Triangle Seminars
December 2014
Wed
17 Dec 2014
Local Poisson brackets in classical field theory
Ezra Getzler
(Northwestern)
Tue
16 Dec 2014
Gravity as gauge theory squared: from amplitudes to black holes
Ricardo Monteiro
(Oxford U., Inst. Math.)
Abstract:
We will discuss the relation between perturbative gauge theory and perturbative gravity, and look at how this relation extends to some exact classical
solutions. First, we will review the double copy prescription that takes gauge theory amplitudes into gravity amplitudes, which has been crucial to progress in perturbative studies of supergravity. Then, we will see that the self-dual sectors provide an important
insight into the relation between the theories. A key role is played by a kinematic algebraic structure mirroring the colour structure. Finally, we will see how these ideas extend to some exact classical solutions, namely black holes and plane waves. This
leads to a relation of the type Schwarzschild as Coulomb charge squared.
We will discuss the relation between perturbative gauge theory and perturbative gravity, and look at how this relation extends to some exact classical
solutions. First, we will review the double copy prescription that takes gauge theory amplitudes into gravity amplitudes, which has been crucial to progress in perturbative studies of supergravity. Then, we will see that the self-dual sectors provide an important
insight into the relation between the theories. A key role is played by a kinematic algebraic structure mirroring the colour structure. Finally, we will see how these ideas extend to some exact classical solutions, namely black holes and plane waves. This
leads to a relation of the type Schwarzschild as Coulomb charge squared.
Posted by: IC
Fri
12 Dec 2014
What is the equation of state for the early Universe?
Samir Mathur
(Ohio State)
Abstract:
The Bekenstein-Hawking formula for the entropy of a black hole suggests that entropy in strong gravity situations should be proportional to bounding area rather than enclosed volume. But we argue that the S and T dualities of string theory suggest an entropy formula that is extensive in the volume, with the area formula appearing as a special case. In particular we find a set of states in string theory that violate the covariant entropy bound, which seeks to extend the area entropy formula to situations like the early Universe.
The Bekenstein-Hawking formula for the entropy of a black hole suggests that entropy in strong gravity situations should be proportional to bounding area rather than enclosed volume. But we argue that the S and T dualities of string theory suggest an entropy formula that is extensive in the volume, with the area formula appearing as a special case. In particular we find a set of states in string theory that violate the covariant entropy bound, which seeks to extend the area entropy formula to situations like the early Universe.
Posted by: QMW
Thu
11 Dec 2014
Generic Predictions of String/M theory solutions with Low Energy Supersymmetry breaking
Bobby Acharya
(King's)
Abstract:
By studying the cosmological dynamics of the moduli and axion fields we develop a set of "generic predictions" of solutions to string/M theory which have low energy supersymmetry breaking and grand unification. The nature of dark matter plays an important role in much of the discussion.
By studying the cosmological dynamics of the moduli and axion fields we develop a set of "generic predictions" of solutions to string/M theory which have low energy supersymmetry breaking and grand unification. The nature of dark matter plays an important role in much of the discussion.
Posted by: QMW
Wed
10 Dec 2014
Eta Products, BPS States and K3 Surfaces
📍 London
Yang-Hui He
(City University)
Abstract:
Inspired by the multiplicative nature of the Ramanujan modular discriminant, Delta, we consider physical realizations of certain multiplicative products over the Dedekind eta-function in two parallel directions: the generating function of BPS states in certain heterotic orbifolds and elliptic K3 surfaces associated to congruence subgroups of the modular group. We show that they are, after string duality to type II, the same K3 surfaces admitting Nikulin automorphisms. In due course, we will present some identities arising from q-expansions as well as relations to the sporadic Mathieu group M24.
Inspired by the multiplicative nature of the Ramanujan modular discriminant, Delta, we consider physical realizations of certain multiplicative products over the Dedekind eta-function in two parallel directions: the generating function of BPS states in certain heterotic orbifolds and elliptic K3 surfaces associated to congruence subgroups of the modular group. We show that they are, after string duality to type II, the same K3 surfaces admitting Nikulin automorphisms. In due course, we will present some identities arising from q-expansions as well as relations to the sporadic Mathieu group M24.
Posted by: KCL
Wed
10 Dec 2014
Localization and quantum AdS_4/CFT_3 holography
Nadav Drukker
(King's College)
Abstract:
I will review the calculation of the partition function of 3d supersymmetric field theories on S^3 using the fermi-gas approach to solve the matrix integral. The resulting expression is an Airy function and is valid perturbatively to all orders in 1/N for a wide class of theories (including ABJM). This suggests that a similar formula can be derived by studying quantum gravity on AdS_4. I will explain several of the steps needed to implement this idea and some intriguing results.
I will review the calculation of the partition function of 3d supersymmetric field theories on S^3 using the fermi-gas approach to solve the matrix integral. The resulting expression is an Airy function and is valid perturbatively to all orders in 1/N for a wide class of theories (including ABJM). This suggests that a similar formula can be derived by studying quantum gravity on AdS_4. I will explain several of the steps needed to implement this idea and some intriguing results.
Posted by: IC
Tue
9 Dec 2014
TBA
James Lidsey
(Queen Mary University of London)
Abstract:
TBA
TBA
Posted by: IC
Wed
3 Dec 2014
Quantum entanglement of localized excited states at finite temperature
📍 London
Joan Simon
(University of Edinburgh)
Abstract:
Motivated by either condensed matter or quantum gravity holographic considerations, I will discuss some preliminary work on how to compute the time evolution in Renyi entropies in 2d CFTs in the large c limit for thermal states perturbed by localized primary operators. Time permitting, I will comment on the potential relation between this work and previous holographic calculations in the context of the EPR=ER conjecture.
Motivated by either condensed matter or quantum gravity holographic considerations, I will discuss some preliminary work on how to compute the time evolution in Renyi entropies in 2d CFTs in the large c limit for thermal states perturbed by localized primary operators. Time permitting, I will comment on the potential relation between this work and previous holographic calculations in the context of the EPR=ER conjecture.
Posted by: KCL
Wed
3 Dec 2014
Entanglement entropy: some recent developments
Solodukhin Sergey
(Tours)
Abstract:
In my talk I will give a brief review on entanglement entropy and discuss some recent developments which include relations to the geometric Willmore conjecture and the role of total derivatives in the trace anomaly.
In my talk I will give a brief review on entanglement entropy and discuss some recent developments which include relations to the geometric Willmore conjecture and the role of total derivatives in the trace anomaly.
