19th Itzykson Conference
Program
Venue: Claude Bloch conference room - IPhT CEA-Saclay
Information regarding bus schedule
| Tuesday June 10 |
Wednesday June 11 |
Thursday June 12 |
Friday June 13 |
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| 9h00 -- 9h30 | Registration/ Welcome address by director of IPhT | ||||
| 9h30 -- 10h30 | Britto | Henn | Dixon | Bern | |
| 10h30 -- 11h15 | Badger | Smirnov | Basso | Mastrolia | |
| 11h15 -- 11h45 | Coffee break | ||||
| 11h45 -- 12h30 | Green | Duhr | Caron-Huot | Bjerrum-Bohr | |
| 12h30 -- 13h00 | Penante | Yuan | Chicherin | Tourkine | |
| 13h00 -- 14h30 | Lunch | ||||
| 14h30 -- 15h15 | Larsen | Mafra | Sokatchev | Kazakov | |
| 15h15 -- 16h00 | Zhang | Maldacena | Huang | Roiban | |
| 16h00 -- 16h30 | Coffee break | ||||
| 16h30 -- 17h15 | Gardi | Gang Yang | Staudacher | Johansson | |
| 17h15 -- 18h00 | Vergu | Monteiro | Forini | Schomerus | |
| Dinner Restaurant La Gare La Gare - 19, chaussée de la Muette 75016 Paris |
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Titles of Talks
| Speaker | Title | Files |
| Simon Badger | D-dimensional integrand reduction methods for two loop QCD amplitudes
I will discuss recent developments for multi-loop integrand reduction methods and their applications in automated QCD computations. I will then present the application of these techniques to the computation of the five gluon amplitude with all positive helicities. | |
| Benjamin Basso | On the collinear limit of scattering amplitudes at strong coupling
Gluon scattering amplitudes are well known to be described by classical minimal surfaces in AdS5 at strong coupling in planar N=4 SYM theory. In this talk I will argue that the quantum fluctuations of these surfaces in the five-sphere S5 should not be underestimated and actually govern the amplitudes in the collinear limit. We will see that the right picture for the amplitudes in this regime is in terms of correlators of twist operators in the 2d O(6) sigma-model. This will lead us to conclude that scattering amplitudes receive a contribution from the sphere of the same magnitude as the minimal surface area. | |
| Zvi Bern | Recent Progress in Gravity Scattering Amplitudes.
I will review recent progress on gravity scattering amplitudes and then focus a few topics including soft and UV behavior of gravity scattering amplitudes and color-kinematics duality. | |
| N. Emil J. Bjerrum-Bohr | Scattering Equations and Amplitudes in String Theory
We discuss scattering equations for tree-level amplitudes in the context of string theory. As a result of the comparison we are led to consider a new dual model which agrees with the behavior of string theory in both the small and large alpha′ limit, and which can be solved algebraically on the surface of solutions to the scattering equations. We use the same idea to generalize scattering equations to amplitudes with fermions and any mixture of scalars, gluons and fermions. | |
| Ruth Britto | From cuts to coproducts of Feynman integrals
I discuss the relations between discontinuities and unitarity cuts of Feynman integrals, and propose that the cuts are computed by the Hopf algebra in the case of multiple polylogarithms. The relations are known in the case of a single standard unitarity cut, but are now generalized to multiple cuts. I comment on reconstructing the symbol and the full integral from its cuts. | |
| Simon Caron-Huot | Toying with bound states
I will discuss bound states in planar N=4 super Yang-Mills. Via the Higgs mechanism, this model includes massive particles, which attract to form hydrogen-like bound states. The not-so-obvious O(4) symmetry of the hydrogen atom, originating from the Laplace-Runge-Lenz vector in classical mechanics, acquires a vast extension in this model and becomes the dual conformal symmetry of N=4, shedding a new light on the latter. Using ideas from Regge theory, the spectral problem can be phrased as the calculation of the leading Regge trajectory, which was previously identified in this model with the angle-dependent cusp anomalous dimension. I will discuss the implications regarding the spectrum. | |
| Dmitrii Chicherin | Yang-Baxter
operators and scattering amplitudes in N=4 super-Yang-Mills theory
During past years unexpected symmetries have been revealed in the structure of perturbative scattering amplitudes. We formulate Yangian symmetry of amplitudes in N=4 super Yang-Mills theory in terms of eigenvalue relations for monodromy matrix operators. The Quantum Inverse Scattering Method provides us the appropriate tools to treat the extended symmetry and to recover as its consequences many known features like cyclic symmetry, BCFW recursion, Inverse Soft Limit construction, Grassmannian integral representation, R-invariants and on-shell diagram approach. | |
| Lance Dixon | The Hexagon Function Bootstrap
The hexagon function bootstrap constructs perturbative six-gluon amplitudes in planar N=4 super-Yang-Mills theory entirely from their analytic properties, without ever inspecting any multi-loop integrand. The amplitude is assumed to be a linear combination of hexagon functions --- a particular set of multiple polylogarithms --- with coefficients that are rational numbers, unknown a priori. Physical constraints from the near-collinear (OPE) and multi-Regge limits provide enough linear equations to determine all the coefficients. This talk will review progress in applying the bootstrap to the remainder function for the MHV helicity configuration through four loops. Ratios of successive loop orders are remarkably independent of the cross ratios. The NMHV amplitude has now also been determined through three loops. The NMHV amplitude allows the exploration of multi-particle factorization limits, which are inaccessible in the MHV case. It also provides new information about the multi-Regge limit. | |
| Claude Duhr | The gluon-fusion cross section at N3LO in the soft limit.
