Triangle Seminars
December 2012
Fri
14 Dec 2012
TBA
📍 London
Marcos Marino
(Geneva)
Thu
13 Dec 2012
Quantum gravity at one-loop and AdS/CFT
Marcos Marino
(Geneva U)
Abstract:
Abstract: In the AdS/CFT correspondence, gauge theory calculations beyond the planar approximation correspond to quantum corrections in gravity or in string theory. Recently, the partition function on the three-sphere of Chern-Simons-matter theories has been computed at all orders in the 1/N expansion, and this leads to predictions for quantum corrections in M-theory/string theory. Using the ideas of effective field theory, we show that some of these corrections can be calculated reliably by doing one-loop calculations in supergravity. A similar reasoning has been used recently to calculate logarithmic corrections to black hole entropy, and we use it here to perform a successful test of AdS_4/CFT_3 beyond the leading, planar approximation.
Abstract: In the AdS/CFT correspondence, gauge theory calculations beyond the planar approximation correspond to quantum corrections in gravity or in string theory. Recently, the partition function on the three-sphere of Chern-Simons-matter theories has been computed at all orders in the 1/N expansion, and this leads to predictions for quantum corrections in M-theory/string theory. Using the ideas of effective field theory, we show that some of these corrections can be calculated reliably by doing one-loop calculations in supergravity. A similar reasoning has been used recently to calculate logarithmic corrections to black hole entropy, and we use it here to perform a successful test of AdS_4/CFT_3 beyond the leading, planar approximation.
Posted by: QMW
Wed
12 Dec 2012
Quiver gauge theories and quantum integrable systems
📍 London
Nick Dorey
(DAMTP Cambridge)
Wed
12 Dec 2012
Quantum gravity at one-loop and AdS/CFT
Marcos Marino
(Geneva U.)
Abstract:
In the AdS/CFT correspondence, gauge theory calculations
beyond the planar approximation correspond to quantum corrections in gravity or in string theory.
Recently, the partition function on the three-sphere of Chern-Simons-matter theories has been computed at all orders in the 1/N expansion, and this leads to predictions for quantum corrections in M-theory/string theory. Using the ideas of effective field theory, we show that some of these corrections can be calculated reliably by doing one-loop calculations in supergravity. A similar reasoning has been used recently to calculate logarithmic corrections to black hole entropy, and we use it here to perform a successful test of AdS_4/CFT_3 beyond the leading, planar approximation.
In the AdS/CFT correspondence, gauge theory calculations
beyond the planar approximation correspond to quantum corrections in gravity or in string theory.
Recently, the partition function on the three-sphere of Chern-Simons-matter theories has been computed at all orders in the 1/N expansion, and this leads to predictions for quantum corrections in M-theory/string theory. Using the ideas of effective field theory, we show that some of these corrections can be calculated reliably by doing one-loop calculations in supergravity. A similar reasoning has been used recently to calculate logarithmic corrections to black hole entropy, and we use it here to perform a successful test of AdS_4/CFT_3 beyond the leading, planar approximation.
Posted by: IC
Tue
11 Dec 2012
t.b.a.
Anne Kandler
(City)
Wed
5 Dec 2012
AdS/Ricci-flat correspondence
📍 London
Kostas Skenderis
(Southampton)
Abstract:
We show that for every asymptotically AdS solution compactified on a torus there is a corresponding Ricci-flat solution obtained by replacing the torus by a sphere, performing a Weyl rescaling of the metric and appropriately analytically continuing the dimension of the torus/sphere (as in generalized dimensional reduction). This correspondence should allow us to develop a holographic dictionary for Ricci-flat spacetimes. In particular, it maps Minkowski spacetime to AdS on a torus, the holographic stress energy tensor of AdS to the stress energy tensor due to a brane localized in the interior of spacetime and AdS black branes to (asymptotically flat) Schwarzschild black branes. Applying it to the known solutions describing the hydrodynamic regime in AdS/CFT, we compute the dispersion relation of the Gregory-Laflamme unstable modes through cubic order in the wavenumber, finding remarkable agreement with numerical data. We further obtain the fluid dual to Rindler spacetime and show that its transport coefficients through second order follow from the AdS ones.
We show that for every asymptotically AdS solution compactified on a torus there is a corresponding Ricci-flat solution obtained by replacing the torus by a sphere, performing a Weyl rescaling of the metric and appropriately analytically continuing the dimension of the torus/sphere (as in generalized dimensional reduction). This correspondence should allow us to develop a holographic dictionary for Ricci-flat spacetimes. In particular, it maps Minkowski spacetime to AdS on a torus, the holographic stress energy tensor of AdS to the stress energy tensor due to a brane localized in the interior of spacetime and AdS black branes to (asymptotically flat) Schwarzschild black branes. Applying it to the known solutions describing the hydrodynamic regime in AdS/CFT, we compute the dispersion relation of the Gregory-Laflamme unstable modes through cubic order in the wavenumber, finding remarkable agreement with numerical data. We further obtain the fluid dual to Rindler spacetime and show that its transport coefficients through second order follow from the AdS ones.
