Triangle Seminars
December 2015
Wed
16 Dec 2015
Effective theories of thermoelectric transport from holography
Blaise Gouteraux
(Stanford)
Abstract:
In this talk, I will summarize recent progress in the description of thermoelectric transport using gauge/gravity duality. I will first review thermoelectric transport in hydrodynamics, where momentum conservation implies infinite zero-frequency conductivities. By a change of basis of the conserved currents, a universal, finite conductivity can be extracted. It can be computed holographically. I will discuss its low-temperature scaling in terms of critical exponents characterizing time and space anisotropy and anomalous dimensions for the free energy and conserved current. When momentum is almost conserved, the zero-frequency delta functions broaden into Drude-like peaks. A holographic computation precisely identifies the redistribution of the low-frequency spectral weight between two contributions originating from the non-conservation of momentum and intrinsic dissipation respectively. It also sheds some light on how to construct effective theories of thermoelectric transport when momentum is not conserved.
In this talk, I will summarize recent progress in the description of thermoelectric transport using gauge/gravity duality. I will first review thermoelectric transport in hydrodynamics, where momentum conservation implies infinite zero-frequency conductivities. By a change of basis of the conserved currents, a universal, finite conductivity can be extracted. It can be computed holographically. I will discuss its low-temperature scaling in terms of critical exponents characterizing time and space anisotropy and anomalous dimensions for the free energy and conserved current. When momentum is almost conserved, the zero-frequency delta functions broaden into Drude-like peaks. A holographic computation precisely identifies the redistribution of the low-frequency spectral weight between two contributions originating from the non-conservation of momentum and intrinsic dissipation respectively. It also sheds some light on how to construct effective theories of thermoelectric transport when momentum is not conserved.
Posted by: IC
Mon
14 Dec 2015
Mechanics of a Volvox Embryo Turning Itself Inside Out
Pierre Haas
(DAMTP)
Abstract:
Deformations of cell sheets are ubiquitous in early animal development, yet they arise from an intricate interplay of cell shape changes, cell migration, cell intercalation, and cell division. We combine theory and experiment to explore what is perhaps the simplest instance of cell sheet folding, the "inversion" process in the green alga Volvox: at the end of cell division, a Volvox embryo consists of several thousand cells arrayed to form a thin spherical sheet, but those cell poles whence will emanate the flagella point into the sphere. In a process hypothesised to arise from cell shape changes alone, the embryos therefore turn themselves inside out to acquire the ability to swim. We have recently acquired the first three-dimensional time-lapse visualisations of this inversion, using light sheet microscopy to reveal the intriguing dynamics of the process. A theoretical model, in which cell shape changes correspond to local variations of intrinsic curvature and stretches of an elastic shell, sheds light on the underlying mechanics of inversion and reproduces the shapes and dynamics of inversion qualitatively.
This is joint work with Stephanie Höhn, Aurelia Honerkamp-Smith, Philipp Khuc Trong and Ray Goldstein.
Deformations of cell sheets are ubiquitous in early animal development, yet they arise from an intricate interplay of cell shape changes, cell migration, cell intercalation, and cell division. We combine theory and experiment to explore what is perhaps the simplest instance of cell sheet folding, the "inversion" process in the green alga Volvox: at the end of cell division, a Volvox embryo consists of several thousand cells arrayed to form a thin spherical sheet, but those cell poles whence will emanate the flagella point into the sphere. In a process hypothesised to arise from cell shape changes alone, the embryos therefore turn themselves inside out to acquire the ability to swim. We have recently acquired the first three-dimensional time-lapse visualisations of this inversion, using light sheet microscopy to reveal the intriguing dynamics of the process. A theoretical model, in which cell shape changes correspond to local variations of intrinsic curvature and stretches of an elastic shell, sheds light on the underlying mechanics of inversion and reproduces the shapes and dynamics of inversion qualitatively.
This is joint work with Stephanie Höhn, Aurelia Honerkamp-Smith, Philipp Khuc Trong and Ray Goldstein.
Posted by: KCL
Mon
14 Dec 2015
Can Molecular Simulations Help us Understand how Nerve Cells in the Brain Communicate?
Carla Molteni
(King's)
Abstract:
Neurotransmitter-gated ion channels are complex neuroreceptors located in the membrane of nerve cells that control the rapid transmission of nerve impulses. Their malfunction is linked to serious neurological disorders, including Alzheimer’s disease, and they are major therapeutic targets; in invertebrates they are involved in insecticide resistance. However, we have little idea of how they function at the molecular level due to their complexity and limited experimental information. In particular it is not clear how the binding of a small molecule (the neurotransmitter) triggers a series of events culminating into the opening (gating) of the transmembrane channel: ions can then flood across the cell membrane modifying the cell activity. State-of-the-art and novel computational techniques are therefore crucial to build an accurate picture at the atomic level of the mechanisms that drive the activation of these ion channels, complementing the available experimental data. We have used a range of simulation techniques, including metadynamics (a method for accelerating rare events and sample free energy landscapes), to explore the mechanisms of neurotransmitter binding and a potential molecular switch for channel gating. As prototypical examples, we have focussed on the insect GABA-activated RDL receptor and on the serotonin-activated 5-HT3 receptor.
Neurotransmitter-gated ion channels are complex neuroreceptors located in the membrane of nerve cells that control the rapid transmission of nerve impulses. Their malfunction is linked to serious neurological disorders, including Alzheimer’s disease, and they are major therapeutic targets; in invertebrates they are involved in insecticide resistance. However, we have little idea of how they function at the molecular level due to their complexity and limited experimental information. In particular it is not clear how the binding of a small molecule (the neurotransmitter) triggers a series of events culminating into the opening (gating) of the transmembrane channel: ions can then flood across the cell membrane modifying the cell activity. State-of-the-art and novel computational techniques are therefore crucial to build an accurate picture at the atomic level of the mechanisms that drive the activation of these ion channels, complementing the available experimental data. We have used a range of simulation techniques, including metadynamics (a method for accelerating rare events and sample free energy landscapes), to explore the mechanisms of neurotransmitter binding and a potential molecular switch for channel gating. As prototypical examples, we have focussed on the insect GABA-activated RDL receptor and on the serotonin-activated 5-HT3 receptor.
Posted by: KCL
Mon
14 Dec 2015
TBA
Johnjoe McFadden
(Surrey)
Thu
10 Dec 2015
Extremal black holes with wiggles
Geoffrey Compere
(ULB)
Abstract:
Symmetries are crucial in physics. Here I will develop the concept
of symplectic symmetry for Einstein gravity, which is an extension
of the concept of asymptotic symmetries. I will then show that the
throat of the extremal Kerr black hole admits symplectic
symmetries, which leads to an infinite number of conserved charges
which form a Virasoro algebra in 4 dimensions and a novel
generalized Virasoro algebra in higher dimensions. I will build
explicitly the geometries that carry these charges, the so-called
"descendants" of the extremal black hole, in the near-horizon region.
