Moduli stack of formal group laws explained

In algebraic geometry, the moduli stack of formal group laws is a stack classifying formal group laws and isomorphisms between them. It is denoted by

l{M}FG

. It is a "geometric “object" that underlies the chromatic approach to the stable homotopy theory, a branch of algebraic topology.

Currently, it is not known whether

l{M}FG

is a derived stack or not. Hence, it is typical to work with stratifications. Let
n
l{M}
FG
be given so that
n
l{M}
FG

(R)

consists of formal group laws over R of height exactly n. They form a stratification of the moduli stack

l{M}FG

.

\operatorname{Spec}\overline{Fp}\to

n
l{M}
FG
is faithfully flat. In fact,
n
l{M}
FG
is of the form

\operatorname{Spec}\overline{Fp}/\operatorname{Aut}(\overline{Fp},f)

where

\operatorname{Aut}(\overline{Fp},f)

is a profinite group called the Morava stabilizer group. The Lubin–Tate theory describes how the strata
n
l{M}
FG
fit together.

References

Further reading