Amit Sever

Y-system for scattering amplitudes

We compute super Yang–Mills planar amplitudes at strong coupling by considering minimal surfaces in AdS5 space. The surfaces end on a null polygonal contour at the boundary of AdS. We show how to compute the area of the surfaces as a function of the conformal cross ratios characterizing the polygon at the boundary. We reduce the problem to a simple set of functional equations for the cross ratios as functions of the spectral parameter. These equations have the form of thermodynamic Bethe ansatz (TBA) equations. The area is the free energy of the TBA system. We consider any number of gluons and in any kinematic configuration.

An operator product expansion for polygonal null Wilson loops

We consider polygonal Wilson loops with null edges in conformal gauge theories. We derive an OPE-like expansion when several successive lines of the polygon are becoming aligned. The limit corresponds to a collinear, or multicollinear, limit and we explain the systematics of all the subleading corrections, going beyond the leading terms that were previously considered. These subleading corrections are governed by excitations of high spin operators, or excitations of a flux tube that goes between two Wilson lines. The discussion is valid for any conformal gauge theory, for any coupling and in any dimension.For

Tailoring three-point functions and integrability

\mathcal{N} = 4

The quark anti-quark potential and the cusp anomalous dimension from a TBA equation

super Yang Mills we check this expansion at strong coupling and at two loops at weak coupling. We also make predictions for the remainder function at higher loops.In the process, we also derived a new version for the TBA integral equations that determine the strong coupling answer and present the area as the associated Yang-Yang functional.

An exact formula for the radiation of a moving quark in \mathcal{N} = 4 super Yang Mills

We use integrability techniques to compute structure constants in

Spacetime and flux tube S-matrices at finite coupling for N=4 supersymmetric Yang-Mills theory.

\mathcal{N} = 4

Pulling the straps of polygons

SYM to leading order at weak coupling and to leading order in the planar expansion. Three closed spin chains, which represent the single trace gauge-invariant operators in

Space-time S-matrix and flux tube S-matrix II. Extracting and matching data

\mathcal{N} = 4

Space-time S-matrix and Flux-tube S-matrix at Finite Coupling

SYM, are cut into six open chains which are then sewed back together into some nice pants, the three-point function. The algebraic and coordinate Bethe ansatz tools necessary for this task are reviewed. Our results hold for scalar single trace operators of arbitrary size. Finally, we discuss the classical limit of our results, anticipating some predictions for quasi-classical string correlators in terms of algebraic curves.

Tailoring three-point functions and integrability II. Weak/strong coupling match

A bstractWe derive a set of integral equations of the TBA type for the generalized cusp anomalous dimension, or the quark antiquark potential on the three sphere, as a function of the angles. We do this by considering a family of local operators on a Wilson loop with charge L. In the large L limit the problem can be solved in terms of a certain boundary reflection matrix. We determine this reflection matrix by using the symmetries and the boundary crossing equation. The cusp is introduced through a relative rotation between the two boundaries. Then the TBA trick of exchanging space and time leads to an exact equation for all values of L. The L = 0 case corresponds to the cusped Wilson loop with no operators inserted. We then derive a slightly simplified integral equation which describes the small angle limit. We solve this equation up to three loops in perturbation theory and match the results that were obtained with more direct approaches.