Symmetries are crucial in physics. Here I will develop the concept
of symplectic symmetry for Einstein gravity, which is an extension
of the concept of asymptotic symmetries. I will then show that the
throat of the extremal Kerr black hole admits symplectic
symmetries, which leads to an infinite number of conserved charges
which form a Virasoro algebra in 4 dimensions and a novel
generalized Virasoro algebra in higher dimensions. I will build
explicitly the geometries that carry these charges, the so-called
"descendants" of the extremal black hole, in the near-horizon region.
Posted by: QMW
Wed
9 Dec 2015
Gluing hexagons into three point functions
📍 London
Benjamin Basso
(ENS, Paris)
Abstract:
I will present a framework for computing correlators of three single trace operators in planar N=4 SYM theory that uses hexagonal patches as building blocks. This approach allows one to exploit the integrability of the theory and derive all loop predictions for its structure constants.
After presenting the main ideas and results, I will discuss recent perturbative tests and open problems.
I will present a framework for computing correlators of three single trace operators in planar N=4 SYM theory that uses hexagonal patches as building blocks. This approach allows one to exploit the integrability of the theory and derive all loop predictions for its structure constants.
After presenting the main ideas and results, I will discuss recent perturbative tests and open problems.
Posted by: KCL
Wed
9 Dec 2015
Holographic thermo-electric transport properties and strange metals
Andrea Amoretti
(Cambridge)
Abstract:
Gauge/gravity duality can be used to study the transport
properties of strongly interacting systems with no quasi-particles. I
will give an overview of some holographic toy models of states like
this, in which momentum is not conserved and thus the transport of
energy and charge is non-trivial. Specifically I will discuss the
thermoelectric transport properties of these toy models and their
possible relations to the phenomenology of the strange metals.
Gauge/gravity duality can be used to study the transport
properties of strongly interacting systems with no quasi-particles. I
will give an overview of some holographic toy models of states like
this, in which momentum is not conserved and thus the transport of
energy and charge is non-trivial. Specifically I will discuss the
thermoelectric transport properties of these toy models and their
possible relations to the phenomenology of the strange metals.
Posted by: IC
Tue
8 Dec 2015
tba
Nicola Perra
(Greenwich)
Mon
7 Dec 2015
Exact Path Integral for 3D Quantum Gravity
📍 London
Akinori Tanaka
(RIKEN, Wako, JAPAN)
Abstract:
In 2007, it was conjectured by E.Witten that the chiral part of the partition function of 3d pure AdS Einstein gravity in quantum regime coincides with so-called modular J-function, a partition function of certain holomorphic CFT, called "monster CFT" considered by I. B Frenkel, J. Lepowsky and A. Meurman in the context of monstrous moonshine. We tried to calculate the partition function for the 3d pure AdS Einstein gravity directly by utilizing recently developed localization techniques.Based on some plausible assumptions, we arrived at CFT interpretations.For quantum gravity regime which corresponds to c=24, we get J-function.For semiclassical regime which corresponds c>>1, our partition function decomposes to Virasoro characters, and we derive Cardy formula. If possible, I will comment on application to quantum higher spin gravity.This talk is based on 1504.05991 and 1510.02142.
In 2007, it was conjectured by E.Witten that the chiral part of the partition function of 3d pure AdS Einstein gravity in quantum regime coincides with so-called modular J-function, a partition function of certain holomorphic CFT, called "monster CFT" considered by I. B Frenkel, J. Lepowsky and A. Meurman in the context of monstrous moonshine. We tried to calculate the partition function for the 3d pure AdS Einstein gravity directly by utilizing recently developed localization techniques.Based on some plausible assumptions, we arrived at CFT interpretations.For quantum gravity regime which corresponds to c=24, we get J-function.For semiclassical regime which corresponds c>>1, our partition function decomposes to Virasoro characters, and we derive Cardy formula. If possible, I will comment on application to quantum higher spin gravity.This talk is based on 1504.05991 and 1510.02142.
Posted by: KCL
Mon
7 Dec 2015
Student Triangle Gong Show
Gong Show
(IC/KCL/CU/QMUL)
Abstract:
Student Triangles are a chance for PhD students to give talks to their fellow PhD students from the London Universities, without the pressure of presenting in front of academics. For this first student triangle of the year we will be holding a gong show with a series of short whiteboard talks. PhD students can sign up for a gong show slot on
http://doodle.com/poll/ehgri6kz6f6a8cux
Student Triangles are a chance for PhD students to give talks to their fellow PhD students from the London Universities, without the pressure of presenting in front of academics. For this first student triangle of the year we will be holding a gong show with a series of short whiteboard talks. PhD students can sign up for a gong show slot on
http://doodle.com/poll/ehgri6kz6f6a8cux
Posted by: QMW
Wed
2 Dec 2015
Anomalies RG-Flows and the a-Theorem in Six-Dimensions
📍 London
Clay Cordova
(IAS)
Abstract:
I will describe recent progress in computing Weyl anomalies in strongly-coupled six-dimensional field theories. Along the way we will prove an a-theorem quantifying the loss of degrees of freedom along renormalization group flows.
I will describe recent progress in computing Weyl anomalies in strongly-coupled six-dimensional field theories. Along the way we will prove an a-theorem quantifying the loss of degrees of freedom along renormalization group flows.
Posted by: KCL
Tue
1 Dec 2015
What is computational algebraic geometry in systems biology?
Heather Harrington
(Oxford)
Abstract:
Systems biology aims to understand the molecular interactions that
turn genes on/off, ultimately regulating cellular decisions. These
interactions may be described by a mathematical model that is a
polynomial dynamical system. Generally these interactions are unknown,
leading to multiple models; therefore it is desirable to compare
models with experimental data (e.g., steady-state concentrations of
proteins). Often model parameter values are unknown, and data is
limited (subset of measurable variables, often with noise). An
emerging field, `algebraic systems biology', offers algebraic
approaches to study problems systems biology. We present an
algebro-geometric method for ruling out models with limited
information and apply it to a biological system known to dysfunction
in many colorectal cancers. We are currently extending the framework
to include dynamics (i.e. time course data) using differential algebra
elimination and will present preliminary results.
