ELI5: Explain Like I'm 5

Atiyah–Bott fixed-point theorem

Imagine you have a bunch of dots on a paper and you want to draw a line connecting them. You start at one dot and draw a line to the next dot, and so on, until you finish connecting all the dots. But what if you want to know how many times you have to lift your pen off the paper to make the lines?

This is where the Atiyah-Bott fixed-point theorem comes in. It helps you count the number of times you lift your pen when you’re drawing lines between dots. But instead of dots, we are talking about some mathematical objects called “vector bundles” on a surface, and instead of lines, we are talking about “paths” connecting these vector bundles.

The theorem says that if we have a certain type of vector bundle on a two-dimensional surface, and we draw paths between different points on this surface (in technical terms, we say these are closed loops), then the number of times we lift our pen is related to some special numbers that are associated with the vector bundle. These special numbers are called “Chern numbers.”

Chern numbers help us understand how vector bundles behave on a surface. They tell us things like whether a bundle can be twisted or turned inside-out or not. And the Atiyah-Bott fixed-point theorem gives us a way to compute these numbers by counting the number of times we lift our pen when we draw paths on the surface between different points.

In other words, the Atiyah-Bott fixed-point theorem is a special tool mathematicians use to understand how vector bundles work on surfaces. It helps us count the number of times we need to lift our pen when we connect different points on the surface, which gives us valuable information about the vector bundle.