ELI5: Explain Like I'm 5

Equivariant stable homotopy theory

Well, deep breath! Equivariant stable homotopy theory is like playing with toys and figuring out how they move and interact with each other, but with a really big toy box and lots of rules.

Let's start with the idea of a "homotopy." This is like when you have a line of toys, but you move one of the toys around slowly until it becomes a different toy without changing the overall line. It's called a homotopy because it's like two things are "homemade" from each other, get it?

Now, imagine each of these toys has a sticker on it, like a flag, that tells us which "group" it's in. This group is like a special team for the toy, and it can only hang out and play with other toys in the same team.

So, in equivariant stable homotopy theory, we're looking at what happens when we try to homotope, or change, the toys around while keeping these groups in mind. It's like playing with each group's own particular toy box - each group might have different kinds of toys or different ways they want to move around.

The "stable" part means we're looking at ways to make toys extra-strong and durable by attaching them to other toys in certain ways. It's like when you have a favorite toy that you always make sure is well-connected to other toys so it doesn't fall apart.

Now comes the tricky part - "equivariant." This means we're looking at the ways that the groups and the toys inside of them interact with each other. It's like how your team might have a special toy that they all play with together, and they have to figure out how to use it in a game. Or, how sometimes when two different toys are combined, they become even cooler than they were on their own!

So, in sum: equivariant stable homotopy theory is like playing with a big toy box that comes with lots of different groups of toys, and trying to make the toys extra-strong and connected while also figuring out how each group's toys want to work and play together. It's like a big puzzle that mathematicians work on by using special rules and techniques. But with toys! Cool, right?
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