I discuss the recent computation of the Higgs-production cross section via gluon fusion at N3LO in QCD in the soft-virtual approximation in the limit of a large top quark mass. I review the different ingredients needed to perform the cross section computation, and I emphasise the importance of various techniques developed by the amplitudes community at various steps throughout the computation. | |
| Valentina Forini | Unitarity methods for scattering in two dimensions
I will discuss how the standard unitarity-cut method can be applied to several massive two-dimensional models - including the world-sheet superstring models relevant for the AdS/CFT correspondence - commenting on the features which ensure the cut-constructibility of their two-body S-matrices. | |
| Einan Gardi | Progress on long-distance singularities in gauge-theory scattering amplitudes
I will discuss the state-of-the-art knowledge of long-distance singularities to multi-leg gauge-theory scattering amplitudes and report on an on-going calculation of the three-loop soft anomalous dimension through the renormalization of correlators of semi-infinite Wilson lines. I will also discuss the non-Abelian exponentiation theorem that has been recently generalised to multiple Wilson lines and demonstrate its application in computing the soft anomalous dimension. Finally I will present recent results for multiple-gluon-exchange webs and discuss their analytic structure. | |
| Michael B. Green | Some features of closed string scattering amplitudes | |
| Johannes Henn | Mathematical methods for scattering amplitudes
In this talk I will review techniques for evaluating scattering amplitudes at loop level. I will give examples of recent applications in QCD and N=4 super Yang-Mills. | |
| Yu-tin Huang | Soft functions for general gauge and gravity theories | |
| Henrik Johansson | Color-Kinematics Duality for Matter Amplitudes
In this talk I consider Yang-Mills scattering amplitudes with fundamental matter. These can be used to construct gravity matter amplitudes, as well as pure gravity theories, via color-kinematics duality. | |
| Dmitri Kazakov | Amplitudes in D=6 N=(1,1) SYM theory | |
| Kasper Larsen | Cross-Order Integral Relations from Maximal Cuts
In this talk I will review the status of maximal unitarity at two loops. I will then discuss how the sharing of leading singularities between loop integrals exhibits consistency of maximal cuts with the KLN theorem, and furthermore how this sharing can be used to infer integral identities such as the ABDK/BDS identity | |
| Carlos Mafra | The superstring 3-loop amplitude | |
| Juan Maldacena | Causality constraints on graviton three point amplitudes | |
| Pierpaolo Mastrolia | Progress on Multi-Loop Scattering Amplitudes
I will discuss how generic properties of Scattering Amplitudes, like unitarity, factorization and loop momentum shift invariance can be combined with the idea of multivariate polynomial division of the integrands to achieve the decomposition of multi-loop amplitudes in terms of a minimal set of Master Integrals. I will also present a reducibility criterion for Feynman integrals, namely a test, based on purely algebraic operations, to verify whether a given integral is reducible, hence it is not Master Integral. Finally, I will show how Master Integrals can be computed through the Differential Equations method, and expressed in terms of iterated integrals of uniform transcendentality by means of Magnus and Dyson′s series. | |
| Ricardo Monteiro | Kinematic algebras in scattering amplitudes
We will describe the appearance of certain algebraic structures in the kinematic dependence of scattering amplitudes, both in gauge theory and in gravity. These structures mirror the colour dependence of the amplitude in the case of gauge theory, making the so-called colour/kinematics duality manifest. We will mainly focus on the kinematic algebras arising from the recently proposed scattering equations, which give a decomposition of the amplitude into simpler building blocks. We will also briefly discuss a different realisation of the kinematic algebra, inspired by the geometry of Lie groups. | |
| Brenda Penante | Simple form factors in N=4 super Yang-Mills
