ELI5: Explain Like I'm 5

Harish-Chandra homomorphism

Imagine you have two friends who speak different languages and you want to play a game together. Unfortunately, you don't know their languages and they don't know yours!

But you're smart, and you think of a plan: you'll learn some key phrases in both languages, and then use those to translate what each of them is saying.

This is kind of like what the Harish-Chandra homomorphism does! It helps translate between two different kinds of math objects called Lie groups and Lie algebras. These things are like languages that mathematicians use to talk about certain kinds of symmetries and transformations.

The Harish-Chandra homomorphism takes information about symmetries (called representations) of a Lie group and turns it into information about a Lie algebra (which is sort of like the "grammar" of the symmetries). It's like taking what each friend is saying and translating it into a common language you all can understand.

This is really helpful for mathematicians because sometimes it's easier to work with Lie algebras than Lie groups, and sometimes it's easier the other way around. So the Harish-Chandra homomorphism helps us switch back and forth as needed, kind of like a translator helping you switch between Spanish and French in your game.