral dynamics in AdS CFT models
Jose Barbon
(Madrid)
Abstract:
I review general features of AdS/CFT models with dynamical quarks,
with particular emphasis on chiral dynamics. I also show how these
models incorporate the nontrivial interplay between the solution of the
U(1) problem in QCD and the 1/N expansion.
I review general features of AdS/CFT models with dynamical quarks,
with particular emphasis on chiral dynamics. I also show how these
models incorporate the nontrivial interplay between the solution of the
U(1) problem in QCD and the 1/N expansion.
Posted by: KCL
Wed
4 May 2005
How to construct superconformal field theories associated to a family of smooth quartic K3 surfaces
Katrin Wendland
(Warwick University)
April 2005
Thu
28 Apr 2005
Twistor-inspired Approaches to Perturbative Gauge Theories
David Dunbar
(Swansea)
Wed
27 Apr 2005
Flux and Freund-Rubin Superpotentials in M-theory
📍 London
Neil Lambert
(KCL)
Tue
26 Apr 2005
A Layman's Guide to M-Theory
Michael Duff
(IC)
Abstract:
INSTITUTE FOR MATHEMATICAL SCIENCES LAUNCH WEEK
INSTITUTE FOR MATHEMATICAL SCIENCES LAUNCH WEEK
Posted by: KCL
Mon
25 Apr 2005
Curvature in Geometry and Physics
Simon Donaldson
(IC)
Abstract:
INSTITUTE FOR MATHEMATICAL SCIENCES LAUNCH WEEK
INSTITUTE FOR MATHEMATICAL SCIENCES LAUNCH WEEK
Posted by: KCL
Thu
21 Apr 2005
Topological analogies of string and M-theory dualities
Paul de Medeiros
(Michigan)
Thu
14 Apr 2005
Twistors and Gauge Theory
David Kosower
(SPhT Saclay)
Thu
14 Apr 2005
Quantum fluctuations of rotating strings in AdS5xS5
Yuji Satoh
(Tsukuba/Imperial)
Abstract:
We discuss quantum fluctuations of a class of rotating strings in AdS5xS5. In particular, we develop a systematic method to compute the one-loop sigma-model effective actions in closed forms for large angular momenta. As examples, we explicitly evaluate the leading terms for the constant radii strings in the SO(6) sector with two equal angular momenta, the SU(2) sector, and the SL(2) sector. We also obtain the leading quantum corrections to the space-time energy for these sectors.
We discuss quantum fluctuations of a class of rotating strings in AdS5xS5. In particular, we develop a systematic method to compute the one-loop sigma-model effective actions in closed forms for large angular momenta. As examples, we explicitly evaluate the leading terms for the constant radii strings in the SO(6) sector with two equal angular momenta, the SU(2) sector, and the SL(2) sector. We also obtain the leading quantum corrections to the space-time energy for these sectors.
Posted by: IC
Wed
13 Apr 2005
Free geometry for higher spins: results and perspectives
📍 London
Dario Francia
(Universita di Roma Tre)
Abstract:
The linearised curvatures of de Wit and Freedman for totally
symmetric gauge fields of any spin are shown to give rise to geometric
equations in which both fields and gauge parameters are not
constrained a priori. These equations, which are non local, reduce to
the traditional, local Fronsdal form by a suitable gauge fixing, and
on-shell degrees of freedom are just the physical ones. Developments
and generalisations of these results are discussed.
The linearised curvatures of de Wit and Freedman for totally
symmetric gauge fields of any spin are shown to give rise to geometric
equations in which both fields and gauge parameters are not
constrained a priori. These equations, which are non local, reduce to
the traditional, local Fronsdal form by a suitable gauge fixing, and
on-shell degrees of freedom are just the physical ones. Developments
and generalisations of these results are discussed.
