Triangle Seminars
July 2012
Tue
10 Jul 2012
Black Holes in a Universe from higher dimensions
Kei-ichi Maeda
(Waseda)
Abstract:
An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state. It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. The solution depends on two parameters, the charge Q and one parameter (the ratio of the energy density of U(1) fields to that of the scalar field). We find a regular horizon, which is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature. For the case without a potential, we can derive such a solution from a time-dependent intersecting M-brane solution in eleven dimensions by the dimensional reduction.
An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state. It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. The solution depends on two parameters, the charge Q and one parameter (the ratio of the energy density of U(1) fields to that of the scalar field). We find a regular horizon, which is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature. For the case without a potential, we can derive such a solution from a time-dependent intersecting M-brane solution in eleven dimensions by the dimensional reduction.
Posted by: IC
June 2012
Wed
27 Jun 2012
Supersymmetry on Curved Spaces and Holography
Alberto Zaffaroni
(Milano Bicocca)
Thu
21 Jun 2012
The index of M-theory (Part 2)
Nikita Nekrasov
(IHES)
Wed
20 Jun 2012
The index of M-theory (Part 1)
Nikita Nekrasov
(IHES)
Thu
14 Jun 2012
Introduction to Quantum Sheaf Cohomology
Eric Sharpe
(Virginia Tech)
Abstract:
http://www.city.ac.uk/engineering-maths/research/mathematics-centre/research-seminars/seminars-2011-2012
http://www.city.ac.uk/engineering-maths/research/mathematics-centre/research-seminars/seminars-2011-2012
Posted by: KCL
Wed
13 Jun 2012
M5-Branes, Toric Diagrams and Gauge Theory Duality
Elli Pomoni
(Humboldt U.)
May 2012
Wed
30 May 2012
F-Theory compactifications and Toric Geometry
Volker Braun
(DIAS)
Thu
24 May 2012
TBA
James Barnard
(Durham)
Thu
10 May 2012
Light-front holographic approach to nonperturbative QCD
Guy F de Teramond
(Costa Rica U.)
Wed
2 May 2012
Minimizing gauge-functional for 2-d gravity and string theory
Laurent Baulieu
(LPTHE Paris)
April 2012
Fri
27 Apr 2012
Umklapp in AdS/CFT
Diego Hofman
(Harvard)
Wed
25 Apr 2012
Holographic Fermi surfaces
David Vegh
(Stony Brook)
Fri
20 Apr 2012
Baryonic popcorn multi-instanton chains and holographic nuclear matter
Cobi Sonnenschein
(Tel Aviv U.)
Thu
19 Apr 2012
TBA
Massimo Taronna
Fri
13 Apr 2012
Constructive Wall-Crossing and Seiberg-Witten
Piljin Yi
(KIAS)
Wed
11 Apr 2012
SL(2,R) duality on AdS/BCFT
Mitsutoshi Fujita
(Washington U.)
March 2012
Thu
29 Mar 2012
TBA
Critian Vergu
(Zurich)
Wed
28 Mar 2012
Generalized structures of ten-dimensional supersymmetric solutions
📍 London
Alessandro Tomasiello
(Milan)
Abstract:
Four-dimensional supersymmetric type II string theory vacua can be described elegantly in terms of pure spinors on the generalized tangent bundle T+T. This leads to constraints on M6 involving Hitchin's "generalized complex geometry". In this talk, we apply the same techniques to any ten-dimensional supersymmetric solution, not necessarily factorized as AdS4xM6 or Mink4xM6. I will describe a system of differential equations in terms of forms describing a "generalized ISpin(7) structure" is equivalent to unbroken supersymmetry, in both IIA and IIB. One of the equations in the system reproduces in one fell swoop all the pure spinors equations for four-dimensional vacua.
Four-dimensional supersymmetric type II string theory vacua can be described elegantly in terms of pure spinors on the generalized tangent bundle T+T. This leads to constraints on M6 involving Hitchin's "generalized complex geometry". In this talk, we apply the same techniques to any ten-dimensional supersymmetric solution, not necessarily factorized as AdS4xM6 or Mink4xM6. I will describe a system of differential equations in terms of forms describing a "generalized ISpin(7) structure" is equivalent to unbroken supersymmetry, in both IIA and IIB. One of the equations in the system reproduces in one fell swoop all the pure spinors equations for four-dimensional vacua.