Systems biology aims to understand the molecular interactions that
turn genes on/off, ultimately regulating cellular decisions. These
interactions may be described by a mathematical model that is a
polynomial dynamical system. Generally these interactions are unknown,
leading to multiple models; therefore it is desirable to compare
models with experimental data (e.g., steady-state concentrations of
proteins). Often model parameter values are unknown, and data is
limited (subset of measurable variables, often with noise). An
emerging field, `algebraic systems biology', offers algebraic
approaches to study problems systems biology. We present an
algebro-geometric method for ruling out models with limited
information and apply it to a biological system known to dysfunction
in many colorectal cancers. We are currently extending the framework
to include dynamics (i.e. time course data) using differential algebra
elimination and will present preliminary results.
Posted by: KCL
November 2015
Thu
26 Nov 2015
Sporadic and Exceptional
Yang-Hui He
(City)
Abstract:
We study the web of correspondences linking the exceptional Lie algebras E8,7,6 and the sporadic simple groups Monster, Baby and the largest Fischer group.
We will survey some old observations from the perspective of Moonshine and representation theory and present some new ones from that of congruence groups and enumerative geometry.
Based on joint work with John McKay.
We study the web of correspondences linking the exceptional Lie algebras E8,7,6 and the sporadic simple groups Monster, Baby and the largest Fischer group.
We will survey some old observations from the perspective of Moonshine and representation theory and present some new ones from that of congruence groups and enumerative geometry.
Based on joint work with John McKay.
Posted by: QMW
Wed
25 Nov 2015
Black hole microstates in AdS from gauge theory
📍 London
Francesco Benini
(Imperial College)
Abstract:
One of the great successes of string theory, as a theory of quantum gravity, is the explanation of the entropy of asymptotically-flat black holes. I will present, instead, a counting of the microstates of certain black holes in AdS4. The black holes have an holographic description as RG flows from a 3D CFT to superconformal quantum mechanics, and the counting of microstates proceeds via supersymmetric localization. Along the way, we will define and compute an index for topologically twisted theories, and propose an extremization principle to determine the superconformal R-symmetry in quantum mechanics.
One of the great successes of string theory, as a theory of quantum gravity, is the explanation of the entropy of asymptotically-flat black holes. I will present, instead, a counting of the microstates of certain black holes in AdS4. The black holes have an holographic description as RG flows from a 3D CFT to superconformal quantum mechanics, and the counting of microstates proceeds via supersymmetric localization. Along the way, we will define and compute an index for topologically twisted theories, and propose an extremization principle to determine the superconformal R-symmetry in quantum mechanics.
Posted by: KCL
Wed
25 Nov 2015
Solving the Scattering Equations
Peter Goddard
(IAS)
Abstract:
Describing work in collaboration with Louise Dolan, I will discuss the scattering equations, originally introduced in 1972 by Fairlie and Roberts searching for new dual models, rediscovered by Gross and Mende in 1988, discussing the high energy behaviour of string theory, and more recently shown by Cachazo, He and Yuan to provide a kinematic basis for describing remarkable formulae for tree amplitudes for massless particles in arbitrary space-time dimension (including scalars, gauge bosons and gravitons). We reformulate the scattering equations for N particles as a system of N -3 homogeneous polynomial equations in N - 2 complex variables, which are linear in each variable separately. The linearity of the equations enables their explicit solution in terms of the roots of a single-variable polynomial of degree (N-3)!, which can itself be explicitly constructed in terms of the Mandelstam variables formed from the momenta. The possible extension to one loop and the special case of four-dimensional space-time will also be briefly discussed.
Describing work in collaboration with Louise Dolan, I will discuss the scattering equations, originally introduced in 1972 by Fairlie and Roberts searching for new dual models, rediscovered by Gross and Mende in 1988, discussing the high energy behaviour of string theory, and more recently shown by Cachazo, He and Yuan to provide a kinematic basis for describing remarkable formulae for tree amplitudes for massless particles in arbitrary space-time dimension (including scalars, gauge bosons and gravitons). We reformulate the scattering equations for N particles as a system of N -3 homogeneous polynomial equations in N - 2 complex variables, which are linear in each variable separately. The linearity of the equations enables their explicit solution in terms of the roots of a single-variable polynomial of degree (N-3)!, which can itself be explicitly constructed in terms of the Mandelstam variables formed from the momenta. The possible extension to one loop and the special case of four-dimensional space-time will also be briefly discussed.
Posted by: IC
Tue
24 Nov 2015
Energy Gaps and Casimir Energies in Holographic CFTs
📍 London
Andrew Hickling
(Imperial College)
Abstract:
Two interesting properties of static curved space QFTs are Casimir Energies, and the Energy Gaps of fluctuations. We investigate what AdS/CFT has to say about these properties by examining holographic CFTs defined on curved but static spatially closed spacetimes. Being holographic, these CFTs have a dual gravitational description under Gauge/Gravity duality, and these properties of the CFT are reflected in the geometry of the dual bulk. We can turn this on its head and ask, what does the existence of the gravitational bulk dual imply about these properties of the CFTs? In this talk we will consider holographic CFTs where the dual vacuum state is described by pure Einstein gravity with negative cosmological constant. We will argue using the bulk geometry first, that if the CFT spacetime's spatial scalar curvature is positive there is a lower bound on the gap for scalar fluctuations, controlled by the minimum value of the boundary Ricci scalar. In fact, we will show that it is precisely the same bound as is satisfied by free scalar CFTs, suggesting that this bound might be something that applies more generally than just in a Holographic context. We will then show, in the case of 2+1 dimensional CFTs, that the Casimir energy is non-positive, and is in fact negative unless the CFT's scalar curvature is constant. In this case, there is no restriction on the boundary scalar curvature, and we can even allow singularities in the bulk, so long as they are 'good' singularities. If time permits, we will also describe some new results about the Hawking-Page transition in this context.
Two interesting properties of static curved space QFTs are Casimir Energies, and the Energy Gaps of fluctuations. We investigate what AdS/CFT has to say about these properties by examining holographic CFTs defined on curved but static spatially closed spacetimes. Being holographic, these CFTs have a dual gravitational description under Gauge/Gravity duality, and these properties of the CFT are reflected in the geometry of the dual bulk. We can turn this on its head and ask, what does the existence of the gravitational bulk dual imply about these properties of the CFTs? In this talk we will consider holographic CFTs where the dual vacuum state is described by pure Einstein gravity with negative cosmological constant. We will argue using the bulk geometry first, that if the CFT spacetime's spatial scalar curvature is positive there is a lower bound on the gap for scalar fluctuations, controlled by the minimum value of the boundary Ricci scalar. In fact, we will show that it is precisely the same bound as is satisfied by free scalar CFTs, suggesting that this bound might be something that applies more generally than just in a Holographic context. We will then show, in the case of 2+1 dimensional CFTs, that the Casimir energy is non-positive, and is in fact negative unless the CFT's scalar curvature is constant. In this case, there is no restriction on the boundary scalar curvature, and we can even allow singularities in the bulk, so long as they are 'good' singularities. If time permits, we will also describe some new results about the Hawking-Page transition in this context.
