The Stacks project

Add period

Thanks to Mingchen
https://stacks.math.columbia.edu/tag/07X1#comment-7736

Try to use L/K notation for field extensions

We could also try to consistenly use "field extension" and not just
"extension" and consistently use "ring extension", etc.

Better notation for deformation problems

Strong formal effectiveness => openness versality

Actually not hard to prove and you only need to check on first order
thickenings.

Bhargav's example from c31011d shows that strong formal effectiveness
does not always hold. But what about strong formal effectiveness
where the thickenings are always first order (between any two, not
just between consecutive indices)? This is the only thing needed for
the argument here, so it would be nice if it was true for algebraic
stacks in general.

A tiny typo (mostly testing the github approach).

\textit{Sch} ---> \Sch

Tags: Added new tags

First version of Artin's theorems

	This monster commit contains the first version of Artin's
	theorems on representability of stacks and spaces. It is still a
	bit rough.

Formal objects and effectivity

Finite dimensional tangent spaces

	The preceding 4 commits all lead up to this...