Posted by: KCL
Tue
27 Mar 2012
What happens when Lie groups meet integrable boundaries
Niall MacKay
(York)
Abstract:
When an integrable quantum field theory in one space dimension
has a Lie group symmetry, the Lie algebra is typically embedded in a
larger algebra called a Yangian. When one adds a boundary which
preserves integrability, this is extended to a (generalized) twisted
Yangian. We explain the role of these algebras in physics, and in
particular recent work by MacKay and Regelskis which uncovers their
governing role in the scattering of worldsheet excitations off D-branes
in the AdS/CFT correspondence.
When an integrable quantum field theory in one space dimension
has a Lie group symmetry, the Lie algebra is typically embedded in a
larger algebra called a Yangian. When one adds a boundary which
preserves integrability, this is extended to a (generalized) twisted
Yangian. We explain the role of these algebras in physics, and in
particular recent work by MacKay and Regelskis which uncovers their
governing role in the scattering of worldsheet excitations off D-branes
in the AdS/CFT correspondence.
Posted by: KCL
Thu
22 Mar 2012
TBA
Can Kozcaz
(CERN)
Wed
21 Mar 2012
Aspects of modern geometry: up-dating Hilbert
Sir Simon Donaldson
(Imperial College)
Abstract:
In the first part of the talk I will discuss the meaning of "geometry" in contemporary mathematics and some general developments. In the second part I will focus on a few particular problems which I know more about, such as questions involving topology and geometric structures on manifolds. The talk will in part be built around an imaginary conversation with Hilbert.
In the first part of the talk I will discuss the meaning of "geometry" in contemporary mathematics and some general developments. In the second part I will focus on a few particular problems which I know more about, such as questions involving topology and geometric structures on manifolds. The talk will in part be built around an imaginary conversation with Hilbert.
Posted by: IC
Wed
21 Mar 2012
Supersymmetric three sphere partition functions
Daniel L. Jafferis
(Harvard)
Tue
20 Mar 2012
A q-deformed Verlinde algebra
Christian Korff
(Glasgow)
Abstract:
We generalise a recent combinatorial description of the Verlinde or WZW fusion algebra of type A by defining cylindric Macdonald functions. The latter arise as weighted sums over non-intersecting paths on a square lattice with periodic boundary conditions. Expanding the cylindric Macdonald functions into Schur functions one obtains generalised Kostka-Foulkes polynomials. The latter contain ordinary Kostka-Foulkes polynomials, which appear in algebraic geometry, representation theory and combinatorics, as special case. We further motivate the cylindric Schur functions by showing that they are connected with a commutative Frobenius algebra which can be interpreted as a deformation of the Verlinde algebra: its structure constants are polynomials whose constant terms are the WZW fusion coefficients.
We generalise a recent combinatorial description of the Verlinde or WZW fusion algebra of type A by defining cylindric Macdonald functions. The latter arise as weighted sums over non-intersecting paths on a square lattice with periodic boundary conditions. Expanding the cylindric Macdonald functions into Schur functions one obtains generalised Kostka-Foulkes polynomials. The latter contain ordinary Kostka-Foulkes polynomials, which appear in algebraic geometry, representation theory and combinatorics, as special case. We further motivate the cylindric Schur functions by showing that they are connected with a commutative Frobenius algebra which can be interpreted as a deformation of the Verlinde algebra: its structure constants are polynomials whose constant terms are the WZW fusion coefficients.
Posted by: KCL
Mon
19 Mar 2012
N=2 Gauge Theories: Congruence Subgroups, Coset Graphs and Modular Surfaces
Yang-Hui He
(City University)
Abstract:
We establish a correspondence between generalized quiver gauge theories in four-dimensions and congruence subgroups of the modular group, hinging upon the trivalent graphs which arise in both. The gauge theories and the graphs are enumerated and their numbers are compared. The correspondence is particularly striking for genus zero torsion-free congruence subgroups which are crucial to Moonshine. We analyze in detail the case of index 24, where modular elliptic K3 surfaces emerge: here, the elliptic j-invariants can be recast as dessins d'enfant which dictate the Seiberg-Witten curves.
We establish a correspondence between generalized quiver gauge theories in four-dimensions and congruence subgroups of the modular group, hinging upon the trivalent graphs which arise in both. The gauge theories and the graphs are enumerated and their numbers are compared. The correspondence is particularly striking for genus zero torsion-free congruence subgroups which are crucial to Moonshine. We analyze in detail the case of index 24, where modular elliptic K3 surfaces emerge: here, the elliptic j-invariants can be recast as dessins d'enfant which dictate the Seiberg-Witten curves.