Posted by: KCL
Wed
5 Dec 2012
Curved geometries for rigid supersymmetry
Davide Cassani
(King's College)
Abstract:
Supersymmetry on curved spaces has recently attracted much attention, mainly as a tool towards the exact computation of quantum field theory observables via localization. Taking a holographic perspective, I will discuss how the conditions for rigid supersymmetry to be preserved on a curved boundary arise from the bulk supergravity Killing spinor equations. In particular, I will show that a four-dimensional superconformal field theory can be put on a curved, Lorentzian spacetime if and only if this admits a null conformal Killing vector. For a supersymmetric field theory with an R-symmetry, not necessarily conformal, the vector is further restricted to be Killing. After having presented some illustrative examples, I will conclude comparing with the Euclidean case.
Supersymmetry on curved spaces has recently attracted much attention, mainly as a tool towards the exact computation of quantum field theory observables via localization. Taking a holographic perspective, I will discuss how the conditions for rigid supersymmetry to be preserved on a curved boundary arise from the bulk supergravity Killing spinor equations. In particular, I will show that a four-dimensional superconformal field theory can be put on a curved, Lorentzian spacetime if and only if this admits a null conformal Killing vector. For a supersymmetric field theory with an R-symmetry, not necessarily conformal, the vector is further restricted to be Killing. After having presented some illustrative examples, I will conclude comparing with the Euclidean case.
Posted by: IC
Tue
4 Dec 2012
t.b.a.
Nick Dorey
(DAMTP)
Mon
3 Dec 2012
Higher-spin cubic interactions and holography
Euihun Joung
(SNS, Pisa)
Abstract:
Some issues of higher-spin (HS) gauge theory (in d+1>3) related to its cubic interactions and holography are discussed. After providing a very brief overview on the topic, I show how to construct all gauge consistent cubic interactions using the ambient-space formulation. Its number matches that of all possible 3pt functions, recently derived by other groups. However only one vertex corresponds to the free scalar CFT on the boundary, hence the metric-like version of the vertex encoded in Vasiliev's equation.
Some issues of higher-spin (HS) gauge theory (in d+1>3) related to its cubic interactions and holography are discussed. After providing a very brief overview on the topic, I show how to construct all gauge consistent cubic interactions using the ambient-space formulation. Its number matches that of all possible 3pt functions, recently derived by other groups. However only one vertex corresponds to the free scalar CFT on the boundary, hence the metric-like version of the vertex encoded in Vasiliev's equation.
Posted by: IC
Sun
2 Dec 2012
Quantum mechanical models, cellular automata and a discrete action principle
Thomas Elze
(Pisa University)
Abstract:
It will be shown that the dynamics of discrete (integer-valued) Hamiltonian cellular automata can only be consistently defined, if it is linear in the same sense that unitary evolution in quantum mechanics is linear. This suggests us to look for an invertible map between such automata and continuous quantum mechanical models. Based on sampling theory, such a map can indeed be constructed and leads to quantum mechanical models which incorporate a fundamental scale. The admissible observables, the one-to-one correspondence of the respective conservation laws, and the existence of solutions of the modified dispersion relation for stationary states are discussed.
References:
H.-T. Elze, Action principle for cellular automata and the linearity of quantum mechanics, Phys. Rev. A 89, 012111 (2014) [arXiv:1312.1615];
do., Journal of Physics: Conference Series 504 (2014) 012004 [arXiv:1403.2646].
It will be shown that the dynamics of discrete (integer-valued) Hamiltonian cellular automata can only be consistently defined, if it is linear in the same sense that unitary evolution in quantum mechanics is linear. This suggests us to look for an invertible map between such automata and continuous quantum mechanical models. Based on sampling theory, such a map can indeed be constructed and leads to quantum mechanical models which incorporate a fundamental scale. The admissible observables, the one-to-one correspondence of the respective conservation laws, and the existence of solutions of the modified dispersion relation for stationary states are discussed.
References:
H.-T. Elze, Action principle for cellular automata and the linearity of quantum mechanics, Phys. Rev. A 89, 012111 (2014) [arXiv:1312.1615];
do., Journal of Physics: Conference Series 504 (2014) 012004 [arXiv:1403.2646].