Posted by: KCL
Tue
24 Nov 2015
tba
Tom Leinster
(Edinburgh)
Thu
19 Nov 2015
5d theories on curved backgrounds, Yang-Mills deformations and instantons
Diego Rodriguez-Gomez
(Universidad de Oviedo)
Abstract:
5d theories can be at fixed points, in many cases exhibiting rather amusing properties. In this talk we will study several properties of these fixed point theories. In particular, we will describe how to put them supersymmetrically in curved spaces. As a consequence, we will discuss when a deformation to a Yang-Mills theory is possible. The latter typically exhibit a smaller global symmetry that that of the fixed point theory, which, from the YM point of view, appears as an enhanced symmetry. In this enhancement instantons play a pivotal role, and we will discuss several aspects of these.
5d theories can be at fixed points, in many cases exhibiting rather amusing properties. In this talk we will study several properties of these fixed point theories. In particular, we will describe how to put them supersymmetrically in curved spaces. As a consequence, we will discuss when a deformation to a Yang-Mills theory is possible. The latter typically exhibit a smaller global symmetry that that of the fixed point theory, which, from the YM point of view, appears as an enhanced symmetry. In this enhancement instantons play a pivotal role, and we will discuss several aspects of these.
Posted by: QMW
Wed
18 Nov 2015
The Cluster Bootstrap for Scattering Amplitudes
📍 London
James Drummond
(Southampton)
Wed
18 Nov 2015
Polygon Seminar: An introduction to the Hilbert series as operator counting
Diego Rodriguez-Gomez
(University of Oviedo)
Abstract:
Counting operators in supersymmetric field theories is very interesting, as the corresponding generating functions encode properties of the field theory. In this lecture we will mostly concentrate on 4d SUSY field theories.
After reviewing some basic notions about SUSY field theories leading to the notion of chiral ring, we will introduce a generating function enumerating operators in the ring. This function is the so-called Hilbert series. In the case of SCFTs with a gravity dual, we will show how this function recovers geometric properties of the dual gravity background.
The uses of the Hilbert series go beyond this, since, as we will see, being a counting of operators, it is of relevance in the computation of instanton partition functions for pure gauge theories. In the second part of the lecture
we will briefly touch upon these issues.
Counting operators in supersymmetric field theories is very interesting, as the corresponding generating functions encode properties of the field theory. In this lecture we will mostly concentrate on 4d SUSY field theories.
After reviewing some basic notions about SUSY field theories leading to the notion of chiral ring, we will introduce a generating function enumerating operators in the ring. This function is the so-called Hilbert series. In the case of SCFTs with a gravity dual, we will show how this function recovers geometric properties of the dual gravity background.
The uses of the Hilbert series go beyond this, since, as we will see, being a counting of operators, it is of relevance in the computation of instanton partition functions for pure gauge theories. In the second part of the lecture
we will briefly touch upon these issues.
Posted by: QMW
Tue
17 Nov 2015
On the origins of the viscous instability mechanism
Jonathan Healey
(Keele)
Thu
12 Nov 2015
Supersymmetric Defects in 3d-3d Correspondence
📍 London
Masahito Yamazaki
(IPMU)
Abstract:
In this talk I will describe co-dimension 2 and 4 defects in 6d (2,0) theories in several points of view:
3d SL(N,C) Chern-Simons theory (state-integral model, cluster algebra), 3d N=2 field theory, 5d N=2 super Yang-Mills,
and AdS4 holographic dual. This leads to quantitative consistency checks of different approaches, as well as new
predictions for a variety of partition functions.
In this talk I will describe co-dimension 2 and 4 defects in 6d (2,0) theories in several points of view:
3d SL(N,C) Chern-Simons theory (state-integral model, cluster algebra), 3d N=2 field theory, 5d N=2 super Yang-Mills,
and AdS4 holographic dual. This leads to quantitative consistency checks of different approaches, as well as new
predictions for a variety of partition functions.
Posted by: KCL
Thu
12 Nov 2015
Exact Results for Entanglement and Renyi Entropies, and their Gravity Duals
Julian Sonner
(University of Geneva)
Abstract:
The recent focus on entanglement entropy in holography has many motivations, ranging from the applied (e.g. AdS/CMT) to the foundational (emergence of gravity). For all of these programs It is important to find examples, where the quantities of interest can be directly calculated in strongly-coupled field theories and, moreover, the dual geometry constructed at strong coupling.
In this talk I will describe joint work with Crossley and Dyer on using localization methods to obtain entanglement and (super-) Renyi entropies of the N=4 SYM theory with gauge group SU(N) in 4D at all values of the ’t Hooft coupling \lambda and number of colors N.
Since obtaining quantities like entanglement and Renyi entropies involves working on singular spaces, which typically break the supersymmetry, we focus on a supersymmetric generalization, the so-called super-Renyi entropy where the supersymmetry breaking effects of the singularities are suitably compensated. I will also discuss dual gravity solutions as five-dimensional BPS black holes with hyperbolic horizon. I will conclude with a description of Wilson loops, that is the contribution to the entanglement and Renyi entropies due to adding fundamental matter to the theory.
The recent focus on entanglement entropy in holography has many motivations, ranging from the applied (e.g. AdS/CMT) to the foundational (emergence of gravity). For all of these programs It is important to find examples, where the quantities of interest can be directly calculated in strongly-coupled field theories and, moreover, the dual geometry constructed at strong coupling.
In this talk I will describe joint work with Crossley and Dyer on using localization methods to obtain entanglement and (super-) Renyi entropies of the N=4 SYM theory with gauge group SU(N) in 4D at all values of the ’t Hooft coupling \lambda and number of colors N.
Since obtaining quantities like entanglement and Renyi entropies involves working on singular spaces, which typically break the supersymmetry, we focus on a supersymmetric generalization, the so-called super-Renyi entropy where the supersymmetry breaking effects of the singularities are suitably compensated. I will also discuss dual gravity solutions as five-dimensional BPS black holes with hyperbolic horizon. I will conclude with a description of Wilson loops, that is the contribution to the entanglement and Renyi entropies due to adding fundamental matter to the theory.
