The Stacks project

LaTeX

Introduced a macro

\def\Ker{\text{Ker}}

and replace all occurrences of \text{Ker} with \Ker

\text{Mod}(R) ---> \text{Mod}_R and similar

Excise finite type conditions

We need to have the functors T_x and Inf_x for all modules not just
for finite type ones. This actually simplifies the discussion a
tiny bit as we don't have to carry along the finite type conditions
everywhere.

Thanks to David Rydh for pointing this out (see
commit 2ccbbe3087e4dc2b1df2193c81ede7486931424c for more
information).

Tags: Added new tags

Some material about obstruction theories

	This includes the notion of a naive obstruction theory and a
	proof that such a thing is good enough to give openness of
	versality. This was introduced on the blog

	http://math.columbia.edu/~dejong/wordpress/?p=2472

	It is just working out what you would get if you actually had an
	algebraic stack. It seems likely that Artin was motivated in
	formulating his axioms by the idea that such a thing should
	exist.

	Hopefully we can use this to prove openness of versality for
	some nice cases such as families of proper flat algebraic
	spaces... We'll see.