Posted by: KCL
Tue
12 Apr 2005
Free geometry for higher spins: results and perspectives
Dario Francia
(Rome, Tor Vergata)
March 2005
Thu
31 Mar 2005
Warped throats and cascading gauge theories
Angel Uranga
(Madrid)
Abstract:
We describe duality cascades and their infrared behavior for gauge theories on D3-branes at singularities in the presence of fractional branes. From the gauge field theory viewpoint, we show that D3-branes probing the infrared theory have a quantum deformed moduli space, given by a complex deformation of the initial geometry to a simpler one. Thus the gauge theory strong infrared dynamics smoothes out the naked singularities of the recently constructed dual supergravity warped throat solutions with 3-form fluxes. This behaviour thus generalizes the Klebanov-Strassler deformation of the conifold. We describe several explicit examples, including models with several scales of strong gauge dynamics, whose dual should correspond to throats with several radial regions with different exponential warp factors. These rich throat geometries have interesting applications in compactification and model building.
We describe duality cascades and their infrared behavior for gauge theories on D3-branes at singularities in the presence of fractional branes. From the gauge field theory viewpoint, we show that D3-branes probing the infrared theory have a quantum deformed moduli space, given by a complex deformation of the initial geometry to a simpler one. Thus the gauge theory strong infrared dynamics smoothes out the naked singularities of the recently constructed dual supergravity warped throat solutions with 3-form fluxes. This behaviour thus generalizes the Klebanov-Strassler deformation of the conifold. We describe several explicit examples, including models with several scales of strong gauge dynamics, whose dual should correspond to throats with several radial regions with different exponential warp factors. These rich throat geometries have interesting applications in compactification and model building.
Posted by: IC
Wed
23 Mar 2005
Loop Amplitudes in Gauge Theory from MHV Vertices
📍 London
Andreas Brandhuber
(Queen Mary College)
Tue
22 Mar 2005
On type II strings in two dimensions
Harald Ita
(Swansea)
Thu
17 Mar 2005
Moduli stabilization, and the cosmology of massless string modes
Subodh Patil
(Brown)
Wed
16 Mar 2005
Exact Degeneracies of Small Black Holes and the Topological String Amplitude
Boris Pioline
(LPTHE, LPTENS)
Abstract:
Recently, Ooguri, Strominger and Vafa have proposed to
identify the macroscopic Bekenstein-Hawking-Wald entropy of extremal
charged Black Holes in type II string compactified on a Calabi-Yau
threefold, with the all order microscopic entropy in a specific
statistical ensemble. We present a test of this conjecture in the
case of 'small' black holes (which have zero Bekenstein-Hawking entropy
at tree level, but obtain a non-zero entropy after quantum corrections)
using heterotic / type II duality. We find a remarkable agreement to all
orders in a class of N=2 and N=4 compactifications. Nevertheless, the
OSV proposal misses non-perturbative corrections which are computable
on the heterotic side. We comment on possible improvements of this
proposal.
Recently, Ooguri, Strominger and Vafa have proposed to
identify the macroscopic Bekenstein-Hawking-Wald entropy of extremal
charged Black Holes in type II string compactified on a Calabi-Yau
threefold, with the all order microscopic entropy in a specific
statistical ensemble. We present a test of this conjecture in the
case of 'small' black holes (which have zero Bekenstein-Hawking entropy
at tree level, but obtain a non-zero entropy after quantum corrections)
using heterotic / type II duality. We find a remarkable agreement to all
orders in a class of N=2 and N=4 compactifications. Nevertheless, the
OSV proposal misses non-perturbative corrections which are computable
on the heterotic side. We comment on possible improvements of this
proposal.
Posted by: QMW
Wed
16 Mar 2005
Continuum Limit of the 3bar(3) sl(2,1) Superspin Chain
Fabian Essler
(Oxford University)
Abstract:
We analyze the continuum limit of the integrable 3 3 times bar(3) times 3 times bar(3)... sl(2/1) superspin chain. We discover profoundly new
features, including a continuous spectrum of conformal weights, whose
numerical evidence is infinite degeneracies of the scaled gaps in the
thermodynamic limit. This indicates that the corresponding conformal field
theory has a non compact target space (even though our lattice model
involves only finite dimensional representations). We argue that our
results are compatible with this theory being the level k=3D1, SU(2/1) WZW
model (whose precise definition requires some care). In doing so, we
establish several new results for this model. With regard to potential
applications to the spin quantum Hall effect, we conclude that the
continuum limit of the 3 times bar (3) times 3 times bar(3)... sl(2,1)
integrable superspin chain is not the same as (and is in fact very
different from) the continuum limit of the corresponding chain with
two-superspin interactions only, which is known to be a model for the spin
quantum Hall effect. The study of possible RG flows between the two
theories is left for further study.
