ELI5: Explain Like I'm 5

Buchsbaum–Eisenbud acyclicity criterion

Okay kiddo, so you know how sometimes we have a bunch of things that are connected, like friends holding hands, and we say they make a circle or a chain?

Well, sometimes these things are connected in a really special way called a "complex." This means they are all tangled up together in a certain way, sort of like a complicated net. We call this a "simplicial complex."

Now, sometimes we want to know if this simplicial complex has a certain property called "acyclicity." This just means that there are no loops in the complex - no matter how you trace a path through the things in the complex, you can't end up where you started without going through the same thing twice.

But how can we tell if a simplicial complex is acyclic? That's where the Buchsbaum-Eisenbud Acyclicity Criterion comes in.

Basically, this criterion tells us that if we take away one thing from the complex - like one friend letting go of another's hand - and the resulting complex is still connected in a special way, then the original complex must be acyclic.

It's sort of like if we had a necklace with a bunch of beads on it. If we take away one bead and the necklace is still in one piece, with no extra loops or anything, then the original necklace must have no loops either.

So that's the gist of it, kiddo - the Buchsbaum-Eisenbud Acyclicity Criterion helps us figure out if a complicated net of connections has any loops in it.