Posted by: IC
Fri
16 Mar 2012
Amplitudes for Fivebranes
Moshe Rozali
(U. of British Columbia)
Thu
15 Mar 2012
TBA
Alessandro Torrielli
Wed
14 Mar 2012
Wilson Loops in N = 2 Gauge Theories, Matrix Models and Holography
📍 London
Filippo Passerini
(Humboldt, Berlin)
Abstract:
Using localization techniques, Pestun has shown how to reduce certain quantum field theory path integrals to finite-dimensional matrix integrals. In this way, the expectation value of certain operators in the gauge theory is equivalent to the expectation value of observables in the associated matrix model. In this talk, Pestun's matrix model is used to compute the expectation value of the circular Wilson loop in N = 2 SuperConformal QCD, in the weak and strong coupling regime. At weak coupling, we define a perturbative scheme that permits to compute the Wilson loop at arbitrary high number of loops. At strong coupling, our computation carries information about the string theory dual of the SuperConformal QCD, that is not known yet. In particular, our results indicate that the string tension in the dual string theory scales as the logarithm of the gauge theory 't Hooft coupling.
Using localization techniques, Pestun has shown how to reduce certain quantum field theory path integrals to finite-dimensional matrix integrals. In this way, the expectation value of certain operators in the gauge theory is equivalent to the expectation value of observables in the associated matrix model. In this talk, Pestun's matrix model is used to compute the expectation value of the circular Wilson loop in N = 2 SuperConformal QCD, in the weak and strong coupling regime. At weak coupling, we define a perturbative scheme that permits to compute the Wilson loop at arbitrary high number of loops. At strong coupling, our computation carries information about the string theory dual of the SuperConformal QCD, that is not known yet. In particular, our results indicate that the string tension in the dual string theory scales as the logarithm of the gauge theory 't Hooft coupling.
Posted by: KCL
Wed
14 Mar 2012
Wilson Loops in Five-Dimensional SYM: A new perspective on the question of UV-finiteness
Donovan Young
(NBI)
Wed
7 Mar 2012
Searching for U-duality supermultiplets
📍 London
Martin Cederwall
(Chalmers, Sweden)
Abstract:
The internal dynamics of U-folds (or T-folds) seems to provide interesting generalisations of Einstein gravity. What can we learn from supersymmetry?
I describe work in progress, where pure spinor techniques are adapted to the
U-duality setting.
The internal dynamics of U-folds (or T-folds) seems to provide interesting generalisations of Einstein gravity. What can we learn from supersymmetry?
I describe work in progress, where pure spinor techniques are adapted to the
U-duality setting.
Posted by: KCL
Wed
7 Mar 2012
The free energy of Chern-Simons theories and the AdS4/CFT3 correspondence
Claudius Klare
(Milano Bicocca)
Tue
6 Mar 2012
E11 and generalised geometry
Peter West
(King's)
Mon
5 Mar 2012
Fluid-Gravity Duality at a Cutoff Surface
Cynthia Keeler
(Michigan)
Thu
1 Mar 2012
PhD Courses–D-branes:perturbative and non-perturbative applications to SUSY gauges theories
Alberto Lerda
Abstract:
http://strings.ph.qmul.ac.uk/postgraduate/phd-courses
http://strings.ph.qmul.ac.uk/postgraduate/phd-courses
Posted by: QMW
Thu
1 Mar 2012
TBA
Kyriakos Papadodimas
(CERN)
February 2012
Wed
29 Feb 2012
Brane/Antibrane Backreaction in Axion Monodromy Inflation
📍 London
Joseph Conlon
(Oxford)
Abstract:
TransPlanckian inflationary excursions are very interesting because they are sensitive to Planck-suppressed operators and can generate observable tensor modes. I review one proposed model generating a transPlanckian excursion and argue that consideration of antibrane backreaction renders the assumptions entering the model inconsistent.
TransPlanckian inflationary excursions are very interesting because they are sensitive to Planck-suppressed operators and can generate observable tensor modes. I review one proposed model generating a transPlanckian excursion and argue that consideration of antibrane backreaction renders the assumptions entering the model inconsistent.
Posted by: KCL
Wed
29 Feb 2012
Correlation functions, Wilson loops, and local operators
Tim Adamo
(Oxford U.)
Mon
27 Feb 2012
PhD Courses–D-branes and Black Holes.
Costas Bachas
(Ecole Normale Superieure)
Abstract:
http://strings.ph.qmul.ac.uk/postgraduate/phd-courses
http://strings.ph.qmul.ac.uk/postgraduate/phd-courses
Posted by: QMW
Fri
24 Feb 2012
String theory dualities and supergravity ultraviolet divergences
Pierre Vanhove
(SACLAY, SphT)
Wed
22 Feb 2012
Generalized quark antiquark potential and the TBTBA.
📍 London
Nadav Drukker
(KCL)
Abstract:
Note: Sunil Mukhi's talk was cancelled!