Posted by: IC
Wed
3 Dec 2014
Polygon Seminar: Gauge Theories and Calabi-Yau Manifolds
Yang-Hui He
(City University)
Tue
2 Dec 2014
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 2014
Thu
27 Nov 2014
Interacting UV fixed points - from 4D quantum gauge theories to 4D quantum gravity
Daniel Litim
(Sussex U.)
Abstract:
It is commonly believed that for a quantum field theory to be fundamental,
its high-energy behaviour must be governed by an ultraviolet (UV) fixed
point. A very satisfying example is given by asymptotic freedom of QCD
where the UV fixed point is non-interacting. In this talk, I discuss the
existence of interacting UV fixed points in various quantum field theories,
in particular in four dimensions, both with and without gravity. Implications
for particle physics are also evaluated.
It is commonly believed that for a quantum field theory to be fundamental,
its high-energy behaviour must be governed by an ultraviolet (UV) fixed
point. A very satisfying example is given by asymptotic freedom of QCD
where the UV fixed point is non-interacting. In this talk, I discuss the
existence of interacting UV fixed points in various quantum field theories,
in particular in four dimensions, both with and without gravity. Implications
for particle physics are also evaluated.
Posted by: QMW
Wed
26 Nov 2014
Applying Aristotelean logic to Double Field Theory
📍 London
George Papadopoulos
(King's College)
Abstract:
Is there a consistent patching for double manifolds? I shall demonstrate that the solution of the strong section condition leads to exact 3-form field strengths. I shall also prove that the consistency of the examples presented so far depends on the choice of the atlas, and so they are not general covariant. Then I shall suggest a new construction which resolves some of the puzzles and possibly specifies the appropriate spaces up to homotopy.
Is there a consistent patching for double manifolds? I shall demonstrate that the solution of the strong section condition leads to exact 3-form field strengths. I shall also prove that the consistency of the examples presented so far depends on the choice of the atlas, and so they are not general covariant. Then I shall suggest a new construction which resolves some of the puzzles and possibly specifies the appropriate spaces up to homotopy.
Posted by: KCL
Wed
26 Nov 2014
Effective actions for fluids from holography and the membrane paradigm
Natalia Pinzani Fokeeva
(Amsterdam)
Abstract:
It is widely believed that hydrodynamics is the low energy effective theory of any quantum field theory. In this talk I will derive the local low energy effective action for uncharged dissipationless conformal fluids through holography. This can be achieved by solving a double-Dirichlet problem for linearised gravitational perturbations between the conformal boundary of a (4+1)-dimensional AdS-black brane background and a stretched horizon. Interestingly dissipationless fluid dynamics is captured by Goldstone bosons of the broken symmetries by the classical solution ending on the second boundary. I will discuss how the effective action approach might be inconsistent unless there is a coupling to a dissipative dynamical IR sector which for simplicity can be replaced by a membrane paradigm-like boundary condition on a stretched horizon and I will also comment on the limits of validity of this simplification.
It is widely believed that hydrodynamics is the low energy effective theory of any quantum field theory. In this talk I will derive the local low energy effective action for uncharged dissipationless conformal fluids through holography. This can be achieved by solving a double-Dirichlet problem for linearised gravitational perturbations between the conformal boundary of a (4+1)-dimensional AdS-black brane background and a stretched horizon. Interestingly dissipationless fluid dynamics is captured by Goldstone bosons of the broken symmetries by the classical solution ending on the second boundary. I will discuss how the effective action approach might be inconsistent unless there is a coupling to a dissipative dynamical IR sector which for simplicity can be replaced by a membrane paradigm-like boundary condition on a stretched horizon and I will also comment on the limits of validity of this simplification.
Posted by: IC
Wed
26 Nov 2014
Three-dimensional black holes and descendants
Carmen Li
(Edinburgh)
Abstract:
We determine the most general three-dimensional vacuum spacetime with a negative cosmological constant containing a non-singular Killing horizon. We show that the general solution with a spatially compact horizon possesses a second commuting Killing field and deduce that it must be related to the BTZ black hole (or its near-horizon geometry) by a diffeomorphism. We show there is a general class of asymptotically AdS_3 extreme black holes with arbitrary charges with respect to one of the asymptotic-symmetry Virasoro algebras and vanishing charges with respect to the other. We interpret these as descendants of the extreme BTZ black hole.
We determine the most general three-dimensional vacuum spacetime with a negative cosmological constant containing a non-singular Killing horizon. We show that the general solution with a spatially compact horizon possesses a second commuting Killing field and deduce that it must be related to the BTZ black hole (or its near-horizon geometry) by a diffeomorphism. We show there is a general class of asymptotically AdS_3 extreme black holes with arbitrary charges with respect to one of the asymptotic-symmetry Virasoro algebras and vanishing charges with respect to the other. We interpret these as descendants of the extreme BTZ black hole.
Posted by: IC
Tue
25 Nov 2014
Massive Higher-Spin Gravities in 3d unfolded
📍 London
Dmitry Ponomarev
(LMU (Munich))
Abstract:
We classify the possible linear unfolded equations for propagating
bosonic higher-spin tensor fields in AdS_3 backgrounds. Doing this
we reproduce the existing topologically massive and new topologically
massive (higher)-spin systems whose content we clarify. We find systems
that generalise various critical gravities to higher-spins.
We classify the possible linear unfolded equations for propagating
bosonic higher-spin tensor fields in AdS_3 backgrounds. Doing this
we reproduce the existing topologically massive and new topologically
massive (higher)-spin systems whose content we clarify. We find systems
that generalise various critical gravities to higher-spins.
Posted by: KCL
Tue
25 Nov 2014
Resolving the Structure of Black Holes
Nicholas Warner
(IPhT, Saclay and Southern California U.)
Wed
19 Nov 2014
Higher spins, entanglement and Wilson lines
📍 London
Juan Jottar
(ETH (Zurich))
Abstract:
We discuss entanglement and Renyi entropies in two-dimensional conformal field theories with extended symmetry algebras of W-type, in the semiclassical (large-c) limit. From the CFT perspective, the computation of these non-local observables involves the study of semiclassical conformal blocks in theories with additional conserved currents beyond the stress tensor. From an AdS perspective, the problem can be tackled using recent holographic proposals in terms of Wilson lines in the dual three-dimensional higher spin theories. We discuss non-trivial examples exhibiting the agreement between bulk and boundary computations.
