Totally, set theory is deep dark magic and tbh set theorists kinda scare me. Like they'll gleefully introduce incredibly complicated objects with very little intuition about them
Sivecano
joined 2 years ago
You know the top left one. They teach that in schools.
I mean... Ideal theory of rings? (Smth like (5) ∪ (7))
Set theory is relatively lawful.
yeah, top-left is regular multiplication. Top-center actjally is the so-called alternating product (basically the correct way of defining the cross product).
Top-right is supposed to be the operation in a gtoup.
There's no explicit cartesian product here but the middle one is the tensor product. The tensor prodict of sets (in so far as that statement makes sense) is the cartesian product.
:)