We analyze the continuum limit of the integrable 3 3 times bar(3) times 3 times bar(3)... sl(2/1) superspin chain. We discover profoundly new
features, including a continuous spectrum of conformal weights, whose
numerical evidence is infinite degeneracies of the scaled gaps in the
thermodynamic limit. This indicates that the corresponding conformal field
theory has a non compact target space (even though our lattice model
involves only finite dimensional representations). We argue that our
results are compatible with this theory being the level k=3D1, SU(2/1) WZW
model (whose precise definition requires some care). In doing so, we
establish several new results for this model. With regard to potential
applications to the spin quantum Hall effect, we conclude that the
continuum limit of the 3 times bar (3) times 3 times bar(3)... sl(2,1)
integrable superspin chain is not the same as (and is in fact very
different from) the continuum limit of the corresponding chain with
two-superspin interactions only, which is known to be a model for the spin
quantum Hall effect. The study of possible RG flows between the two
theories is left for further study.
Posted by: KCL
Wed
16 Mar 2005
String corrected black holes
Mukund Rangamani
(UC, Berkeley and LBL, Berkeley and Santa Barbara, KITP)
Thu
10 Mar 2005
Supersymmetric black rings
Jan Gutowski
(Oxford)
Thu
10 Mar 2005
Non-rational conformal field theory and holography
Jan Troost
(ENS Paris)
Abstract:
We will argue that the cigar conformal field theory SL(2,R)/U(1) is a prime example of a non-rational conformal field theory and we exhibit some of its characteristic features that might generalize to other non-rational conformal field theories. We discuss how this particular non-rational conformal field theory (with or without boundary) arises in string theory backgrounds with NS5-branes, and how the technical advances reached in the conformal field theory can illuminate aspects of holography in these backgrounds.
We will argue that the cigar conformal field theory SL(2,R)/U(1) is a prime example of a non-rational conformal field theory and we exhibit some of its characteristic features that might generalize to other non-rational conformal field theories. We discuss how this particular non-rational conformal field theory (with or without boundary) arises in string theory backgrounds with NS5-branes, and how the technical advances reached in the conformal field theory can illuminate aspects of holography in these backgrounds.
Posted by: IC
Wed
9 Mar 2005
The Jacobi principle and cosmological singularities
📍 London
Paul Townsend
(DAMTP)
Mon
7 Mar 2005
From the Gaudin model to the uniformization of Riemann surfaces
📍 London
Sylvain Ribault
(KCL)
Abstract:
I will introduce the Gaudin Model. This model is described by a
system of commuting Hamiltonians. I will explain how the eigenvalue
equations for these Hamiltonians arise as the critical level limit of the
Knizhnik-Zamolodchikov equations. In particular, some eigenvectors can be
built from H3 correlators. Then I will use the H3-Liouville relation to
relate these correlators to Liouville theory correlators. The critical
level limit is interpreted in Liouville theory as a geometrical limit.
This leads to the construction of Gaudin eigenvalues from the accessory
parameters which arise in the uniformization of certain Riemann surfaces.
I will introduce the Gaudin Model. This model is described by a
system of commuting Hamiltonians. I will explain how the eigenvalue
equations for these Hamiltonians arise as the critical level limit of the
Knizhnik-Zamolodchikov equations. In particular, some eigenvectors can be
built from H3 correlators. Then I will use the H3-Liouville relation to
relate these correlators to Liouville theory correlators. The critical
level limit is interpreted in Liouville theory as a geometrical limit.
This leads to the construction of Gaudin eigenvalues from the accessory
parameters which arise in the uniformization of certain Riemann surfaces.