Posted by: QMW
Wed
11 Nov 2015
Graduate Lectures: A first introduction to string amplitudes III
Rodolfo Russo
(Queen Mary)
Abstract:
Lecture 3: An example of mixed open/closed amplitudes
Lecture 3: An example of mixed open/closed amplitudes
Posted by: QMW
Wed
11 Nov 2015
Black holes with a single Killing vector field: black resonators
📍 London
Jorge Santos
(DAMTP, Cambridge)
Abstract:
We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
Posted by: KCL
Wed
11 Nov 2015
Exact Results for Entanglement and Renyi Entropies, and their Gravity Duals
Julian Sonner
(University of Geneva)
Abstract:
The recent focus on entanglement entropy in holography has many motivations, ranging from the applied (e.g. AdS/CMT) to the foundational (emergence of gravity). For all of these programs It is important to find examples, where the quantities of interest can be directly calculated in strongly-coupled field theories and, moreover, the dual geometry constructed at strong coupling.
In this talk I will describe joint work with Crossley and Dyer on using localization methods to obtain entanglement and (super-) Renyi entropies of the N=4 SYM theory with gauge group SU(N) in 4D at all values of the ’t Hooft coupling \lambda and number of colors N.
Since obtaining quantities like entanglement and Renyi entropies involves working on singular spaces, which typically break the supersymmetry, we focus on a supersymmetric generalization, the so-called super-Renyi entropy where the supersymmetry breaking effects of the singularities are suitably compensated. I will also discuss dual gravity solutions as five-dimensional BPS black holes with hyperbolic horizon. I will conclude with a description of Wilson loops, that is the contribution to the entanglement and Renyi entropies due to adding fundamental matter to the theory.
The recent focus on entanglement entropy in holography has many motivations, ranging from the applied (e.g. AdS/CMT) to the foundational (emergence of gravity). For all of these programs It is important to find examples, where the quantities of interest can be directly calculated in strongly-coupled field theories and, moreover, the dual geometry constructed at strong coupling.
In this talk I will describe joint work with Crossley and Dyer on using localization methods to obtain entanglement and (super-) Renyi entropies of the N=4 SYM theory with gauge group SU(N) in 4D at all values of the ’t Hooft coupling \lambda and number of colors N.
Since obtaining quantities like entanglement and Renyi entropies involves working on singular spaces, which typically break the supersymmetry, we focus on a supersymmetric generalization, the so-called super-Renyi entropy where the supersymmetry breaking effects of the singularities are suitably compensated. I will also discuss dual gravity solutions as five-dimensional BPS black holes with hyperbolic horizon. I will conclude with a description of Wilson loops, that is the contribution to the entanglement and Renyi entropies due to adding fundamental matter to the theory.
Posted by: IC
Tue
10 Nov 2015
Graduate Lectures: A first introduction to string amplitudes II
Rodolfo Russo
(Queen Mary)
Abstract:
Lecture 2: Derivation of the Virasoro-Shapiro amplitude; 4 graviton amplitude in the superstring (no derivation, but discussion of the low and high energy limits)
Lecture 2: Derivation of the Virasoro-Shapiro amplitude; 4 graviton amplitude in the superstring (no derivation, but discussion of the low and high energy limits)
Posted by: QMW
Tue
10 Nov 2015
tba
Lucas Lacasa
(QMUL)
Wed
4 Nov 2015
Thermalization in 2d CFTs revisited
Jan de Boer
(Amsterdam U.)
Abstract:
While a lot of work has been done on understanding thermalization in 2d CFTs, several confusing
aspects remain, in particular regarding integrable aspects of 2d CFTs. In this talk I will try to summarize
some of these confusions and how these connect to AdS/CFT and black hole formation. There appears
to be a significant difference between thermalization in low c CFTs versus thermalization in large c CFTs with
gravitational duals.
While a lot of work has been done on understanding thermalization in 2d CFTs, several confusing
aspects remain, in particular regarding integrable aspects of 2d CFTs. In this talk I will try to summarize
some of these confusions and how these connect to AdS/CFT and black hole formation. There appears
to be a significant difference between thermalization in low c CFTs versus thermalization in large c CFTs with
gravitational duals.
Posted by: IC
Wed
4 Nov 2015
Black holes, Stokes flows and DC transport at strong coupling
Aristomenis Donos
(Durham U.)
Abstract:
Certain materials, such as the cuprate superconductors and heavy fermion materials exhibit fascinating, yet hard to explain transport properties. Holography provides a consistent framework to examine linear response and in particular transport of strongly coupled matter. I will discuss momentum dissipation in holography and show that DC transport is fixed via a Stokes flow of an "auxiliary fluid" residing on the horizon of black holes.
Certain materials, such as the cuprate superconductors and heavy fermion materials exhibit fascinating, yet hard to explain transport properties. Holography provides a consistent framework to examine linear response and in particular transport of strongly coupled matter. I will discuss momentum dissipation in holography and show that DC transport is fixed via a Stokes flow of an "auxiliary fluid" residing on the horizon of black holes.
Posted by: IC
Mon
2 Nov 2015
Graduate Lectures: A first introduction to string amplitudes I
Rodolfo Russo
(Queen Mary)
Abstract:
Lecture 1: Veneziano amplitude: derivation, low and high energy limits
Lecture 1: Veneziano amplitude: derivation, low and high energy limits
Posted by: QMW
October 2015
Thu
29 Oct 2015
The (2,0) superconformal bootstrap
Balt van Rees
(Durham)
Abstract:
In recent years we have witnessed a revival of the conformal bootstrap approach to CFTs. I will discuss the application of these ideas to six-dimensional conformal field theories with (2,0) supersymmetry, focusing on the universal four-point function of stress tensor multiplets. For these theories the program splits into an analytic and a numerical component. The analytic component yields exact results but in a protected subsector. The numerical component can be used to derive bounds on OPE coefficients and scaling dimensions from the constraints of crossing symmetry and unitarity. The principal numerical result is strong evidence that the A1 theory realizes the minimal allowed central charge (c=25) for any interacting (2,0) theory. This implies that the full stress tensor four-point function of the A1 theory is the unique unitary solution to the crossing symmetry equation at c=25. For this theory, we can estimate the scaling dimensions of the lightest unprotected operators appearing in the stress tensor operator product expansion. We also find rigorous upper bounds for dimensions and OPE coefficients for a general interacting (2,0) theory of central charge c. For large c, our bounds appear to be saturated by the holographic predictions obtained from eleven-dimensional supergravity.
