ELI5: Explain Like I'm 5

Topological K-theory

Topological K-theory is a way of studying shapes and spaces in mathematics. It's like a big puzzle where we try to understand how these shapes fit together and what their properties are.

Imagine you have two different puzzle pieces - a square and a triangle. You can see that they are different shapes, but how can you tell which one is "better" than the other? Topological K-theory gives us a way of comparing shapes like these and understanding their differences.

To understand how topological K-theory works, let's try an example. Imagine you have a rubber band and you can stretch it and shape it however you like. You could make a circle, a square or a triangle by adjusting the shape of the rubber band. These different shapes are called topological spaces.

Now, let's say you have two rubber bands - one is just a plain circle and the other is a circle with a knot tied in it. If you tried to stretch them and shape them, you would find that they are different and you cannot turn one into the other without cutting the rubber band.

Topological K-theory helps us understand these differences between shapes like these. It looks at how the rubber band can be stretched and moved without changing its fundamental shape. This helps us understand how different shapes are "connected" to each other.

Finally, imagine you have a whole bunch of rubber bands - or topological spaces - and you want to compare all of them. Topological K-theory gives us an organized way to do this by assigning each space a number or value that helps us understand how it is related to the other spaces.

In summary, topological K-theory is a way of understanding and comparing shapes and spaces. It helps us understand how different shapes are related to each other and assign a numerical value to each shape to help us compare them.