We discuss entanglement and Renyi entropies in two-dimensional conformal field theories with extended symmetry algebras of W-type, in the semiclassical (large-c) limit. From the CFT perspective, the computation of these non-local observables involves the study of semiclassical conformal blocks in theories with additional conserved currents beyond the stress tensor. From an AdS perspective, the problem can be tackled using recent holographic proposals in terms of Wilson lines in the dual three-dimensional higher spin theories. We discuss non-trivial examples exhibiting the agreement between bulk and boundary computations.
Posted by: KCL
Wed
19 Nov 2014
Striped phase in holographic d-wave superconductor
Alexander Krikun
(Nordita)
Abstract:
In its most general formulation the gauge/string duality may be used to build models of various strongly coupled systems in condensed matter. One of these is high-temperature d-wave superconductor. The holographic model of d-wave superconductor includes the dynamics of spin-2 charged field on top of the curved AdS geometry. In the probe approximation the model may be formulated consistently and exhibits a number of interesting physical phenomena. The important task is to classify all possible ground states of the model, which will correspond to the various phases of the dual system, and study the resulting phase diagram. In this talk I will discuss the recently found ground state which exhibits the stripes of charge density, violates the translation symmetry spontaneously and may be associated with the pseudogap state in high-Tc superconductors.
In its most general formulation the gauge/string duality may be used to build models of various strongly coupled systems in condensed matter. One of these is high-temperature d-wave superconductor. The holographic model of d-wave superconductor includes the dynamics of spin-2 charged field on top of the curved AdS geometry. In the probe approximation the model may be formulated consistently and exhibits a number of interesting physical phenomena. The important task is to classify all possible ground states of the model, which will correspond to the various phases of the dual system, and study the resulting phase diagram. In this talk I will discuss the recently found ground state which exhibits the stripes of charge density, violates the translation symmetry spontaneously and may be associated with the pseudogap state in high-Tc superconductors.
Posted by: IC
Wed
19 Nov 2014
Form factors, Anomalous Dimensions and the Dilatation Operator of N=4 SYM Theory
Matthias Wilhelm
(Humboldt)
Abstract:
We study the form factor of a generic gauge-invariant local
composite operator in N=4 SYM theory. At tree-level and for a minimal
number of external fields, the form factor exactly realises the
spin-chain picture of N=4 SYM theory in the language of scattering
amplitudes. Via generalised unitarity, we obtain the cut-constructible
part of the one-loop correction to the minimal form factor of a
generic operator. Its UV divergence yields the complete one-loop
dilatation operator of the theory. We also compute the complete
two-loop correction to the two-point form factor of the Konishi
operator via unitarity and obtain the two-loop Konishi anomalous
dimensions from it. For the Konishi operator as well as other
non-protected operators, important subtleties arise which require an
extension of the method of unitarity.
Moreover, since the inclusion of non-protected operators into the
action renders it formally non-supersymmetric, the form factors of
these operators share many features with quantities in QCD, such as
the occurrence of rational terms. The talk is based on the recent
works 1410.6309 and 1410.8485.
We study the form factor of a generic gauge-invariant local
composite operator in N=4 SYM theory. At tree-level and for a minimal
number of external fields, the form factor exactly realises the
spin-chain picture of N=4 SYM theory in the language of scattering
amplitudes. Via generalised unitarity, we obtain the cut-constructible
part of the one-loop correction to the minimal form factor of a
generic operator. Its UV divergence yields the complete one-loop
dilatation operator of the theory. We also compute the complete
two-loop correction to the two-point form factor of the Konishi
operator via unitarity and obtain the two-loop Konishi anomalous
dimensions from it. For the Konishi operator as well as other
non-protected operators, important subtleties arise which require an
extension of the method of unitarity.
Moreover, since the inclusion of non-protected operators into the
action renders it formally non-supersymmetric, the form factors of
these operators share many features with quantities in QCD, such as
the occurrence of rational terms. The talk is based on the recent
works 1410.6309 and 1410.8485.
Posted by: QMW
Tue
18 Nov 2014
tba
Tomasz Lukowski
(Oxford)
Thu
13 Nov 2014
Holography, Probe Branes and Isoperimetric Inequalities
Frank Ferrari
(Brussels U.)
Abstract:
In many instances of holographic correspondences between a d dimensional boundary theory and a d+1 dimensional bulk, a simple argument in the boundary theory implies that there must exist a direct relation between the on-shell Euclidean gravitational bulk action and the on-shell Euclidean action of a (d-1)-brane probing the bulk geometry. This relation is crucial for the consistency of holography but puzzling from the bulk perspective. We provide a full bulk derivation in the case of pure gravity.
A central role is played by a non-trivial isoperimetric inequality that must be satisfied in a large class of Poincaré-Einstein spaces. Remarkably, this inequality follows from a theorem by John Lee.
In many instances of holographic correspondences between a d dimensional boundary theory and a d+1 dimensional bulk, a simple argument in the boundary theory implies that there must exist a direct relation between the on-shell Euclidean gravitational bulk action and the on-shell Euclidean action of a (d-1)-brane probing the bulk geometry. This relation is crucial for the consistency of holography but puzzling from the bulk perspective. We provide a full bulk derivation in the case of pure gravity.
A central role is played by a non-trivial isoperimetric inequality that must be satisfied in a large class of Poincaré-Einstein spaces. Remarkably, this inequality follows from a theorem by John Lee.
Posted by: QMW
Wed
12 Nov 2014
The quantum theory of fluids
📍 London
Ben Gripaios
(Cambridge Cavendish)
Abstract:
I discuss the quantization of a perfect fluid. This differs from textbook QFT, because of the presence of vortex modes, which map to an infinite collection of quantum mechanical free particles rather than harmonic oscillators. As a result, there is no Fock space and no S-matrix. I argue that there exists, nevertheless, a consistent effective field theory description, valid at large distances and times.
I discuss the quantization of a perfect fluid. This differs from textbook QFT, because of the presence of vortex modes, which map to an infinite collection of quantum mechanical free particles rather than harmonic oscillators. As a result, there is no Fock space and no S-matrix. I argue that there exists, nevertheless, a consistent effective field theory description, valid at large distances and times.
Posted by: KCL
Wed
12 Nov 2014
Galaxy Clusters as Tele-ALP-scopes
📍 London
Joe Conlon
(Oxford)
Abstract:
Galaxy clusters are the most efficient convertors of axion-like particles to photons in the universe.