Posted by: KCL
Fri
4 Mar 2005
Strict quantisation and unbounded operators
Sebastien Racaniere
(Cambridge)
Abstract:
In quantum physics, the operators associated with the position
and the momentum of a particle are unbounded operators and
C-algebraic quantisation, or strict quantisation, does therefore not
deal with such operators. In this talk, I will show how to remedy this
problem for Lie-Poisson manifolds (this includes dual of Lie algebras
and cotangent bundle of manifolds). As an application, I will show with
an example how the quantisation of the dual of the Lie algebroid
associated to a Poisson manifold can lead to a quantisation of the
Poisson manifold itself. The example I consider is the torus with
constant symplectic structure, in which case I recover its usual C-algebraic quantisation.
In quantum physics, the operators associated with the position
and the momentum of a particle are unbounded operators and
C-algebraic quantisation, or strict quantisation, does therefore not
deal with such operators. In this talk, I will show how to remedy this
problem for Lie-Poisson manifolds (this includes dual of Lie algebras
and cotangent bundle of manifolds). As an application, I will show with
an example how the quantisation of the dual of the Lie algebroid
associated to a Poisson manifold can lead to a quantisation of the
Poisson manifold itself. The example I consider is the torus with
constant symplectic structure, in which case I recover its usual C-algebraic quantisation.
Posted by: KCL
Thu
3 Mar 2005
The semi-classical approach to the gauge - string correspondence
Bogdan Stefanski
(IC)
Thu
3 Mar 2005
Black Holes, the AdS correspondence, black rings and thermodynamics
Malcolm Perry
(Cambridge)
Abstract:
I will discuss the philosophy of the Euclidean field theory approach to black hole thermodynamics. I will then illustrate some of the difficulties presented by rotating black holes in AdS. Next, I will relate these results to the AdS-CFT correspondence. Finally, I will discuss the question of black rings, and make some heterodox comments on the difficulties that they pose for the Euclidean formulation.
I will discuss the philosophy of the Euclidean field theory approach to black hole thermodynamics. I will then illustrate some of the difficulties presented by rotating black holes in AdS. Next, I will relate these results to the AdS-CFT correspondence. Finally, I will discuss the question of black rings, and make some heterodox comments on the difficulties that they pose for the Euclidean formulation.
Posted by: IC
Wed
2 Mar 2005
Generalized complex structure and supersymmetry
📍 London
Maxim Zabzine
(Queen Mary College)
February 2005
Mon
28 Feb 2005
The spinorial geometry of supersymmetric backgrounds
📍 London
Ulf Gran
(KCL)
Abstract:
I will give an elementary and informal introduction to an
efficient method of solving the Killing spinor equations. The method is
based on the description of spinors in terms of forms and can be used to
classify the supersymmetric solutions in e.g. 11D and IIB supergravity.
I will give an elementary and informal introduction to an
efficient method of solving the Killing spinor equations. The method is
based on the description of spinors in terms of forms and can be used to
classify the supersymmetric solutions in e.g. 11D and IIB supergravity.
Posted by: KCL
Fri
25 Feb 2005
Loop quantum gravity: a view from Lorentz covariant approach
📍 London
Sergei Alexandrov
(Utrecht)
Abstract:
I am going to review the status of loop quantum gravity as it is seen
from the point of view of a Lorentz covariant approach to loop quantization.
I'll start from a brief review of the standard
loop approach based on the SU(2) gauge group, its main results and problems.
Then I'll present another approach which is based on a canonical
formulation of general relativity which is explicitly covariant under
the local Lorentz transformations.
It allows to overcome several problems of the standard loop quantization
and at the same time shows that the latter breaks the diffeomorphism
invariance and is not a correct way for quantizing gravity.
In the covariant framework I'll derive a new spectrum of the area operator,
both for spacelike and timelike surfaces, and show that
its predictions agree with the spin foam quantization.
I am going to review the status of loop quantum gravity as it is seen
from the point of view of a Lorentz covariant approach to loop quantization.
I'll start from a brief review of the standard
loop approach based on the SU(2) gauge group, its main results and problems.
Then I'll present another approach which is based on a canonical
formulation of general relativity which is explicitly covariant under
the local Lorentz transformations.
It allows to overcome several problems of the standard loop quantization
and at the same time shows that the latter breaks the diffeomorphism
invariance and is not a correct way for quantizing gravity.