In recent years we have witnessed a revival of the conformal bootstrap approach to CFTs. I will discuss the application of these ideas to six-dimensional conformal field theories with (2,0) supersymmetry, focusing on the universal four-point function of stress tensor multiplets. For these theories the program splits into an analytic and a numerical component. The analytic component yields exact results but in a protected subsector. The numerical component can be used to derive bounds on OPE coefficients and scaling dimensions from the constraints of crossing symmetry and unitarity. The principal numerical result is strong evidence that the A1 theory realizes the minimal allowed central charge (c=25) for any interacting (2,0) theory. This implies that the full stress tensor four-point function of the A1 theory is the unique unitary solution to the crossing symmetry equation at c=25. For this theory, we can estimate the scaling dimensions of the lightest unprotected operators appearing in the stress tensor operator product expansion. We also find rigorous upper bounds for dimensions and OPE coefficients for a general interacting (2,0) theory of central charge c. For large c, our bounds appear to be saturated by the holographic predictions obtained from eleven-dimensional supergravity.
Posted by: QMW
Wed
28 Oct 2015
Ambitwistor strings and the scattering equations at one loop
📍 London
Lionel Mason
(Oxford University)
Abstract:
Ambitwistor strings are holomorphic string theories whose target space is the space of complex null geoedesics in complexified space-times. I will explain how these theories explain the origin of the scattering equations in twistor strings and the CHY formulae in arbitrary dimensions and provide a reformulation of standard gauge, gravity and other theories in a holomorphic infinite tension analogue of conventional string theories. I will show how these results extend to 1-loop both on a torus and on a nodal Riemann sphere, and perhaps to higher loops.
Ambitwistor strings are holomorphic string theories whose target space is the space of complex null geoedesics in complexified space-times. I will explain how these theories explain the origin of the scattering equations in twistor strings and the CHY formulae in arbitrary dimensions and provide a reformulation of standard gauge, gravity and other theories in a holomorphic infinite tension analogue of conventional string theories. I will show how these results extend to 1-loop both on a torus and on a nodal Riemann sphere, and perhaps to higher loops.
Posted by: KCL
Wed
28 Oct 2015
Knots in 3d-3d Correspondence
Masahito Yamazaki
(Kavli IPMU)
Abstract:
I will discuss knot-like defects in CS theory with complex
gauge group SL(N), in the context of its connection with 3d N=2 theory (the so-called 3d-3d correspondence). I am hoping to discuss this problem from a number of different
perspectives, including cluster algebras, state-integral models, 3d N=2 non-Abelian gauge theories, 5d N=2 SYM,
and holographic dual, and discuss the consistency checks as well as new predictions/implications. This talk is mostly based on my recent papers with D. Gang, N. Kim and M. Romo.
I will discuss knot-like defects in CS theory with complex
gauge group SL(N), in the context of its connection with 3d N=2 theory (the so-called 3d-3d correspondence). I am hoping to discuss this problem from a number of different
perspectives, including cluster algebras, state-integral models, 3d N=2 non-Abelian gauge theories, 5d N=2 SYM,
and holographic dual, and discuss the consistency checks as well as new predictions/implications. This talk is mostly based on my recent papers with D. Gang, N. Kim and M. Romo.
Posted by: IC
Tue
27 Oct 2015
tba
Tobias Galla
(Manchester)
Fri
23 Oct 2015
Network Geometry
Ginestra Bianconi
(Queen Mary)
Abstract:
Networks are mathematical structures that are universally used to describe a large variety of complex systems such as the brain or the Internet. Characterizing the geometrical properties of these networks has become increasingly relevant for routing problems, inference and data mining. In real growing networks, topological, structural and geometrical properties emerge spontaneously from their dynamical rules. Here we show that a single two parameter model of emergent network geometry, constructed by gluing triangles, can generate complex network geometries with non-trivial distribution of curvatures, combining exponential growth and small-world properties with finite spectral dimensionality. In one limit, the non-equilibrium dynamical rules of these networks can generate scale-free networks with clustering and communities, in another limit 2 dimensional manifolds with non-trivial modularity. When manifolds of arbitrary dimension are constructed, and energies are assigned to their nodes these networks can be mapped to quantum network states and they follows quantum statistics despite they do not obey equilibrium statistical mechanics.
Networks are mathematical structures that are universally used to describe a large variety of complex systems such as the brain or the Internet. Characterizing the geometrical properties of these networks has become increasingly relevant for routing problems, inference and data mining. In real growing networks, topological, structural and geometrical properties emerge spontaneously from their dynamical rules. Here we show that a single two parameter model of emergent network geometry, constructed by gluing triangles, can generate complex network geometries with non-trivial distribution of curvatures, combining exponential growth and small-world properties with finite spectral dimensionality. In one limit, the non-equilibrium dynamical rules of these networks can generate scale-free networks with clustering and communities, in another limit 2 dimensional manifolds with non-trivial modularity. When manifolds of arbitrary dimension are constructed, and energies are assigned to their nodes these networks can be mapped to quantum network states and they follows quantum statistics despite they do not obey equilibrium statistical mechanics.
Posted by: QMW
Thu
22 Oct 2015
T-Self Duality of AdS(d) x S(d) x S(d) Superstrings
Antonio Pittelli
(Surrey University)
Abstract:
Dual superconformal symmetry is a remarkable, hidden feature of N=4 SYM in 4 dimensions. Via AdS/CFT, such a symmetry corresponds to the invariance of the AdS(5) x S(5) superstring under specific combinations of bosonic and fermionic T-dualities.
We show that AdS(d) x S(d) x S(d) superstrings with D(2,1;\alpha) isometry supergroup are T-self-dual if additional T-dualities along complexified S(d) directions are performed. This implies that CFTs dual to AdS(d) x S(d) x S(d) x T(10-3d) superstrings enjoy a new type of dual superconformal symmetry.
Dual superconformal symmetry is a remarkable, hidden feature of N=4 SYM in 4 dimensions. Via AdS/CFT, such a symmetry corresponds to the invariance of the AdS(5) x S(5) superstring under specific combinations of bosonic and fermionic T-dualities.
We show that AdS(d) x S(d) x S(d) superstrings with D(2,1;\alpha) isometry supergroup are T-self-dual if additional T-dualities along complexified S(d) directions are performed. This implies that CFTs dual to AdS(d) x S(d) x S(d) x T(10-3d) superstrings enjoy a new type of dual superconformal symmetry.
Posted by: IC
Thu
22 Oct 2015
String theory effective actions and universality of alpha' corrections to BPS,non-BPS systems
Ehsan Hatefi
(Queen Mary)
Abstract:
We start by providing complete insights about the standard ways of finding couplings in effective field theory , and present most of the supersymmetric and non-supersymmetric scattering amplitudes of both type IIA,IIB superstring theory as well as their corrections.