I discuss the physics and phenomenology of ALPs, and describe their astrophysical implications, with particular reference to the
recently observed 3.5 keV X-ray line that is a candidate for a dark matter decay line.
Galaxy clusters are the most efficient convertors of axion-like particles to photons in the universe.
I discuss the physics and phenomenology of ALPs, and describe their astrophysical implications, with particular reference to the
recently observed 3.5 keV X-ray line that is a candidate for a dark matter decay line.
Posted by: KCL
Tue
11 Nov 2014
String Compactifications, Dark Radiation and a 0.1-1 keV Cosmic Axion Background
Joseph Conlon
(Oxford U., Theor. Phys.)
Tue
11 Nov 2014
Harmony of scattering amplitudes
Gabriele Travaglini
(QMUL)
Thu
6 Nov 2014
A universal correction to higher spin entanglement entropy
Michael Ferlaino
(Swansea)
Abstract:
Within the context of the duality between higher spin gravitational theories and a semi-
classical limit of WN minimal models, we consider 2D CFTs with W1 symmetry at nite
temperature, deformed by the presence of a chemical potential for the spin{three current. As
a perturbative expansion in the chemical potential, we compute the Renyi and entanglement
entropies for a single interval. The leading correction is universal and matches the holographic
result, based on Wilson line functionals, obtained from the higher spin gravitational dual.
Within the context of the duality between higher spin gravitational theories and a semi-
classical limit of WN minimal models, we consider 2D CFTs with W1 symmetry at nite
temperature, deformed by the presence of a chemical potential for the spin{three current. As
a perturbative expansion in the chemical potential, we compute the Renyi and entanglement
entropies for a single interval. The leading correction is universal and matches the holographic
result, based on Wilson line functionals, obtained from the higher spin gravitational dual.
Posted by: QMW
Wed
5 Nov 2014
F-theory on singular spaces
📍 London
Andres Collinucci
(ULB, Brussels)
Abstract:
F-theory paints a beautiful picture that relates gauge theories to purely geometric information, whereby the Dynkin diagrams of gauge groups come to life as 2-cycles of internal spaces. The caveat is that, such spaces are necessarily singular, and treating them sensibly requires resolving or deforming the singularities.
Recently, my collaborator R. Savelli and I have proposed a new strategy that allows one to deal with singular spaces directly. It is based on Eisenbud’s so-called matrix factorisations. This remarkably simple concept has very deep connections to the mathematics of singularities.
In this talk, I will review the basic notions needed to formulate the issues, assuming only standard knowledge of string theory. Then, after introducing our proposal, I will show examples of its applications, such as computations of chiral spectra for bound states of 7-branes.
F-theory paints a beautiful picture that relates gauge theories to purely geometric information, whereby the Dynkin diagrams of gauge groups come to life as 2-cycles of internal spaces. The caveat is that, such spaces are necessarily singular, and treating them sensibly requires resolving or deforming the singularities.
Recently, my collaborator R. Savelli and I have proposed a new strategy that allows one to deal with singular spaces directly. It is based on Eisenbud’s so-called matrix factorisations. This remarkably simple concept has very deep connections to the mathematics of singularities.
In this talk, I will review the basic notions needed to formulate the issues, assuming only standard knowledge of string theory. Then, after introducing our proposal, I will show examples of its applications, such as computations of chiral spectra for bound states of 7-branes.
Posted by: KCL
Wed
5 Nov 2014
Gerbes on the Lattice
Ron Reid-Edwards
(Hull)
Abstract:
Abelian gerbes play a ubiquitous role in string and supergravity theories. It is conjectured that non-abelian gerbe theories exist, but a satisfactory explicit construction of such a theory has not yet been achieved. Inspired by the possibility that a non-abelian theory of gerbes may be possible on non-conventional spacetimes, I will consider a toy model on a lattice that allows one to make some progress in this problem. In this talk, I will show how abelian gerbe theories may be described naturally on the lattice. I will outline a non-abelian generalisation and show how, under dimensional reduction, such theories give rise to lattice Yang-Mills.
Abelian gerbes play a ubiquitous role in string and supergravity theories. It is conjectured that non-abelian gerbe theories exist, but a satisfactory explicit construction of such a theory has not yet been achieved. Inspired by the possibility that a non-abelian theory of gerbes may be possible on non-conventional spacetimes, I will consider a toy model on a lattice that allows one to make some progress in this problem. In this talk, I will show how abelian gerbe theories may be described naturally on the lattice. I will outline a non-abelian generalisation and show how, under dimensional reduction, such theories give rise to lattice Yang-Mills.
Posted by: IC
Wed
5 Nov 2014
Enhanced ultraviolet cancellations in supergravity theories
Zvi Bern
(UCLA)
October 2014
Wed
29 Oct 2014
Exact Results in SUSY: Lecture 4
Brian Wecht
(QMUL)
Abstract:
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
Posted by: QMW
Wed
29 Oct 2014
Yangian symmetry of smooth super-Wilson loops in planar N=4 super-Yang-Mills
📍 London
Cristian Vergu
(King's College)
Abstract:
Light-like polygonal super-Wilson loops are dual to scattering
amplitudes in planar N=4 super-Yang-Mills and enjoy an
infinite-dimensional Yangian symmetry which extends the superconformal
symmetry. However, this symmetry is anomalous. In this talk we will
describe a super-Wilson loop on a smooth contour, which is free of
UV divergences and on which the superconformal symmetry operators are
not anomalous. We also study the action of level one Yangian generators
on the one-loop expectation value of this super-Wilson loop. [This is
work in progress with N.Beisert, D.Muller and J.Plefka]
Light-like polygonal super-Wilson loops are dual to scattering
amplitudes in planar N=4 super-Yang-Mills and enjoy an
infinite-dimensional Yangian symmetry which extends the superconformal
symmetry. However, this symmetry is anomalous. In this talk we will
describe a super-Wilson loop on a smooth contour, which is free of
UV divergences and on which the superconformal symmetry operators are
not anomalous. We also study the action of level one Yangian generators
on the one-loop expectation value of this super-Wilson loop. [This is
work in progress with N.Beisert, D.Muller and J.Plefka]
Posted by: KCL
Wed
29 Oct 2014
From higher spins to strings: a constructive approach
Massimo Taronna
(Potsdam)
Abstract:
Starting from some examples, I will review various implications of classical consistency that have played a key role in the context of higher-spin theories (Vasiliev's equations) and holography. I will then review the current understanding higher-spin interactions involving totally-symmetric higher-spin fields and the associated classification of higher-spin algebras generalizing Coleman-Mandula theorem in the context of AdS/CFT. Finally, I will discuss the extension of this analysis to massive higher spins, towards a new understanding of string theory.