In the covariant framework I'll derive a new spectrum of the area operator,
both for spacelike and timelike surfaces, and show that
its predictions agree with the spin foam quantization.
Posted by: KCL
Thu
24 Feb 2005
Nonperturbative calculations in supersymmetric gauge theories, II
Francesco Fucito
(Rome, Tor Vergata)
Thu
24 Feb 2005
The spinorial geometry of supersymmetric backgrounds
Ulf Gran
(King's College)
Abstract:
I will review a recently proposed method for solving the Killing spinor equations in arbitrary dimensions. The efficiency of the method will be illustrated by recent progress on the classification of the supersymmetric solutions of 11D and IIB supergravity.
I will review a recently proposed method for solving the Killing spinor equations in arbitrary dimensions. The efficiency of the method will be illustrated by recent progress on the classification of the supersymmetric solutions of 11D and IIB supergravity.
Posted by: KCL
Wed
23 Feb 2005
Non-perturbative effects in the c=1 matrix model
📍 London
Sergei Alexandrov
(Utrecht)
Abstract:
I present results on non-perturbative effects in the c=1
string theory. First, I describe a geometric picture found in the CFT
framework which gives an interpretation of D-branes in non-critical
strings in terms of a complex curve associated with any closed string
background. I show that its c=1 limit is degenerate and the degeneracy
can be removed by considering a condensation of tachyon modes. Using
the matrix model description, I calculate the leading as well as the
subleading non-perturbative corrections to the string partition
function. We find them by using the Toda integrable structure and from
the realization of 2D string theory in terms of free fermions. Both
methods give the same result which is also interpreted through
correlation functions of a bosonic field. The leading corrections can
be interpreted in terms of localized D-branes, whereas the sub-leading
ones do not have a simple D-brane description.
I present results on non-perturbative effects in the c=1
string theory. First, I describe a geometric picture found in the CFT
framework which gives an interpretation of D-branes in non-critical
strings in terms of a complex curve associated with any closed string
background. I show that its c=1 limit is degenerate and the degeneracy
can be removed by considering a condensation of tachyon modes. Using
the matrix model description, I calculate the leading as well as the
subleading non-perturbative corrections to the string partition
function. We find them by using the Toda integrable structure and from
the realization of 2D string theory in terms of free fermions. Both
methods give the same result which is also interpreted through
correlation functions of a bosonic field. The leading corrections can
be interpreted in terms of localized D-branes, whereas the sub-leading
ones do not have a simple D-brane description.
Posted by: KCL
Wed
23 Feb 2005
Nonperturbative calculations in supersymmetric gauge theories, I
Francesco Fucito
(Rome, Tor Vergata)
Thu
17 Feb 2005
Perturbative approaches to Quantum Gravity and Yang-Mills
David Dunbar
(Swansea)
Thu
17 Feb 2005
Time-dependent spacetimes in AdS-CFT
Simon Ross
(Durham)
Abstract:
I will discuss the relation between bulk and boundary for the smooth 'bubble of nothing' solution in AdS, and for the locally AdS black hole. I will explain the relation between horizons and thermodynamics in bulk and boundary, and discuss vacuum ambiguities.
I will discuss the relation between bulk and boundary for the smooth 'bubble of nothing' solution in AdS, and for the locally AdS black hole. I will explain the relation between horizons and thermodynamics in bulk and boundary, and discuss vacuum ambiguities.
Posted by: IC
Wed
16 Feb 2005
More curiosities at c=1
📍 London
Volker Schomerus
(Saclay)
Mon
14 Feb 2005
Kac-Moody Symmetries of (super) Gravity Theories
📍 London
Igor Schnakenburg
(KCL)
Abstract:
(Note: this talk will have a great overlap with the April 5, 2004 talk by the same speaker.)
The talk will give a fairly basic introduction to the evidence
why a special class of Kac-Moody algebras, called very-extended algebras,
might play a role in the formulation of supergravity theories. This
evidence will contain a natural understanding of the field contents of
some (super)gravity theories as well as the known dualities that usually
are expected to arrive only after dimensional reduction.