We would also like to address the way of obtaining a universal conjecture for DBI, Chern-Simons and new Wess Zumino actions with their corrections. We then move on to provide a comprehensive explanation even for D- brane-anti D-brane systems, where various new techniques will be also illustrated.
If time allows , we then mention several issues related to those effective actions and eventually highlight some open problems.
We start by providing complete insights about the standard ways of finding couplings in effective field theory , and present most of the supersymmetric and non-supersymmetric scattering amplitudes of both type IIA,IIB superstring theory as well as their corrections.
We would also like to address the way of obtaining a universal conjecture for DBI, Chern-Simons and new Wess Zumino actions with their corrections. We then move on to provide a comprehensive explanation even for D- brane-anti D-brane systems, where various new techniques will be also illustrated.
If time allows , we then mention several issues related to those effective actions and eventually highlight some open problems.
Posted by: QMW
Wed
21 Oct 2015
Seiberg Dualities from Non-Supersymmetric Brane Configurations
📍 London
Adi Armoni
(Swansea University)
Abstract:
In this talk I will consider brane configurations that include NS5 branes, orientifold planes and anti-branes. I will argue that the class of field theories that live on such brane configurations admit Seiberg duality. Interactions between branes and orientifold planes will be given a field theory interpretation. In particular a certain repulsive interaction will lead to a non-trivial Coleman-Weinberg potential and dynamical symmetry breaking.
I will also discuss the case of type 0' strings and chiral symmetry breaking of the form SU(Nf)xSU(Nf)–>SU(Nf) in a QCD-like theory.
In this talk I will consider brane configurations that include NS5 branes, orientifold planes and anti-branes. I will argue that the class of field theories that live on such brane configurations admit Seiberg duality. Interactions between branes and orientifold planes will be given a field theory interpretation. In particular a certain repulsive interaction will lead to a non-trivial Coleman-Weinberg potential and dynamical symmetry breaking.
I will also discuss the case of type 0' strings and chiral symmetry breaking of the form SU(Nf)xSU(Nf)–>SU(Nf) in a QCD-like theory.
Posted by: KCL
Wed
21 Oct 2015
Algebras and Correlators
Sanjaye Ramgoolam
(QMUL)
Abstract:
**** POLYGON SEMINAR****
Permutation groups and related algebras have proved to be powerful tools for understanding the counting and correlators of gauge invariant operators in 1-Matrix and multi-matrix models. Mathematical structures such as Belyi maps underlying the mixing of trace structures have been uncovered and finite N effects have been encoded using Young diagram data. These results have found applications in studies of BPS, near-BPS and non-BPS operators in N=4 SYM and quiver gauge theories. I will review some of this work and describe some open problems.
**** POLYGON SEMINAR****
Permutation groups and related algebras have proved to be powerful tools for understanding the counting and correlators of gauge invariant operators in 1-Matrix and multi-matrix models. Mathematical structures such as Belyi maps underlying the mixing of trace structures have been uncovered and finite N effects have been encoded using Young diagram data. These results have found applications in studies of BPS, near-BPS and non-BPS operators in N=4 SYM and quiver gauge theories. I will review some of this work and describe some open problems.
Posted by: KCL
Tue
20 Oct 2015
tba
Steve Baigent
(UCL)
Thu
15 Oct 2015
Interactions in Vasiliev's Theory, Holography and Locality
Massimo Taronna
(AEI)
Abstract:
The aim of this talk is to extract the quadratic corrections to Fronsdal equations from Vasiliev's equations, and discuss their structure. The issue of locality in higher-spin theories will be addressed. Implications of this analysis in relation to Giombi-Yin checks of higher-spin/vector model duality will be discussed. Some of the previous puzzles will be resolved, while others will be elucidated.
The aim of this talk is to extract the quadratic corrections to Fronsdal equations from Vasiliev's equations, and discuss their structure. The issue of locality in higher-spin theories will be addressed. Implications of this analysis in relation to Giombi-Yin checks of higher-spin/vector model duality will be discussed. Some of the previous puzzles will be resolved, while others will be elucidated.
Posted by: IC
Thu
15 Oct 2015
Loop integrands from the Riemann sphere
Piotr Tourkine
(Cambridge)
Abstract:
Remarkable formulae for the tree-level S-matrix of gauge and gravity
theories were recently discovered by Cachazo-He-Yuan, based on a
localisation procedure in the moduli space of Riemann surfaces.
These formulae are now known to arise from new string-like chiral
models. These naturally produces loop-level amplitudes, also localised
in the moduli space of higher genus curves.
However, the resolution of the localisation equations is immensely
more difficult than at tree-level, and it remained as an open question
as to what these formulae computed, and more generally if these string
models made sense at the quantum level.
In this talk I'll describe a resolution of the localisation equations
at one-loop in a particular kinematical regime, and show agreement
with known amplitudes.
Then I'll describe a much more powerful method, based on an
integration by parts which degenerates the torus down to a sphere
(plus two new points). The model is then solved like at
tree-level. I'll briefly discuss extension to higher loops in conclusion.
Remarkable formulae for the tree-level S-matrix of gauge and gravity
theories were recently discovered by Cachazo-He-Yuan, based on a
localisation procedure in the moduli space of Riemann surfaces.
These formulae are now known to arise from new string-like chiral
models. These naturally produces loop-level amplitudes, also localised
in the moduli space of higher genus curves.
However, the resolution of the localisation equations is immensely
more difficult than at tree-level, and it remained as an open question
as to what these formulae computed, and more generally if these string
models made sense at the quantum level.
In this talk I'll describe a resolution of the localisation equations
at one-loop in a particular kinematical regime, and show agreement
with known amplitudes.
Then I'll describe a much more powerful method, based on an
integration by parts which degenerates the torus down to a sphere
(plus two new points). The model is then solved like at
tree-level. I'll briefly discuss extension to higher loops in conclusion.
Posted by: QMW
Wed
14 Oct 2015
The Supersymmetric Quantum Hall Effect
📍 London
David Tong
(DAMTP, Cambridge)
Abstract:
There exist, in d=2+1 dimensions, field theories that are supersymmetric but non-relativistic. I will show that the low-energy physics of these theories is that of the fractional quantum Hall effect. Supersymmetry provides enough analytic control to explicitly derive the ground state wavefunctions and their excitations.
There exist, in d=2+1 dimensions, field theories that are supersymmetric but non-relativistic. I will show that the low-energy physics of these theories is that of the fractional quantum Hall effect. Supersymmetry provides enough analytic control to explicitly derive the ground state wavefunctions and their excitations.