Posted by: IC
November 2012
Wed
28 Nov 2012
Prospects of Supersymmetry at the LHC: Recent LHC Results
📍 London
Ben Allanach
(Cambridge, DAMTP)
Abstract:
I will summarise the Higgs search results and searches for supersymmetric particles from the LHC, commenting on the
recent evidence found for rare decays of the Bs meson into mu+ mu-. I shall comment on what the Higgs means for the
discovery prospects for supersymmetry.
I will summarise the Higgs search results and searches for supersymmetric particles from the LHC, commenting on the
recent evidence found for rare decays of the Bs meson into mu+ mu-. I shall comment on what the Higgs means for the
discovery prospects for supersymmetry.
Posted by: KCL
Wed
28 Nov 2012
Prospects of Supersymmetry at the LHC: Why Should we believe in Supersymmetry?
📍 London
Matt Dolan
(Durham)
Abstract:
I will summarise why SUSY may be a good idea phenomenologically, and what
theoretical and phenomenological problems it can solve for us. I'll argue
that there's more to life than the CMSSM, and discuss what we might learn
from the continuing absence of BSM signals at the LHC.
I will summarise why SUSY may be a good idea phenomenologically, and what
theoretical and phenomenological problems it can solve for us. I'll argue
that there's more to life than the CMSSM, and discuss what we might learn
from the continuing absence of BSM signals at the LHC.
Posted by: KCL
Tue
27 Nov 2012
Sums, Restricted Sums and Differences
David Penman
(Essex)
Abstract:
Given a (nonempty) set \(A\) of integers, two of the most obvious things to do with it are to form the sumset \(A+A=\{a+b:\,a,b\in A\}\) and the difference set \(A-A=\{a-b:\,a,b\in A\}\). One might also wish to consider the restricted sumset \(A\hat{+}A=\{a+b:\,a,b\in A,\,a\neq b\}\). One can then ask various obvious questions about the relationships between the sizes of various of these sets and what this implies about structure, and I shall discuss some known results on this, including generalisations to more general contexts, e.g. in group theory. An intuition one might have is that the sumset/restricted sumset will be smaller than the difference set as addition is commutative but subtraction isn't: I shall survey various known results showing that this intuition is non-trivially wrong. At the end I shall discuss some recent constructions of sets \(A\) which give new record large values of \(\log(|A+A|)/\log(|A-A|)\). The original part of the talk is based on joint work with my research student Matthew Wells.
Given a (nonempty) set \(A\) of integers, two of the most obvious things to do with it are to form the sumset \(A+A=\{a+b:\,a,b\in A\}\) and the difference set \(A-A=\{a-b:\,a,b\in A\}\). One might also wish to consider the restricted sumset \(A\hat{+}A=\{a+b:\,a,b\in A,\,a\neq b\}\). One can then ask various obvious questions about the relationships between the sizes of various of these sets and what this implies about structure, and I shall discuss some known results on this, including generalisations to more general contexts, e.g. in group theory. An intuition one might have is that the sumset/restricted sumset will be smaller than the difference set as addition is commutative but subtraction isn't: I shall survey various known results showing that this intuition is non-trivially wrong. At the end I shall discuss some recent constructions of sets \(A\) which give new record large values of \(\log(|A+A|)/\log(|A-A|)\). The original part of the talk is based on joint work with my research student Matthew Wells.
Posted by: KCL
Thu
22 Nov 2012
TBA
Michael Green
(Cambridge)
Wed
21 Nov 2012
The Heterotic counterpart of D-brane recombination
📍 London
Massimo Bianchi
(Roma Tor Vergata and Imperial)
Tue
20 Nov 2012
WZW term in Permutation Cosets
Alessandra Cagnazzo
(Nordita)
Abstract:
The study of Superstring Theories on AdS backgrounds is important in the context of Gauge/Gravity correspondence. These theories can be reduced, under certain assumptions,
to Sigma Models on semi-symmetric super-cosets. For a peculiar class of these cosets one can also introduce a WZW term. This correspond to study a Superstring Theory
on a background supported by a mixture of RR and NSNS fluxes, as can happen for theories on \(AdS_3\times S^3 \times M_4\).
I will show the effect of this term on Integrability, Kappa symmetry and conformality of the theory, computing also the BMN spectrum in some relevant case for \(AdS_3/CFT_2\) correspondence.
The study of Superstring Theories on AdS backgrounds is important in the context of Gauge/Gravity correspondence. These theories can be reduced, under certain assumptions,
to Sigma Models on semi-symmetric super-cosets. For a peculiar class of these cosets one can also introduce a WZW term. This correspond to study a Superstring Theory
on a background supported by a mixture of RR and NSNS fluxes, as can happen for theories on \(AdS_3\times S^3 \times M_4\).