(Note: this talk will have a great overlap with the April 5, 2004 talk by the same speaker.)
The talk will give a fairly basic introduction to the evidence
why a special class of Kac-Moody algebras, called very-extended algebras,
might play a role in the formulation of supergravity theories. This
evidence will contain a natural understanding of the field contents of
some (super)gravity theories as well as the known dualities that usually
are expected to arrive only after dimensional reduction.
Posted by: KCL
Wed
9 Feb 2005
Splitting the Conifold Singularity
📍 London
David Tong
(Cambridge)
Abstract:
This talk is part of the joint Triangular Seminars.
This talk is part of the joint Triangular Seminars.
Posted by: KCL
Wed
9 Feb 2005
Topological G_2 Strings
📍 London
Asad Naqvi
(Amsterdam U.)
Abstract:
This part is part of the Triangular Seminars.
This part is part of the Triangular Seminars.
Posted by: KCL
January 2005
Fri
28 Jan 2005
Q-Fano 3-folds, K3 surfaces and mirrors
Alessio Corti
(Cambridge)
Abstract:
I want to study Q-Fano 3-folds from the point of view of
mirror symmetry. In this talk I make some remarks and try some
questions.
I want to study Q-Fano 3-folds from the point of view of
mirror symmetry. In this talk I make some remarks and try some
questions.
Posted by: KCL
Thu
27 Jan 2005
All-genus calculation of Wilson loops using D-branes
Nadav Drukker
(Niels Bohr Institute)
Abstract:
The standard prescription for calculating a Wilson loop in the AdS/CFT correspondence is by a string world-sheet ending along the loop at the boundary of AdS. For a multiply wrapped Wilson loop this leads to many coincident strings, which may interact among themselves. In such cases a better description of the system is in terms of a D3-brane carrying electric flux. We find such solutions for the single straight line and the circular loop. The action agrees with the string calculation at small coupling and in addition captures all the higher genus corrections at leading order in alpha'. The resulting expression is in remarkable agreement with that found from a zero dimensional Gaussian matrix model.
The standard prescription for calculating a Wilson loop in the AdS/CFT correspondence is by a string world-sheet ending along the loop at the boundary of AdS. For a multiply wrapped Wilson loop this leads to many coincident strings, which may interact among themselves. In such cases a better description of the system is in terms of a D3-brane carrying electric flux. We find such solutions for the single straight line and the circular loop. The action agrees with the string calculation at small coupling and in addition captures all the higher genus corrections at leading order in alpha'. The resulting expression is in remarkable agreement with that found from a zero dimensional Gaussian matrix model.
Posted by: IC
Wed
26 Jan 2005
Twisted reflections on twisted SU(2n+1) branes
📍 London
Rafal R. Suszek
(King's College and Warsaw U.)
Abstract:
Chosen aspects of twisted brane geometry in the Wess-Zumino-Witten models
of type A_2n shall be discussed, both classical and stringy, in
reference to a class of coideal subalgebras of Drinfel'd-Jimbo quantum
groups known as twisted orthogonal quantum groups. An explicit relation
between the two families of algebras, together with a realisation of the
latter as (twisted) Reflection Equation Algebras shall be invoked to
emphasise the role played by them in a compact algebraic description of
quantum twisted branes on SU(2n+1) in the framework of R-matrix Reflection
Equations and associated quantum group geometries.
Chosen aspects of twisted brane geometry in the Wess-Zumino-Witten models
of type A_2n shall be discussed, both classical and stringy, in
reference to a class of coideal subalgebras of Drinfel'd-Jimbo quantum
groups known as twisted orthogonal quantum groups. An explicit relation
between the two families of algebras, together with a realisation of the
latter as (twisted) Reflection Equation Algebras shall be invoked to
emphasise the role played by them in a compact algebraic description of
quantum twisted branes on SU(2n+1) in the framework of R-matrix Reflection
Equations and associated quantum group geometries.