Posted by: KCL
Wed
14 Oct 2015
All order alpha' corrections to BPS,non-BPS and brane anti-brane effective actions of type IIA,IIB superstring theory
Ehsan Hatefi
(Queen Mary)
Abstract:
We would like to talk about all kinds of supersymmetric and non-supersymmetric scattering amplitudes of type IIA,IIB superstring theory as well as their corrections.
In fact we want to address how to get to a universal conjecture for DBI, Chern-Simons and more importantly new Wess Zumino actions with their all order \(\alpha'\) corrections. Indeed we try to provide a comprehensive explanation even for D- brane-anti D-brane systems, where various new techniques will be also introduced. If time allows , we then mention several issues related to those effective actions and eventually highlight some comments about higher point functions of the Mixed closed string RR , scalar fields in different pictures of the string theory amplitude.
We would like to talk about all kinds of supersymmetric and non-supersymmetric scattering amplitudes of type IIA,IIB superstring theory as well as their corrections.
In fact we want to address how to get to a universal conjecture for DBI, Chern-Simons and more importantly new Wess Zumino actions with their all order \(\alpha'\) corrections. Indeed we try to provide a comprehensive explanation even for D- brane-anti D-brane systems, where various new techniques will be also introduced. If time allows , we then mention several issues related to those effective actions and eventually highlight some comments about higher point functions of the Mixed closed string RR , scalar fields in different pictures of the string theory amplitude.
Posted by: IC
Wed
14 Oct 2015
Simplifying amplitudes in N=2 Yang-Mills-Einstein supergravities
Marco Chiodaroli
(MPI)
Abstract:
The talk reports on recent progress in amplitude computations
for broad classes of N=2 Maxwell-Einstein and Yang-Mills-Einstein
supergravities, using the framework provided by color/kinematics duality
and the double-copy construction.
After a review of the main theoretical tools employed in the
computations, we discuss the extension of the double-copy construction
to a particular infinite family of N=2 Maxwell-Einstein supergravities
in four and five dimensions and show that the global symmetries of these
theories can easily be gauged, giving the amplitudes of the
corresponding Yang-Mills-Einstein supergravities. Finally, we discuss
how the construction can be modified to describe spontaneous symmetry
breaking and present examples at one loop.
The talk reports on recent progress in amplitude computations
for broad classes of N=2 Maxwell-Einstein and Yang-Mills-Einstein
supergravities, using the framework provided by color/kinematics duality
and the double-copy construction.
After a review of the main theoretical tools employed in the
computations, we discuss the extension of the double-copy construction
to a particular infinite family of N=2 Maxwell-Einstein supergravities
in four and five dimensions and show that the global symmetries of these
theories can easily be gauged, giving the amplitudes of the
corresponding Yang-Mills-Einstein supergravities. Finally, we discuss
how the construction can be modified to describe spontaneous symmetry
breaking and present examples at one loop.
Posted by: QMW
Tue
13 Oct 2015
tba
Nick Halmagyi
(Jussieu)
Thu
8 Oct 2015
All gaugings and stable de Sitter in D=7 half-maximal supergravity
Jose Fernandez-Melgarejo
(Harvard)
Abstract:
We study the general formulation of gauged supergravity in
seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry.
We study the general formulation of gauged supergravity in
seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry.
Posted by: IC
Thu
8 Oct 2015
Higher charge half-BPS four-point correlation functions in planar N=4 SYM
Paul Heslop
(Durham)
Abstract:
We will show how to obtain half-BPS four-point correlation
functions in N=4 SYM at up to 3 loops using symmetries, analytic
properties the Wilson loop/correlator duality, planarity and some
minimal knowledge of the OPE structure relating four-point correlators
of different charges. These can be used to verify recent predictions
for OPE coefficients arising from integrability.
We will show how to obtain half-BPS four-point correlation
functions in N=4 SYM at up to 3 loops using symmetries, analytic
properties the Wilson loop/correlator duality, planarity and some
minimal knowledge of the OPE structure relating four-point correlators
of different charges. These can be used to verify recent predictions
for OPE coefficients arising from integrability.
Posted by: QMW
Wed
7 Oct 2015
Geometric free energy of toric AdS4/CFT3 models
📍 London
Daisuke Yokoyama
(King's College London)
Abstract:
We study the free energy of the three dimensional N=2 supersymmetric Chern-Simons-Matter theory dual to AdS4 times toric seven dimensional Sasaki-Einstein manifold. Although it is not known in general how to construct the CSM theory from the geometric data of the 7d SE manifold (which is called toric diagram), the free energy in the large N limit may be derived.
We present the free energy as a quartic polynomial of trial R-charges for generic toric diagram with up to 6 vertices, and some particular diagrams with 8 vertices. The free energy reproduces the Martelli-Sparks-Yau volume function.
We study the free energy of the three dimensional N=2 supersymmetric Chern-Simons-Matter theory dual to AdS4 times toric seven dimensional Sasaki-Einstein manifold. Although it is not known in general how to construct the CSM theory from the geometric data of the 7d SE manifold (which is called toric diagram), the free energy in the large N limit may be derived.
We present the free energy as a quartic polynomial of trial R-charges for generic toric diagram with up to 6 vertices, and some particular diagrams with 8 vertices. The free energy reproduces the Martelli-Sparks-Yau volume function.
Posted by: KCL
September 2015
Wed
23 Sep 2015
Supersymmetric Localization for BPS Black Hole Entropy: 1-loop Partition Function from Vector Multiplets
📍 London
Imtak Jeon
(KIAS)
Abstract:
We use the techniques of supersymmetric localization to compute the BPS black hole entropy in N=2 supergravity. We focus on the n_v+1 vector multiplets on the black hole near horizon background which is AdS_2 x S^2 space. We find the localizing saddle point of the vector multiplets by solving the localization equations, and compute the exact one loop
partition function on the saddle point. Furthermore, we propose the appropriate functional integration measure. Through this measure, the one loop determinant is written in terms of the radius of the physical metric, which depends on the localizing saddle point value of the vector multiplets. The result for the one loop determinant is consistent with the logarithmic corrections to the BPS black hole entropy from vector multiplets.
We use the techniques of supersymmetric localization to compute the BPS black hole entropy in N=2 supergravity. We focus on the n_v+1 vector multiplets on the black hole near horizon background which is AdS_2 x S^2 space. We find the localizing saddle point of the vector multiplets by solving the localization equations, and compute the exact one loop
partition function on the saddle point. Furthermore, we propose the appropriate functional integration measure. Through this measure, the one loop determinant is written in terms of the radius of the physical metric, which depends on the localizing saddle point value of the vector multiplets. The result for the one loop determinant is consistent with the logarithmic corrections to the BPS black hole entropy from vector multiplets.
Posted by: KCL