I will show the effect of this term on Integrability, Kappa symmetry and conformality of the theory, computing also the BMN spectrum in some relevant case for \(AdS_3/CFT_2\) correspondence.
Posted by: IC
Tue
20 Nov 2012
C A N C E L L E D
Gerard Watts
(King's)
Thu
15 Nov 2012
TBA
Anupam Mazumdar
(Lancaster)
Wed
14 Nov 2012
On four-point function of conserved currents in a general CFT
📍 London
Anatoly Dymarsky
(DAMTP Cambridge)
Abstract:
I will discuss the ongoing effort to constrain the four-point function of conserved spin 1 and 2 currents tensors in a general conformal field theories in d>3 by applying the full set of the corresponding Ward identities.
I will discuss the ongoing effort to constrain the four-point function of conserved spin 1 and 2 currents tensors in a general conformal field theories in d>3 by applying the full set of the corresponding Ward identities.
Posted by: KCL
Wed
14 Nov 2012
Wall-crossing, multi-centered black holes and quivers
Boris Pioline
(LPTHE Jussieu and CERN)
Abstract:
BPS states in N=2 gauge theories or string vacua are generically stable but liable to decay across certain codimension-one loci in moduli space. This process is easily understood by viewing BPS states as a bound state of more elementary BPS constituents, described classically by multi-centered solutions of the low energy effective action. The semi-classical quantization of the space of such solutions agrees with the wall-crossing formulae derived in the mathematical literature on BPS invariants, providing a physically elementary justification of the latter. Using this intuition, it is possible to express the BPS index, at any point in moduli space, in terms of indices associated to elementary (or single-centered) constituents. If time permits, I will present evidence for this idea in the case of BPS states described by quiver representations.
BPS states in N=2 gauge theories or string vacua are generically stable but liable to decay across certain codimension-one loci in moduli space. This process is easily understood by viewing BPS states as a bound state of more elementary BPS constituents, described classically by multi-centered solutions of the low energy effective action. The semi-classical quantization of the space of such solutions agrees with the wall-crossing formulae derived in the mathematical literature on BPS invariants, providing a physically elementary justification of the latter. Using this intuition, it is possible to express the BPS index, at any point in moduli space, in terms of indices associated to elementary (or single-centered) constituents. If time permits, I will present evidence for this idea in the case of BPS states described by quiver representations.
Posted by: IC
Tue
13 Nov 2012
t.b.a.
Tina Davies
(Leeds)
Wed
7 Nov 2012
On Singular Fibres in F-Theory
📍 London
Andreas Braun
(King's College)
Abstract:
In compactifications of M-Theory, certain singularities are expected to give rise to non-abelian gauge theories. In case the compactification manifold admits an torus fibration, such singularities become degenerations of the fibre. In this framework (which is called F-Theory), the behaviour of the fibre is well-understood for elliptic surfaces, but there remain puzzles both from the perspective of mathematics and physics in higher dimensions. After an introduction, I will report on some recent progress on the interplay of the structure of degenerate fibres and the effective field theory description.
In compactifications of M-Theory, certain singularities are expected to give rise to non-abelian gauge theories. In case the compactification manifold admits an torus fibration, such singularities become degenerations of the fibre. In this framework (which is called F-Theory), the behaviour of the fibre is well-understood for elliptic surfaces, but there remain puzzles both from the perspective of mathematics and physics in higher dimensions. After an introduction, I will report on some recent progress on the interplay of the structure of degenerate fibres and the effective field theory description.
Posted by: KCL
Wed
7 Nov 2012
The AdS5xS5 string spectrum, Pohlmeyer reduction and quantum deformations
Stijn van Tongeren
(ITP and Spinoza Inst., Utrecht)
Abstract:
In the setting of integrability in AdS/CFT, in the typical approach to the AdS_5 x S^5 string a light-cone gauge is fixed, breaking Lorentz invariance on the worldsheet. One attempt to avoid the need for this goes under the name of Pohlmeyer reduction. Recently an S-matrix was conjectured to describe the scattering of solitons in this theory. Now as I will explain in my talk, the S-matrix of an integrable quantum field theory together with its dispersion relation are enough to find its finite volume spectrum exactly, through the so-called thermodynamic Bethe ansatz. I will work this out for an S-matrix and dispersion that interpolate between the standard light-cone gauge fixed superstring and this conjectured Pohlmeyer S-matrix, by analogy to a simpler model. Viewed as a deformation of the light-cone gauge fixed superstring TBA, this story is very similar to deforming the XXX spin chain to the XXZ one, which I will concretely discuss. I will finish by emphasizing important differences to this simple toy model, and discuss surprises in the so-called Y-system associated to the TBA equations.
