Plücker varieties

Grassmannians form a family of varieties that is stable under
applying linear maps and taking duals. We discuss families
like this in more generality, and give the results we found.

Most importantly, if a family is bounded in a certain way,
we show that it is determined by only finitely many equations
up to symmetry. In particular, this can give us a way to test
membership of a given family in polynomial time.