Starting from some examples, I will review various implications of classical consistency that have played a key role in the context of higher-spin theories (Vasiliev's equations) and holography. I will then review the current understanding higher-spin interactions involving totally-symmetric higher-spin fields and the associated classification of higher-spin algebras generalizing Coleman-Mandula theorem in the context of AdS/CFT. Finally, I will discuss the extension of this analysis to massive higher spins, towards a new understanding of string theory.
Posted by: IC
Wed
29 Oct 2014
3d and 5d SUSY partition functions as q-deformed CFT correlators
Fabrizio Nieri
(Surrey)
Abstract:
In recent years, due to the method of supersymmetric localization, many exact results have been achieved in the study of supersymmetric gauge theories on compact spaces of various dimension and topology, leading to the discovery of surpraising structures. An important example is provided by the correspondence introduced by Alday, Gaiotto and Tachikawa, relating the partition functions of a large class of supersymmetric gauge theories on S4 and S2 to correlators in Liouville CFT. In this talk, I will explain how this picture can be lifted to higher dimensional gauge theories via the correspondence of partition functions on S5, S4xS1, S3 and S2xS1 to correlators in theories whose underlying symmetry is given by a quantum deformation of the Virasoro algebra. In particular, I will discuss how 3-point functions can be derived by the bootstrap approach and used to define this novel class of q-deformed CFTs. I will also discuss some aspects related to integrable structures in these models, such as reflection coefficients, as well as possible generalisation.
In recent years, due to the method of supersymmetric localization, many exact results have been achieved in the study of supersymmetric gauge theories on compact spaces of various dimension and topology, leading to the discovery of surpraising structures. An important example is provided by the correspondence introduced by Alday, Gaiotto and Tachikawa, relating the partition functions of a large class of supersymmetric gauge theories on S4 and S2 to correlators in Liouville CFT. In this talk, I will explain how this picture can be lifted to higher dimensional gauge theories via the correspondence of partition functions on S5, S4xS1, S3 and S2xS1 to correlators in theories whose underlying symmetry is given by a quantum deformation of the Virasoro algebra. In particular, I will discuss how 3-point functions can be derived by the bootstrap approach and used to define this novel class of q-deformed CFTs. I will also discuss some aspects related to integrable structures in these models, such as reflection coefficients, as well as possible generalisation.
Posted by: QMW
Mon
27 Oct 2014
Exact Results in SUSY: Lecture 3
Brian Wecht
(QMUL)
Abstract:
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
Posted by: QMW
Thu
23 Oct 2014
Coexistence of generalized fluxes and their exotic brane sources
Athanasios Chatzistavrakidis
(Hannover)
Abstract:
In recent years there is a growing interest in unconventional string backgrounds with non-geometric fluxes. The latter often appear after
repeated T-dualities on known backgrounds. However, a very interesting question regards whether these fluxes can coexist in generalized geometries
without a geometric dual. In this talk we address this question and we show that in principle there exist such geometries where all types of fluxes coexist.
Our strategy consists in using generalized geometry and in particular Dirac structures, which are subbundles of the generalized tangent bundle where the
Courant bracket is associative and field strengths transform tensorially. We study the mathematical description of fluxes on Dirac structures and then combine the
latter into Courant algebroids that describe multi-flux geometries. Furthermore we discuss the sources of non-geometric fluxes, which are heavy extended objects
known as exotic branes. These branes exhibit a wide range of world volume dimensions, tension scalings and monodromy properties, and we argue that they couple to
certain mixed symmetry tensors, which are exotic magnetic duals of the supergravity background fields.
In recent years there is a growing interest in unconventional string backgrounds with non-geometric fluxes. The latter often appear after
repeated T-dualities on known backgrounds. However, a very interesting question regards whether these fluxes can coexist in generalized geometries
without a geometric dual. In this talk we address this question and we show that in principle there exist such geometries where all types of fluxes coexist.
Our strategy consists in using generalized geometry and in particular Dirac structures, which are subbundles of the generalized tangent bundle where the
Courant bracket is associative and field strengths transform tensorially. We study the mathematical description of fluxes on Dirac structures and then combine the
latter into Courant algebroids that describe multi-flux geometries. Furthermore we discuss the sources of non-geometric fluxes, which are heavy extended objects
known as exotic branes. These branes exhibit a wide range of world volume dimensions, tension scalings and monodromy properties, and we argue that they couple to
certain mixed symmetry tensors, which are exotic magnetic duals of the supergravity background fields.
Posted by: QMW
Wed
22 Oct 2014
Exact Results in SUSY: Lecture 2
Brian Wecht
(QMUL)
Abstract:
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
In this series of 4-5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
Posted by: QMW
Wed
22 Oct 2014
Permutation orbifolds and holography
📍 London
Mukund Rangamani
(Durham )
Abstract:
CFTs at large central charge display some universal features which can be inferred from holography. Using these as a guide one can obtain some necessary conditions for a given CFT to admit a classical gravity dual. I will describe attempts to construct a large class of CFTs satisfying these conditions exploiting some technology of permutation orbifolds. Time permitting I will also outline some tests for the sufficiency of these conditions.
CFTs at large central charge display some universal features which can be inferred from holography. Using these as a guide one can obtain some necessary conditions for a given CFT to admit a classical gravity dual. I will describe attempts to construct a large class of CFTs satisfying these conditions exploiting some technology of permutation orbifolds. Time permitting I will also outline some tests for the sufficiency of these conditions.
Posted by: KCL
Wed
22 Oct 2014
Anatomy of the amplituhedron
Daniele Galloni
(Durham)
Abstract:
I will present this very recently proposed geometric object, conjectured to give the N=4 SYM scattering amplitudes at all orders, and illustrate the techniques used to fully explore its structure. In so doing I will give firm nontrivial evidence to the amplituhedron conjecture.
I will present this very recently proposed geometric object, conjectured to give the N=4 SYM scattering amplitudes at all orders, and illustrate the techniques used to fully explore its structure. In so doing I will give firm nontrivial evidence to the amplituhedron conjecture.