In the setting of integrability in AdS/CFT, in the typical approach to the AdS_5 x S^5 string a light-cone gauge is fixed, breaking Lorentz invariance on the worldsheet. One attempt to avoid the need for this goes under the name of Pohlmeyer reduction. Recently an S-matrix was conjectured to describe the scattering of solitons in this theory. Now as I will explain in my talk, the S-matrix of an integrable quantum field theory together with its dispersion relation are enough to find its finite volume spectrum exactly, through the so-called thermodynamic Bethe ansatz. I will work this out for an S-matrix and dispersion that interpolate between the standard light-cone gauge fixed superstring and this conjectured Pohlmeyer S-matrix, by analogy to a simpler model. Viewed as a deformation of the light-cone gauge fixed superstring TBA, this story is very similar to deforming the XXX spin chain to the XXZ one, which I will concretely discuss. I will finish by emphasizing important differences to this simple toy model, and discuss surprises in the so-called Y-system associated to the TBA equations.
Posted by: IC
Thu
1 Nov 2012
TBA
Sebastian Franco
(Durham)
October 2012
Wed
31 Oct 2012
Generalised geometry and supergravity
📍 London
Daniel Waldram
(Imperial College)
Abstract:
We show how "generalised geometry", a class of extensions of conventional
differential geometry first introduced by Hitchin, gives a natural way of
formulating supergravity theories. The formulation unifies the bosonic
fields and symmetries and has a natural action of O(d,d) or the exceptional
groups E_d in d-dimensions. By introducing the analogue of the Levi-Civita
connection we find that full set of bosonic equations of motion reduce to
simply the vanishing of the generalised Ricci tensor. We show that the
connection also encodes the supersymmetry variations and fermionic equations
of motion.
This formalism also gives natural extensions of complex, symplectic and
other integrable structures, with implications for describing supersymmetric
string theory backgrounds.
We show how "generalised geometry", a class of extensions of conventional
differential geometry first introduced by Hitchin, gives a natural way of
formulating supergravity theories. The formulation unifies the bosonic
fields and symmetries and has a natural action of O(d,d) or the exceptional
groups E_d in d-dimensions. By introducing the analogue of the Levi-Civita
connection we find that full set of bosonic equations of motion reduce to
simply the vanishing of the generalised Ricci tensor. We show that the
connection also encodes the supersymmetry variations and fermionic equations
of motion.
This formalism also gives natural extensions of complex, symplectic and
other integrable structures, with implications for describing supersymmetric
string theory backgrounds.
Posted by: KCL
Wed
31 Oct 2012
Anomalous Transport from Kubo Formulae
Karl Landsteiner
(IFT, UAM)
Abstract:
Chiral anomalies have profound impact on the transport properties of relativistic fluids. They are closely related to the creation of currents by magnetic fields or vortices in the fluid via the so called Chiral Magnetic Conductivity and the Chiral Vortical Conductivity. Both can be computed by Kubo type formulae from special kinematic limits of two point functions of currents. I will review the calculation of these conductivites in a gas of free Weyl fermions and at strong coupling via a holographic model. A special and somewhat mysterious role is played by the mixed gauge-gravitational anomaly.
Chiral anomalies have profound impact on the transport properties of relativistic fluids. They are closely related to the creation of currents by magnetic fields or vortices in the fluid via the so called Chiral Magnetic Conductivity and the Chiral Vortical Conductivity. Both can be computed by Kubo type formulae from special kinematic limits of two point functions of currents. I will review the calculation of these conductivites in a gas of free Weyl fermions and at strong coupling via a holographic model. A special and somewhat mysterious role is played by the mixed gauge-gravitational anomaly.
Posted by: IC
Wed
31 Oct 2012
t.b.a.
Tamara Rogers
(Arizona)
Tue
30 Oct 2012
t.b.a.
Jerome Gauntlett
(Imperial)
Wed
24 Oct 2012
Towards a taxonomy of extremal black brane geometries
Shamit Kachru
(Stanford and SLAC)
Wed
24 Oct 2012
Some remarks on non-Fermi liquids in field theory and holography
Shamit Kachru
(Stanford and SLAC)
Tue
23 Oct 2012
t.b.a.
Andrey Morozov
(Leicester)
Mon
22 Oct 2012
Holography of 3d N=4 superconformal quiver theories
John Estes
(Imperial College)
Abstract:
3d N=4 superconformal quiver theories arise as the low energy description of intersecting D3/D5/NS5 branes. I will discuss the backreacted solutions describing the near horizon geometry of such configurations. A map between the CFT and supergravity solutions is proposed. As a check, the CFT partition function on S^3 is computed using localization technqiues and matched to the supergravity results.