In this talk I will discuss how some modern techniques used in the study of scattering amplitudes (such as on-shell methods and symbols of transcendental functions) can be applied also in the context of form factors, which are partially off-shell quantities. In particular, I will consider MHV form factors of a supersymmetric extension of the half-BPS operators Tr(Phi^k) up to two loops. In analogy with amplitudes, these objects obey an exponentiation relation at two loops and thus one can define a finite (and surprisingly simple) remainder function. | |
| Radu Roiban | Scattering amplitudes in certain gauged supergravity theories
In this talk we explore an infinite class of gauged supergravity theories. We discuss the connection to their ungauged version, identify a double-copy structure and show how to compute their scattering amplitudes. | |
| Volker Schomerus | Polygon Amplitudes in the Multi-Regge Regime
I will review progress in computing the high energy limit of scattering amplitudes for planar N=4 super Yang-Mills theory both at weak and strong coupling. | |
| Vladimir Smirnov | Evaluating multiloop Feynman integrals by differential equations
A new strategy to solve differential equations for Feynman integrals has been recently suggested by Johannes Henn. After a set of master integrals is found using the integration-by-parts method, the crucial point of this strategy is to introduce a new basis where all master integrals are pure functions of uniform weight. This allows to cast the differential equations into a simple canonical form, which can straightforwardly be integrated order by order in epsilon in dimensional regularization. This method was successfully applied to planar three-loop four-point massless on-shell integrals, planar diagrams contributing to massive two-loop Bhabha scattering in QED, to so-called K4 diagram consisting of four external vertices which are connected with each other by six lines, to massless four-point integrals with two off-shell legs contributing to NNLO QCD corrections to the production of two off-shell vector bosons in hadron collisions. This method can be also applied to single-scale Feynman integrals. | |
| Emery Sokatchev | Energy-energy correlations in N=4 SYM
We study the event shapes in N=4 SYM describing the angular distribution of energy and charge in the final states created by the simplest half-BPS scalar operator. We compute this observable using the correlation functions of the N=4 stress-tensor supermultiplet. We find remarkably simple relations between various event shapes following from N=4 superconformal symmetry. Our results at leading order in the weak coupling expansion are in perfect agreement with the conventional amplitude technique. We present an analytic expression for the NLO energy-energy correlation. We extend the approach to strong coupling using the correlation function of half-BPS operators obtained from the AdS/CFT correspondence. | |
| Matthias Staudacher | N=4 Scattering Amplitudes and the Deformed Grassmannian | |
| Piotr Tourkine | The tropical limit and the UV behavior of N=4 supergravity | |
| Cristian Vergu | N=4 scattering amplitudes and the geometry of cluster coordinates
We will present some of the remarkable geometrical structures arising in N=4 scattering amplitudes. | |
| Ellis Yuan | Scattering Equations Recent Developments and Applications | |
| Gang Yang | Form factors in N=4 SYM and their applications
Form factors serve as an useful bridge between on-shell amplitudes and off-shell observables such as correlation functions. Sometimes they are also very interesting by themselves such as for computing cusp anomalous dimensions. As being shown by the studies in the past few years, the modern on-shell techniques can be largely used to compute form factors very efficiently. This opens a new avenue to the study as well as the application of amplitudes techniques. In this talk I will review part of these developments and some interesting applications along this direction. | |
| Yang Zhang | Integration-by-parts identities from the viewpoint of differential geometry
We present a new method to construct integration-by-parts (IBP) identities from the viewpoint of differential geometry. Vectors generating IBP identities are reformulated as differential forms, via Poincare duality. Using tools of differential geometry and commutative algebra, we efficiently obtain differential forms which generate on-shell IBP relations without doubled propagators. Various 4D two-loop examples are presented. |