In this talk will discuss a method to define Fenchel-Nielsen coordinates for representations of surface groups to SL(3,C). This both generalises and unifies the previous generalisations for PSL(2,C) by Kourouniotis and Tan, for SL(3,R) by Goldman and Zhang and for SU(2,1) by Parker and Platis.
For a punctured surface S and a split reductive algebraic group G such as SL_n or PGL_n, Fock and Goncharov (and Shen) consider two types of moduli spaces parametrizing G-local systems on S together with certain data at punctures. These moduli spaces yield versions of higher Teichmüller spaces, and are equipped with special coordinate charts, making them birational to cluster varieties. Fock and Goncharov’s duality conjectures predict the existence of a canonical basis of the algebra of regular functions on one of these spaces, enumerated by the tropical integer points of the other space. I will give an introductory overview of this topic, briefly explain recent developments involving quantum topology and mirror symmetry of log Calabi-Yau varieties, and present some open problems if time allows.
Positivity properties of scattering amplitudes are typically related to unitarity and causality. However, in some cases positivity properties can also arise from deeper underlying structures. In these lectures, we will discuss infinitely many positivity constraints that certain amplitudes and their derivatives obey called completely monotonicity in the mathematics literature.
In the first lecture, we will discuss completely monotone functions and some of their properties. We shall then show why some objects such scalar Feynman integrals admit this property via integral representations. In the second lecture, we will discuss the connection between complete monotonicity and positive geometries.
We discuss the newly introduced hidden zeros in a class of scattering amplitudes. We relate their existence to color-kinematics duality and the double copy. Further we also discuss splitting of the scattering amplitude near these zeros and show how such behaviour can be seen as a result of a residue theorem after a complex shift. Similar shifts allow us to calculate amplitudes of related theories as well.
Positivity properties of scattering amplitudes are typically related to unitarity and causality. However, in some cases positivity properties can also arise from deeper underlying structures. In these lectures, we will discuss infinitely many positivity constraints that certain amplitudes and their derivatives obey called completely monotonicity in the mathematics literature.
In the first lecture, we will discuss completely monotone functions and some of their properties. We shall then show why some objects such scalar Feynman integrals admit this property via integral representations. In the second lecture, we will discuss the connection between complete monotonicity and positive geometries.
I will give a brief review of some recent progress regarding mathematical aspects of three closely-related quantities in N=4 SYM theory: half-BPS correlators, the square of amplitudes and energy correlators.
