Classical, Motivic and Equivariant Stable Homotopy Groups of Spheres.

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Topology is a subject of mathematics that studies the shapes of spaces and interactions among them. A fundamental problem in topology is the classification problem of topological spaces and maps among them. Among all spaces, the spheres are of central importance, and we can classify them up to continuous deformation by a single number - the dimension. A one dimensional sphere, which we usually call a circle, is something that we can draw on a piece of paper, and can be described by the solutions of the familiar equation for a circle. A two dimensional sphere is something we can visualize in three dimensional space, such as the surface of a basketball, and can be described by the solutions of a similar equation. In topology, we also study higher dimensional spheres. Although these spaces cannot be visualized in three dimensions, they do exist in higher dimensions, and can also be studied. Somewhat surprisingly, maps between spheres are much harder to classify, even up to continuous deformations. This classification problem of maps between spheres is called the problem of computations of homotopy groups of spheres. This problem has been a major and active research problem since the 1950's. Much progress has been made on this problem, through all kinds of methods that have close connections to many subjects of mathematics. Recently, significant progress has been made using techniques from motivic and equivariant homotopy theory. The goal of this project is to further develop new techniques in motivic and equivariant homotopy theory, and to study this classical problem of computations of homotopy groups of spheres. Graduate students will be involved in this project.This project concentrates on computations of stable homotopy groups of spheres, in the classical, motivic and equivariant context. More specifically, the principal investigator and collaborators will continue using techniques in motivic homotopy theory over the complex numbers to push classical computations, towards the Kervaire invariant problem in dimension 126. The principal investigator and collaborators will extend the Chow t-structure technique defined over the complex numbers to other base fields, and study motivic stable homotopy groups of spheres over these base fields. Moreover, the PI will study with collaborators the New Doomsday Conjecture in Adams filtration 3, and use equivariant techniques to study homotopy groups of Hill-Hopkins-Ravenel type spectra.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.