Posted by: IC
Wed
22 Oct 2014
Aspects of Higher Spin Symmetries in Various Dimensions
Karan Govil
(U. Penn)
Abstract:
The algebras of higher spin symmetries in conformal field theories in four and six dimensions are not unique and have a richer structure due to the existence of infinite short multiplets besides the usual scalar and spinor. We will focus on recent results that show there exists a one parameter family (continuous of d=4 and discrete for d=6) of higher spin algebras and superalgebras, and give an explicit unitary representation for these algebras using quasiconformal methods. We will also discuss the implications of these results for the AdS5/CFT4 and AdS7/CFT6 higher spin holography.
The algebras of higher spin symmetries in conformal field theories in four and six dimensions are not unique and have a richer structure due to the existence of infinite short multiplets besides the usual scalar and spinor. We will focus on recent results that show there exists a one parameter family (continuous of d=4 and discrete for d=6) of higher spin algebras and superalgebras, and give an explicit unitary representation for these algebras using quasiconformal methods. We will also discuss the implications of these results for the AdS5/CFT4 and AdS7/CFT6 higher spin holography.
Posted by: IC
Wed
22 Oct 2014
Non-perturbative elementary particle mass generation
Giancarlo Rossi
(INFN Rome)
Abstract:
Taking inspiration from lattice QCD data, we argue that a finite
non-perturbative mass contribution for quarks is generated as another consequence of
the dynamical phenomenon of spontaneous chiral symmetry breaking, which is in turn
triggered by the explicitly breaking of chiral symmetry induced by the critical
Wilson term in the action. In pure lattice QCD this mass term cannot be
separated from the unavoidably associated linearly divergent contribution.
However, if QCD is enlarged to a theory where also a scalar field is present,
coupled to a doublet of SU(2) fermions via a Yukawa and a Wilson-like term,
then in the phase where the scalar field takes a non-vanishing expectation
value, a dynamically generated and "naturally" light fermion mass (numerically
unrelated to the expectation value of the scalar field) is conjectured to
emerge at a critical value of the Yukawa coupling where the symmetry of the
model is maximally enhanced. Masses dynamically generated in this way display a
natural hierarchy according to which the stronger is the strongest of the
interactions the fermion is subjected to the larger is its mass.
Taking inspiration from lattice QCD data, we argue that a finite
non-perturbative mass contribution for quarks is generated as another consequence of
the dynamical phenomenon of spontaneous chiral symmetry breaking, which is in turn
triggered by the explicitly breaking of chiral symmetry induced by the critical
Wilson term in the action. In pure lattice QCD this mass term cannot be
separated from the unavoidably associated linearly divergent contribution.
However, if QCD is enlarged to a theory where also a scalar field is present,
coupled to a doublet of SU(2) fermions via a Yukawa and a Wilson-like term,
then in the phase where the scalar field takes a non-vanishing expectation
value, a dynamically generated and "naturally" light fermion mass (numerically
unrelated to the expectation value of the scalar field) is conjectured to
emerge at a critical value of the Yukawa coupling where the symmetry of the
model is maximally enhanced. Masses dynamically generated in this way display a
natural hierarchy according to which the stronger is the strongest of the
interactions the fermion is subjected to the larger is its mass.
Posted by: QMW
Tue
21 Oct 2014
Aspects of Higher Spin Symmetries in Various Dimensions
📍 London
Karan Govil
(Pennsylvania State Universiy)
Abstract:
The algebras of higher spin symmetries in conformal field theories in four and six dimensions are not unique and have a richer structure due to the existence of infinite short multiplets besides the usual scalar and spinor. We will focus on recent results that show there exists a one parameter family (continuous of d=4 and discrete for d=6) of higher spin algebras and superalgebras, and give an explicit unitary representation for these algebras using quasiconformal methods. We will also discuss the implications of these results for the AdS5/CFT4 and AdS7/CFT6 higher spin holography.
The algebras of higher spin symmetries in conformal field theories in four and six dimensions are not unique and have a richer structure due to the existence of infinite short multiplets besides the usual scalar and spinor. We will focus on recent results that show there exists a one parameter family (continuous of d=4 and discrete for d=6) of higher spin algebras and superalgebras, and give an explicit unitary representation for these algebras using quasiconformal methods. We will also discuss the implications of these results for the AdS5/CFT4 and AdS7/CFT6 higher spin holography.
Posted by: KCL
Mon
20 Oct 2014
Exact Results in SUSY: Lecture 1
Brian Wecht
(QMUL)
Abstract:
In this series of 4 or 5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
In this series of 4 or 5 2-hour lectures, I'll describe some of the powerful exact results that one can achieve in supersymmetric theories. The topics will be as follows:
Lecture 1: Non-Renormalization Theorems
Lecture 2: Classical and Quantum Moduli Spaces
Lecture 3: Superconformal Field Theories and Seiberg Duality
Lecture 4: Central Charges, a-maximization, and the a-theorem
Lecture 5 (if it happens): Brane Tilings and Dimers
Posted by: QMW
Thu
16 Oct 2014
On the ten-/eleven-dimensional uplift of STU-models
Giuseppe Dibitetto
(Uppsala)
Abstract:
We consider two classes of minimally supersymmetric STU-models in four dimensions motivated by their (conjectured) origin, respectively, from reductions of massive type IIA string theory on SU(3)-structure manifolds and M-theory on G2-structure. In both cases, we identify the geometric origin of the moduli ?fields and derive the dictionary between metric fluxes and torsion classes. The matching between the expression of the Ricci scalar and the metric flux-induced scalar potential works in any point of moduli space and regardless of whether or not Jacobi constraints have been imposed on
the metric flux components. Finally, we provide the ten- or eleven-dimensional uplift of the aforementioned supergravity models by showing the equivalence between higher-dimensional and four-dimensional equations of motion.
We consider two classes of minimally supersymmetric STU-models in four dimensions motivated by their (conjectured) origin, respectively, from reductions of massive type IIA string theory on SU(3)-structure manifolds and M-theory on G2-structure. In both cases, we identify the geometric origin of the moduli ?fields and derive the dictionary between metric fluxes and torsion classes. The matching between the expression of the Ricci scalar and the metric flux-induced scalar potential works in any point of moduli space and regardless of whether or not Jacobi constraints have been imposed on
the metric flux components. Finally, we provide the ten- or eleven-dimensional uplift of the aforementioned supergravity models by showing the equivalence between higher-dimensional and four-dimensional equations of motion.