3d N=4 superconformal quiver theories arise as the low energy description of intersecting D3/D5/NS5 branes. I will discuss the backreacted solutions describing the near horizon geometry of such configurations. A map between the CFT and supergravity solutions is proposed. As a check, the CFT partition function on S^3 is computed using localization technqiues and matched to the supergravity results.
Posted by: IC
Fri
19 Oct 2012
A Modern look at the Regge limit in QCD, SUSY and gravity
Agustin Sabio Vera
(Universidad Autonoma de Madrid / CERN)
Abstract:
A pedagogical introduction to the Regge limit of scattering amplitudes
will be given. Its role in collider physics will be explained, together
with its connections to integrability in QCD and SUSY theories. We will
finish with a discussion on graviton scattering at high energies.
A pedagogical introduction to the Regge limit of scattering amplitudes
will be given. Its role in collider physics will be explained, together
with its connections to integrability in QCD and SUSY theories. We will
finish with a discussion on graviton scattering at high energies.
Posted by: QMW
Thu
18 Oct 2012
On Non-Abelian T-Dualities and AdS Geometries
Daniel Thompson
(Solvay Institutes)
Abstract:
I will explain how the notion of T-duality can be generalised to
the case of a non-abelian isometry group and applied as a solution
generating symmetry to type II supergravity backgrounds involving RR flux.
I will show some novel mappings between IIB and (massive) IIA supergravity
and apply the technique to backgrounds of importance in the context of the
gauge/gravity correspondence. In particular we will find some surprising
connections between \(AdS_5\times S^5\) and the geometry proposed by Gaiotto
and Maldacena as dual to certain N=2 SCFT's and between the Klebanov-Witten
background (\(AdS_5 \times T^{1,1}\)) and the geometries discussed already in
this seminar series by Wecht as dual to certain N=1 SCFT's. Time
permitting I will describe some recent developments relating to the gravity
duals of cascading gauge theories.
I will explain how the notion of T-duality can be generalised to
the case of a non-abelian isometry group and applied as a solution
generating symmetry to type II supergravity backgrounds involving RR flux.
I will show some novel mappings between IIB and (massive) IIA supergravity
and apply the technique to backgrounds of importance in the context of the
gauge/gravity correspondence. In particular we will find some surprising
connections between \(AdS_5\times S^5\) and the geometry proposed by Gaiotto
and Maldacena as dual to certain N=2 SCFT's and between the Klebanov-Witten
background (\(AdS_5 \times T^{1,1}\)) and the geometries discussed already in
this seminar series by Wecht as dual to certain N=1 SCFT's. Time
permitting I will describe some recent developments relating to the gravity
duals of cascading gauge theories.
Posted by: QMW
Wed
17 Oct 2012
Rigid supersymmetry on Three-Manifolds
📍 London
Cyril Closset
(Weizmann Institute)
Abstract:
I will explain how to put three-dimensional supersymmetric theories on curved three-manifolds preserving some supersymmetry. I will discuss some physical implications of this method, including an exact formula for the two-point function of the energy-momentum tensor in 3d N=2 superconformal theories.
I will explain how to put three-dimensional supersymmetric theories on curved three-manifolds preserving some supersymmetry. I will discuss some physical implications of this method, including an exact formula for the two-point function of the energy-momentum tensor in 3d N=2 superconformal theories.
Posted by: KCL
Wed
17 Oct 2012
Holomorphic Blocks in Three Dimensions
Sara Pasquetti
(Surrey)
Tue
16 Oct 2012
t.b.a.
Marcus Linkelmann
(City)
Thu
11 Oct 2012
Gravity tree amplitudes and twistor-string theory
Lionel Mason
(Oxford)
Abstract:
We use an observation of Maldacena to argue that gravity tree-amplitudes can be computed
by inserting appropriate wave-functions into the Witten-Berkovits twistor-string for
conformal gravity. This is used to motivate and partially explain the recent remarkable
twistor-string-like formula of Cachazo & Skinner that expresses the complete tree-level
S-matrix for N=8 supergravity in terms of an integral over rational curves in twistor
space.
We use an observation of Maldacena to argue that gravity tree-amplitudes can be computed
by inserting appropriate wave-functions into the Witten-Berkovits twistor-string for
conformal gravity. This is used to motivate and partially explain the recent remarkable
twistor-string-like formula of Cachazo & Skinner that expresses the complete tree-level
S-matrix for N=8 supergravity in terms of an integral over rational curves in twistor
space.