Note: Sunil Mukhi's talk was cancelled!
Posted by: KCL
Wed
22 Feb 2012
New superconformal models in six dimensions
📍 London
Henning Samtleben
(ENS Lyon)
Abstract:
I review the recent construction of six-dimensional (1,0) superconformal models with non-abelian gauge couplings for multiple tensor multiplets. A crucial ingredient in the construction is the introduction of higher-rank tensor fields. I discuss various examples and the possible relation to the (2,0) theories underlying the dynamics of multiple M5 branes.
I review the recent construction of six-dimensional (1,0) superconformal models with non-abelian gauge couplings for multiple tensor multiplets. A crucial ingredient in the construction is the introduction of higher-rank tensor fields. I discuss various examples and the possible relation to the (2,0) theories underlying the dynamics of multiple M5 branes.
Posted by: IC
Tue
21 Feb 2012
TBA
Robert de Mello Koch
Fri
17 Feb 2012
n -n duality and universality
Ruben Mkrtchyan
(Yerevan Phys. Inst.)
Thu
16 Feb 2012
TBA
Mathew Bullimore
(Oxford)
Wed
15 Feb 2012
C-Star Algebras and Complex Cobordism
📍 London
Roland Friedrich
(Humboldt, Berlin)
Abstract:
In this talk we derive a novel and fundamental relation between
C*-algebras and Complex Cobordism.
We endow the space of complex genera with the structure of an infinite Lie
group, with the underlying manifold being isomorphic to the group of
automorphisms of the formal disc, and relate it then to operator algebras.
The group operation introduced can be understood combinatorially in terms
of planar rooted trees. Finally we shall give connections with Conformal
Field Theory.
In this talk we derive a novel and fundamental relation between
C*-algebras and Complex Cobordism.
We endow the space of complex genera with the structure of an infinite Lie
group, with the underlying manifold being isomorphic to the group of
automorphisms of the formal disc, and relate it then to operator algebras.
The group operation introduced can be understood combinatorially in terms
of planar rooted trees. Finally we shall give connections with Conformal
Field Theory.
Posted by: KCL
Fri
10 Feb 2012
Fermionic T-duality in supergravity
Eoin O Colgain
(Oviedo U.)
Thu
9 Feb 2012
The supersymmetric hydrodynamics of charged branes
Giuseppe Policastro
Wed
8 Feb 2012
Automorphic properties of string theory amplitudes in various dimensions
📍 London
Pierre Vanhove
(IHES, Paris)
Abstract:
Maximally supersymmetric string theory compactified on d-dimensional torus is invariant under the non-perturbative U-duality groups E_{d+1}(Z). These duality groups are the discrete version over the integers of the real split forms of the simply laced lie groups of rank d. The interactions of the theory are given by automorphic function under E_{d+1}(Z), given in the simplest cases by the residue of maximal parabolic Eisenstein series. The dimensional reduction of the theory to three dimensions gives rise to the duality group E_8 from which all BPS couplings in higher dimensions can be extracted.
We will present the construction of the automorphic form relevant for the supersymmetric protected BPS interactions in the low-energy expansion of maximal supersymmetric effective action.
We will show that the support of the non-vanishing Fourier coefficients for these automorphic form is given by the expected BPS conditions one can derive from the supersymmetric conditions.
Maximally supersymmetric string theory compactified on d-dimensional torus is invariant under the non-perturbative U-duality groups E_{d+1}(Z). These duality groups are the discrete version over the integers of the real split forms of the simply laced lie groups of rank d. The interactions of the theory are given by automorphic function under E_{d+1}(Z), given in the simplest cases by the residue of maximal parabolic Eisenstein series. The dimensional reduction of the theory to three dimensions gives rise to the duality group E_8 from which all BPS couplings in higher dimensions can be extracted.
We will present the construction of the automorphic form relevant for the supersymmetric protected BPS interactions in the low-energy expansion of maximal supersymmetric effective action.
We will show that the support of the non-vanishing Fourier coefficients for these automorphic form is given by the expected BPS conditions one can derive from the supersymmetric conditions.
Posted by: KCL
Wed
8 Feb 2012
Quantum Nambu geometry in string theory
Chong-Sun Chu
(Durham)
Thu
2 Feb 2012
Aspects of AGT correspondence
Giulio Bonelli
(SISSA)
Wed
1 Feb 2012
Integrability in SYM at weak coupling, AdS/CFT duality and correlation functions
📍 London
Nikolay Gromov
(KCL)
Abstract:
TBA
TBA
Posted by: KCL
Wed
1 Feb 2012
Conifold Geometries and NS5-branes
Jock McOrist
(Cambridge U.)