Posted by: QMW
Wed
15 Oct 2014
Coulomb branch and the moduli space of instantons
📍 London
Stefano Cremonesi
(King's College)
Abstract:
I will explain how to compute the Hilbert series that counts chiral operators parametrising the Coulomb branch of the moduli space of vacua of three-dimensional N=4 supersymmetric gauge theories. The formula has applications to Physics, such as to the study of infrared dualities in three dimensions and of string backgrounds with eight supercharges, as well as to Mathematics, where it provides a new way to characterise HyperKaehler cones as algebraic varieties.
I will then show how the Coulomb branch of certain 3d N=4 generalised quiver gauge theories can be used to compute the Hilbert series of the moduli space of k G-instantons, for any simple Lie group G. The construction is alternative to the ADHM construction that is only available for classical groups G.
I will explain how to compute the Hilbert series that counts chiral operators parametrising the Coulomb branch of the moduli space of vacua of three-dimensional N=4 supersymmetric gauge theories. The formula has applications to Physics, such as to the study of infrared dualities in three dimensions and of string backgrounds with eight supercharges, as well as to Mathematics, where it provides a new way to characterise HyperKaehler cones as algebraic varieties.
I will then show how the Coulomb branch of certain 3d N=4 generalised quiver gauge theories can be used to compute the Hilbert series of the moduli space of k G-instantons, for any simple Lie group G. The construction is alternative to the ADHM construction that is only available for classical groups G.
Posted by: KCL
Wed
15 Oct 2014
A universal correction to higher spin entanglement entropy
Michael Ferlaino
(Swansea)
Abstract:
Within the context of the duality between higher spin gravitational theories and a semi-
classical limit of W_N minimal models, we consider 2D CFTs with W_∞ symmetry at finite
temperature, deformed by the presence of a chemical potential for the spin–three current. As a perturbative expansion in the chemical potential, we compute the Renyi and entanglement entropies for a single interval. The leading correction is universal and matches the holographic result, based on Wilson line functionals, obtained from the higher spin gravitational dual.
Within the context of the duality between higher spin gravitational theories and a semi-
classical limit of W_N minimal models, we consider 2D CFTs with W_∞ symmetry at finite
temperature, deformed by the presence of a chemical potential for the spin–three current. As a perturbative expansion in the chemical potential, we compute the Renyi and entanglement entropies for a single interval. The leading correction is universal and matches the holographic result, based on Wilson line functionals, obtained from the higher spin gravitational dual.
Posted by: IC
Wed
15 Oct 2014
3d and 5d gauge theory partition functions as q-deformed CFT correlators
Fabrizio Nieri
(Surrey)
Abstract:
In recent years, due to the method of supersymmetric localization, many exact results have been achieved in the study of supersymmetric gauge theories on compact spaces of various dimension and topology, leading to the discovery of surpraising structures. An important example is provided by the correspondence introduced by Alday, Gaiotto and Tachikawa, relating the partition functions of a large class of supersymmetric gauge theories on S4 and S2 to correlators in Liouville CFT. In this talk, I will explain how this picture can be lifted to higher dimensional gauge theories via the correspondence of partition functions on S5, S4xS1, S3 and S2xS1 to correlators in theories whose underlying symmetry is given by a quantum deformation of the Virasoro algebra. In particular, I will discuss how 3-point functions can be derived by the bootstrap approach and used to define this novel class of q-deformed CFTs. I will also discuss some aspects related to integrable structures in these models, such as reflection coefficients, as well as possible generalisation.
In recent years, due to the method of supersymmetric localization, many exact results have been achieved in the study of supersymmetric gauge theories on compact spaces of various dimension and topology, leading to the discovery of surpraising structures. An important example is provided by the correspondence introduced by Alday, Gaiotto and Tachikawa, relating the partition functions of a large class of supersymmetric gauge theories on S4 and S2 to correlators in Liouville CFT. In this talk, I will explain how this picture can be lifted to higher dimensional gauge theories via the correspondence of partition functions on S5, S4xS1, S3 and S2xS1 to correlators in theories whose underlying symmetry is given by a quantum deformation of the Virasoro algebra. In particular, I will discuss how 3-point functions can be derived by the bootstrap approach and used to define this novel class of q-deformed CFTs. I will also discuss some aspects related to integrable structures in these models, such as reflection coefficients, as well as possible generalisation.
Posted by: IC
Wed
15 Oct 2014
A new gravity-gauge dictionary
Silvia Nagy
(Imperial College London)
Abstract:
The idea of writing supergravity as a double copy of super Yang-Mills theories has proved a fruitful one, most notably in the context of scattering amplitudes. I will explore this idea of "squaring" at a fundamental level to explain how the symmetries of the former(both local and global) can be written as a double copy of the latter. I will show how the gravitational symmetries of general covariance, p-form gauge invariance, local Lorentz invariance and local supersymmetry are obtained from the flat space Yang-Mills symmetries of local gauge invariance and global super-Poincare. We give a gravity-gauge dictionary by convoluting fields and parameters. At the global level, I will explain how the coset groups of supergravity can be derived from the global R-symmetries of the SYM multiplets, via the 4 division algebras:reals, complexes, quaternions and octonions. Finally I will explore some intriguing possible applications of our dictonary.
The idea of writing supergravity as a double copy of super Yang-Mills theories has proved a fruitful one, most notably in the context of scattering amplitudes. I will explore this idea of "squaring" at a fundamental level to explain how the symmetries of the former(both local and global) can be written as a double copy of the latter. I will show how the gravitational symmetries of general covariance, p-form gauge invariance, local Lorentz invariance and local supersymmetry are obtained from the flat space Yang-Mills symmetries of local gauge invariance and global super-Poincare. We give a gravity-gauge dictionary by convoluting fields and parameters. At the global level, I will explain how the coset groups of supergravity can be derived from the global R-symmetries of the SYM multiplets, via the 4 division algebras:reals, complexes, quaternions and octonions. Finally I will explore some intriguing possible applications of our dictonary.
Posted by: QMW
Tue
14 Oct 2014
Superalgebras and supersymmetry in low dimensional lattice systems
Sarben Sarkar
(King's College London)
Abstract:
It will be shown how supersymmetry and superalgebras arise in lattice models both in one and higher dimensions. Examples using correlated fermions and bosons will be primarily used. Some of the examples will have associated superalgebras and others will have supersymmetry more commonly used in field theory. Some aspects of continuum limits will also be touched upon.