Posted by: KCL
Wed
26 Jan 2005
Crosslinking Structures, The cunning tricks of the bugs uncovered
Reidun Twarock
(City University)
Mon
24 Jan 2005
Closed bosonic string field theory at quartic order
📍 London
Nicolas Moeller
(King's College London)
Abstract:
I will explain how to do concrete computations in bosonic closed string
field theory. For this, I will show how to numerically describe the
geometry of the four-point contact interaction, by computing the boundary
of the relevant region of the moduli space of the four-punctured spheres,
and by computing everywhere in this region the local coordinates around
each punctures, in terms of a Strebel quadratic differential and mapping
radii. I will then explain how these results are used and checked in the
recent paper of Yang and Zwiebach by considering marginal fields in closed
bosonic string field theory.
I will explain how to do concrete computations in bosonic closed string
field theory. For this, I will show how to numerically describe the
geometry of the four-point contact interaction, by computing the boundary
of the relevant region of the moduli space of the four-punctured spheres,
and by computing everywhere in this region the local coordinates around
each punctures, in terms of a Strebel quadratic differential and mapping
radii. I will then explain how these results are used and checked in the
recent paper of Yang and Zwiebach by considering marginal fields in closed
bosonic string field theory.
Posted by: KCL
Wed
19 Jan 2005
Viral Tiling Theory, The Architecture of Viral Capsids and Viral Malformations
Reidun Twarock
(City University)
Mon
17 Jan 2005
Non-extremal D-instantons
Andres Collinucci
(Groningen)
Abstract:
D-instantons are Euclidean (-1)-brane solutions of type IIB supergravity, which have been used to compute non-perturbative corrections to the effective action of type IIB string theory. I will discuss the most general non-extremal, non-supersymmetric generalization to the D-instanton. By repeating the calculations for arbitrary dimensions and dilaton coupling we will see that these solutions can be viewed as wormholes of non-extremal Reissner-Nordstroem black holes in one higher dimension. I will also discuss the role of D-instantons in the context of AdS/CFT and make a conjecture about the CFT counterpart of these non-extremal solutions.
D-instantons are Euclidean (-1)-brane solutions of type IIB supergravity, which have been used to compute non-perturbative corrections to the effective action of type IIB string theory. I will discuss the most general non-extremal, non-supersymmetric generalization to the D-instanton. By repeating the calculations for arbitrary dimensions and dilaton coupling we will see that these solutions can be viewed as wormholes of non-extremal Reissner-Nordstroem black holes in one higher dimension. I will also discuss the role of D-instantons in the context of AdS/CFT and make a conjecture about the CFT counterpart of these non-extremal solutions.
Posted by: IC
Thu
13 Jan 2005
In search of the most stable string state
Diego Chialva
(SISSA-ISAS)
Abstract:
Massive (perturbative) string states are interesting in many respects (cosmology, black hole Physics, production at accelerators). We review the research done in order to find the perturbative massive superstring states with very long lifetime, the characteristics of their decay, the emission spectrum, both in fully extended space-time and in the case of toroidal compactifications.
The main result is the identification of a particular state with very long lifetime decaying only by gravitational emission and with thermal-like spectrum.
Massive (perturbative) string states are interesting in many respects (cosmology, black hole Physics, production at accelerators). We review the research done in order to find the perturbative massive superstring states with very long lifetime, the characteristics of their decay, the emission spectrum, both in fully extended space-time and in the case of toroidal compactifications.
The main result is the identification of a particular state with very long lifetime decaying only by gravitational emission and with thermal-like spectrum.
Posted by: IC
Mon
10 Jan 2005
A new family of superconformal quivers with known Sasaki-Einstein duals
Pavlos Kazakopoulos
(MIT)
Abstract:
I will discuss the newly discovered Y(p,q) quiver gauge theories, which are dual to Type IIB string theory on AdS5 x Y(p,q). The metrics on the five-dimensional Y(p,q) manifolds are explicitly known, thus opening up exciting possibilities. Special emphasis will be placed on the toric phases of these theories and their Seiberg duality structure.
I will discuss the newly discovered Y(p,q) quiver gauge theories, which are dual to Type IIB string theory on AdS5 x Y(p,q). The metrics on the five-dimensional Y(p,q) manifolds are explicitly known, thus opening up exciting possibilities. Special emphasis will be placed on the toric phases of these theories and their Seiberg duality structure.
Posted by: IC