Abstract:
I will describe a how to construct the supergravity solution for a pair of NS5-branes, intersecting on R^{1,3} and localised in all directions except a single transverse circle. Such solutions are rare, and yet may have many potential applications in gauge-gravity duality and model building. The construction invovles developing an explicit map between the conifold metric and the geometry of two intersecting NS5-branes. I will also describe additional intersecting brane solutions corresponding to smoothing out the intersection by, for example, separating branes or putting a metric on the intersection.
I will describe a how to construct the supergravity solution for a pair of NS5-branes, intersecting on R^{1,3} and localised in all directions except a single transverse circle. Such solutions are rare, and yet may have many potential applications in gauge-gravity duality and model building. The construction invovles developing an explicit map between the conifold metric and the geometry of two intersecting NS5-branes. I will also describe additional intersecting brane solutions corresponding to smoothing out the intersection by, for example, separating branes or putting a metric on the intersection.
Posted by: IC
January 2012
Tue
31 Jan 2012
TBA
Daniel Ricci Pacifici
(Padova)
Wed
25 Jan 2012
Permutation groups, mock theta functions, and K3 surfaces
Jeff Harvey
(Chicago U.)
Abstract:
I will review the connection between the elliptic genus of K3 surfaces and the representation theory of the Mathieu group M_{24} and then discuss a proposed extension of this connection that applies to a larger set of groups and Jacobi forms.
I will review the connection between the elliptic genus of K3 surfaces and the representation theory of the Mathieu group M_{24} and then discuss a proposed extension of this connection that applies to a larger set of groups and Jacobi forms.
Posted by: IC
Wed
25 Jan 2012
Algorithmic String Geometry
Lara Anderson
(Harvard)
Tue
24 Jan 2012
Homogeneous supergravity backgrounds
Jose Figueroa-O'Farrill
(Edinburgh)
Abstract:
We've known since childhood that symmetry can be a very powerful tool in solving partial differential equations. With a little symmetry, one can reduce the number of independent variables, whereas with some more symmetry one can usually separate variables and reduce the problem to solving ordinary differential equations. Given enough symmetry, though, partial differential equations become algebraic. A large body of current research in our field requires finding solutions to the (super)gravity field equations and in this talk I will motivate the search for homogeneous supergravity backgrounds and mention some recent results in this area.
We've known since childhood that symmetry can be a very powerful tool in solving partial differential equations. With a little symmetry, one can reduce the number of independent variables, whereas with some more symmetry one can usually separate variables and reduce the problem to solving ordinary differential equations. Given enough symmetry, though, partial differential equations become algebraic. A large body of current research in our field requires finding solutions to the (super)gravity field equations and in this talk I will motivate the search for homogeneous supergravity backgrounds and mention some recent results in this area.
Posted by: IC
Tue
24 Jan 2012
Ricci solitons
Andrew Dancer
(Oxford)
Abstract:
A Ricci soliton is a generalisation of an Einstein metric which
evolves in a very simple way under the Ricci flow. We discuss ways of
producing examples of Ricci solitons by looking for solutions with a high
degree of symmetry
A Ricci soliton is a generalisation of an Einstein metric which
evolves in a very simple way under the Ricci flow. We discuss ways of
producing examples of Ricci solitons by looking for solutions with a high
degree of symmetry
Posted by: KCL
Wed
18 Jan 2012
The ABCDEFG of Instantons and W-algebras
📍 London
Christoph Keller
(Caltech)
Abstract:
For arbitrary gauge groups, I will describe how one can check
at the one-instanton level that the Nekrasov partition function of
pure N=2 super Yang-Mills is equal to the norm of a certain coherent
state of the corresponding W-algebra. For non-simply-laced gauge
groups, this coherent state is in the twisted sector of a simply-laced
W-algebra. I will also talk about the case of gauge theories with
hypermultiplets.
For arbitrary gauge groups, I will describe how one can check
at the one-instanton level that the Nekrasov partition function of
pure N=2 super Yang-Mills is equal to the norm of a certain coherent
state of the corresponding W-algebra. For non-simply-laced gauge
groups, this coherent state is in the twisted sector of a simply-laced
W-algebra. I will also talk about the case of gauge theories with
hypermultiplets.
Posted by: KCL
Wed
18 Jan 2012
F-Theory, Seiberg-Witten Curves and N = 2 Dualities
Jihye Seo
(McGill U.)
Wed
11 Jan 2012
Towards the proof of AGT-W relation: Toda 3-point function and W(1+infinity) algebra
Shotaro Shiba
(KEK, Tsukuba)