It will be shown how supersymmetry and superalgebras arise in lattice models both in one and higher dimensions. Examples using correlated fermions and bosons will be primarily used. Some of the examples will have associated superalgebras and others will have supersymmetry more commonly used in field theory. Some aspects of continuum limits will also be touched upon.
Posted by: IC
Mon
13 Oct 2014
Holographic stringy hadrons
Sonnenschein Jacob
(Tel Aviv)
Abstract:
I will show that the non-stringy holographic description of hadrons, namely the one based on fields that reside on the bulk and flavor branes, fails to reproduce the hadronic spectra. I will briefly review the stringy duals of Wilson loops and determine the sufficient conditions of confining backgrounds. I will show that the latter are also the requirements for holographic stringy mesons to admit a Regge-like spectrum. I will determine a map between holographic stringy mesons and strings with massive endpoints in 4d flat space-time. Models of classical rotating strings with massive endpoints will be written down. I will discuss the (still unsolved) quantization of such systems. Fits of the models to mesonic data will be presented. A universal model that describes mesons of u,d,s,c quarks will be developed. Mesons with b quarks will also be fitted. I will describe the construction of stringy baryons in holography. I will show that the best description of baryons is in terms of a single string with a quark and a di-quark on its ends. I will present fits of such a model to the baryonic data. Finally I will describe the stringy decays of holographic hadrons.
I will show that the non-stringy holographic description of hadrons, namely the one based on fields that reside on the bulk and flavor branes, fails to reproduce the hadronic spectra. I will briefly review the stringy duals of Wilson loops and determine the sufficient conditions of confining backgrounds. I will show that the latter are also the requirements for holographic stringy mesons to admit a Regge-like spectrum. I will determine a map between holographic stringy mesons and strings with massive endpoints in 4d flat space-time. Models of classical rotating strings with massive endpoints will be written down. I will discuss the (still unsolved) quantization of such systems. Fits of the models to mesonic data will be presented. A universal model that describes mesons of u,d,s,c quarks will be developed. Mesons with b quarks will also be fitted. I will describe the construction of stringy baryons in holography. I will show that the best description of baryons is in terms of a single string with a quark and a di-quark on its ends. I will present fits of such a model to the baryonic data. Finally I will describe the stringy decays of holographic hadrons.
Posted by: IC
Thu
9 Oct 2014
Tensor Models and Renormalization
Joseph Ben Geloun
(AEI Golm)
Abstract:
A review will be provided on the renormalization program for
the so-called Tensor Models for Quantum Gravity. These are non local field theories extending both the matrix models, a successful framework in statistical mechanics
applied to 2D physics, and the Grosse-Wulkenhaar model in the matrix basis
arising in Noncommuting Neometry. We will emphasize the Multi-scale renormalization
but also report recent results on the Functional Renormalization Group Approach for these class of models.
A review will be provided on the renormalization program for
the so-called Tensor Models for Quantum Gravity. These are non local field theories extending both the matrix models, a successful framework in statistical mechanics
applied to 2D physics, and the Grosse-Wulkenhaar model in the matrix basis
arising in Noncommuting Neometry. We will emphasize the Multi-scale renormalization
but also report recent results on the Functional Renormalization Group Approach for these class of models.
Posted by: QMW
Wed
8 Oct 2014
Anatomy of the amplituhedron
Daniele Galloni
(Durham)
Abstract:
I will present this very recently proposed geometric object, conjectured to give the N=4 SYM scattering amplitudes at all orders , and illustrate the techniques used to fully explore its structure. In so doing I will give firm nontrivial evidence to the amplituhedron conjecture.
I will present this very recently proposed geometric object, conjectured to give the N=4 SYM scattering amplitudes at all orders , and illustrate the techniques used to fully explore its structure. In so doing I will give firm nontrivial evidence to the amplituhedron conjecture.
Posted by: QMW
Wed
8 Oct 2014
Short-range entangled phases and topology
Anton Kapustin
(SCGP)
Thu
2 Oct 2014
From gluons to gravitons in the soft limit
Chris White
(Glasgow)
Abstract:
It is well-known that infrared singularities arise in scattering amplitudes due to the emission of soft (low energy) gluons and / or gravitons. These are important for collider predictions, but also give us all-order insights into perturbation theory. This talk will review a number of recent developments in this area, such as: the structure of IR singularities in multiparton scattering amplitudes; the relationship between Yang-Mills theory and gravity in the soft limit; the classification of amplitudes beyond the soft approximation.
It is well-known that infrared singularities arise in scattering amplitudes due to the emission of soft (low energy) gluons and / or gravitons. These are important for collider predictions, but also give us all-order insights into perturbation theory. This talk will review a number of recent developments in this area, such as: the structure of IR singularities in multiparton scattering amplitudes; the relationship between Yang-Mills theory and gravity in the soft limit; the classification of amplitudes beyond the soft approximation.
Posted by: QMW
Wed
1 Oct 2014
Regge theory for correlation functions in CFTs
Vasco Goncalves
(U. do Porto)
Abstract:
In this talk we will try to motivate why the study of the Regge limit in a correlation function of a conformal field theory is interesting. We will review the results obtained in the past few years and present some on going work in phi^3 theory using skeleton expansion.
In this talk we will try to motivate why the study of the Regge limit in a correlation function of a conformal field theory is interesting. We will review the results obtained in the past few years and present some on going work in phi^3 theory using skeleton expansion.
Posted by: IC
September 2014
Mon
29 Sep 2014
Twistor Origin of the Superstring
Nathan Berkovits
(Sao Paulo)
Mon
29 Sep 2014
Scattering Amplitudes as a Flux Tube Gas
📍 London
Pedro Vieira
(Perimeter Institute)
Abstract:
TBA
TBA
Posted by: KCL
Thu
25 Sep 2014
Dyonic Ads Black Holes
Nick Halmagyi
(LPTHE)
Abstract:
I will discuss recent work constructing exact solution of
the general dyonic static BPS black hole in AdS4 within N=2
U(1)-gauged supergravity. For certain models these black holes have
lifts to M-theory they correspond to M2-branes wrapped on a Riemann
surface and rotating on S7
I will discuss recent work constructing exact solution of
the general dyonic static BPS black hole in AdS4 within N=2
U(1)-gauged supergravity. For certain models these black holes have
lifts to M-theory they correspond to M2-branes wrapped on a Riemann
surface and rotating on S7
Posted by: QMW