Posted by: QMW
Wed
10 Oct 2012
New SCFTs From M5-Branes
📍 London
Brian Wecht
(Queen Mary)
Abstract:
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
Posted by: KCL
Wed
10 Oct 2012
Minimal Area Surfaces and Wilson Loops
Martin Kruczenski
(Purdue)
Abstract:
The AdS/CFT correspondence has recently allowed the computation of gauge theory quantities in the strong coupled regime (for certain particular theories). One important such quantity is the Wilson loop which is related to the quark/ anti-quark potential, scattering amplitudes, etc. The computation is reduced to finding minimal area surfaces in hyperbolic space. Although this is a classical problem in mathematics its solution is not easy since it involves non-linear partial differential equations. In this talk I will describe some recent work where we found an infinite parameter family of such surfaces by using Riemann Theta functions to analytically solve the equations.
The AdS/CFT correspondence has recently allowed the computation of gauge theory quantities in the strong coupled regime (for certain particular theories). One important such quantity is the Wilson loop which is related to the quark/ anti-quark potential, scattering amplitudes, etc. The computation is reduced to finding minimal area surfaces in hyperbolic space. Although this is a classical problem in mathematics its solution is not easy since it involves non-linear partial differential equations. In this talk I will describe some recent work where we found an infinite parameter family of such surfaces by using Riemann Theta functions to analytically solve the equations.
Posted by: IC
Tue
9 Oct 2012
Novel algebraic directions in Free Probability Theory
Roland Friedrich
(Humboldt)
Abstract:
Free probability theory, a species of non-commutative probability theory, is amazing for several reasons. Not only has it nice combinatorial features underlying it but also profound connections with other fields, in particular physics. Recently, we established a priori unexpected relations with some very prominent algebraic objects, in particular Hopf algebras. In this talk we will carefully introduce some of the basic features and give a glance at future directions.
Free probability theory, a species of non-commutative probability theory, is amazing for several reasons. Not only has it nice combinatorial features underlying it but also profound connections with other fields, in particular physics. Recently, we established a priori unexpected relations with some very prominent algebraic objects, in particular Hopf algebras. In this talk we will carefully introduce some of the basic features and give a glance at future directions.
Posted by: KCL
Mon
8 Oct 2012
Localizing the black M2-M5 intersection
Vasilis Niarchos
(Crete U.)
Abstract:
I will discuss recent work on the supergravity description of the fully localized orthogonal black M2-M5 intersection using blackfold theory. Special emphasis will be given to the near-extremal thermodynamics of this system from which we can read off, for the first time, the large-N scaling of the central charge of the two-dimensional superconformal field theory that lives at the intersection. The resulting formula for this central charge is suggestive for the underlying M2 and M5 brane physics.
I will discuss recent work on the supergravity description of the fully localized orthogonal black M2-M5 intersection using blackfold theory. Special emphasis will be given to the near-extremal thermodynamics of this system from which we can read off, for the first time, the large-N scaling of the central charge of the two-dimensional superconformal field theory that lives at the intersection. The resulting formula for this central charge is suggestive for the underlying M2 and M5 brane physics.
Posted by: IC
Fri
5 Oct 2012
On the Large N Limit of Chern-Simons Theories with Fundamental Matter and Three Dimensional Bosonization
Ran Yacoby
(Weizmann)
Abstract:
I will review the recent progress in the study of three dimensional U(N)_k Chern-Simons theories coupled to a massless boson or fermion in the fundamental representation. In particular, in the planar limit, one can determine the conformal fixed points and spectrum of local primary operators of these theories. In addition, the planar 3-point functions can be computed exactly as a function of the 't Hooft coupling, and the results agree with the general predictions of Maldacena and Zhiboedov for the correlators of theories that have high-spin symmetries in the large N limit. It has been suggested in the past that the fermionic and bosonic theories are dual to each other at large N. Using the exact expressions of the planar 3-point functions, one can find the precise mapping between the two theories. In particular, it was found that the theory of N scalars coupled to a U(N)_k Chern-Simons theory is equivalent to the Gross-Neveu model of k fermions coupled to a U(k)_N Chern-Simons theory, thus providing a bosonization of the latter theory.
I will review the recent progress in the study of three dimensional U(N)_k Chern-Simons theories coupled to a massless boson or fermion in the fundamental representation. In particular, in the planar limit, one can determine the conformal fixed points and spectrum of local primary operators of these theories. In addition, the planar 3-point functions can be computed exactly as a function of the 't Hooft coupling, and the results agree with the general predictions of Maldacena and Zhiboedov for the correlators of theories that have high-spin symmetries in the large N limit. It has been suggested in the past that the fermionic and bosonic theories are dual to each other at large N. Using the exact expressions of the planar 3-point functions, one can find the precise mapping between the two theories. In particular, it was found that the theory of N scalars coupled to a U(N)_k Chern-Simons theory is equivalent to the Gross-Neveu model of k fermions coupled to a U(k)_N Chern-Simons theory, thus providing a bosonization of the latter theory.
