ELI5: Explain Like I'm 5

Arithmetic topology

Arithmetic topology is a type of math where we use numbers to think about shapes and spaces. Imagine you have a rubber band and you can stretch it and twist it in different ways. Arithmetic topology helps us understand how those different shapes and twists affect the rubber band.

Let's pretend we have a piece of paper with some shapes on it, and we want to know how many ways we can cut it up and rearrange the pieces without changing the overall shape. This is called a "topological invariant" because it stays the same no matter how we manipulate the paper. We can use arithmetic topology to figure out what the invariant is for different shapes.

One important concept in arithmetic topology is the idea of a "cycle". Imagine you draw a loop on a piece of paper, like a circle. If you trace along the circle without lifting your pencil, you end up back where you started. This is called a cycle. In arithmetic topology, we can use numbers to represent cycles and study how they behave when we twist and stretch them.

Another key idea in arithmetic topology is the "fundamental group". This is like the rulebook for how cycles behave in a given shape. It tells us everything we need to know about the cycles in that shape and how they interact with each other.

In summary, arithmetic topology is a way to use numbers to understand shapes and spaces, specifically focusing on cycles and the fundamental group.