Posted by: IC
Thu
4 Oct 2012
New SCFTs From M5-Branes I
Brian Wecht
(Queen Mary)
Abstract:
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
Posted by: QMW
Wed
3 Oct 2012
Spherical partition functions of N = (2, 2) gauge theories and vortices
📍 London
Stefano Cremonesi
(Imperial College)
Abstract:
I will review the localisation of 2d N = (2, 2) supersymmetric gauge
theories with a vector U(1) R-symmetry on the round 2-sphere, leading to
a matrix integral expression for the partition function, in the so
called "Coulomb branch" representation. For gauge theories which are
completely Higgsed in the presence of a Fayet-Iliopoulos term, an
alternative localization scheme yields the "Higgs branch" representation
of the same partition function as the product of vortex times antivortex
partition functions, weighted by semiclassical factors and summed over
isolated vacua on the Higgs branch. Finally, I will briefly overview the
potential of these exact results for the study of type II string
compactifications and supersymmetric gauge theories in various
dimensions. Based on arXiv:1206.2356 with F. Benini.
I will review the localisation of 2d N = (2, 2) supersymmetric gauge
theories with a vector U(1) R-symmetry on the round 2-sphere, leading to
a matrix integral expression for the partition function, in the so
called "Coulomb branch" representation. For gauge theories which are
completely Higgsed in the presence of a Fayet-Iliopoulos term, an
alternative localization scheme yields the "Higgs branch" representation
of the same partition function as the product of vortex times antivortex
partition functions, weighted by semiclassical factors and summed over
isolated vacua on the Higgs branch. Finally, I will briefly overview the
potential of these exact results for the study of type II string
compactifications and supersymmetric gauge theories in various
dimensions. Based on arXiv:1206.2356 with F. Benini.
Posted by: KCL
Wed
3 Oct 2012
The ABCDEFG of Instantons
Jaewon Song
(UCSD)
Abstract:
We will discuss methods of computing instanton partition functions for arbitrary gauge groups including the exceptional ones. Even though there is no explicit algebraic construction of instanton moduli space available for the EFG groups beyond 1-instanton, we're able to evaluate the partition function using the blow-up recursion relations derived by Nakajima and Yoshioka. We compare this result with the recent proposal based on the superconformal index of SCFTs with E6, E7 global symmetry. We also compare our result with the norm of certain coherent states of W-algebras and thereby extending the AGT correspondence for pure YM theory to all gauge groups.
Reference: 1111.5624, 1205.4722.
We will discuss methods of computing instanton partition functions for arbitrary gauge groups including the exceptional ones. Even though there is no explicit algebraic construction of instanton moduli space available for the EFG groups beyond 1-instanton, we're able to evaluate the partition function using the blow-up recursion relations derived by Nakajima and Yoshioka. We compare this result with the recent proposal based on the superconformal index of SCFTs with E6, E7 global symmetry. We also compare our result with the norm of certain coherent states of W-algebras and thereby extending the AGT correspondence for pure YM theory to all gauge groups.
Reference: 1111.5624, 1205.4722.
Posted by: IC
Wed
3 Oct 2012
New SCFTs From M5-Branes II
Brian Wecht
(Queen Mary)
Abstract:
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
I will describe a new infinite set of AdS/CFT dual pairs which come from M5-branes wrapping Riemann surfaces. These solutions interpolate between and extend beyond a famous pair of solutions by Maldacena and Nunez. Additionally, the dual SCFTs are so-called "non-Lagrangian" theories, which have no weakly coupled UV description yet can (and will) be described explicitly.
Posted by: QMW
September 2012
Thu
27 Sep 2012
Seiberg-Witten geometry of N=2 quiver theories, and quantization
Nikita Nekrasov
(IHES)
Thu
27 Sep 2012
Three-point functions from two point functions
Konstantin Wiegandt
(Queen Mary)
Abstract:
The blackboard-talk will consist of an introductory part on two and three-point functions and their relation to the operator product expansion. In particular I will talk about "twist two operators" in N=4 SYM and other conformal theories and explain how you can calculate the structure constants of these three-point functions by only calculating two-point functions, and as a side effect also avoiding the need of information on the one-loop mixing matrix.
The blackboard-talk will consist of an introductory part on two and three-point functions and their relation to the operator product expansion. In particular I will talk about "twist two operators" in N=4 SYM and other conformal theories and explain how you can calculate the structure constants of these three-point functions by only calculating two-point functions, and as a side effect also avoiding the need of information on the one-loop mixing matrix.
Posted by: QMW