  We give an action of a Lie subalgebra of the Witt algebra on foams. This
action is compatible with the $\mathfrak{gl}_N$-foam evaluation formula. In
particular, this endows states spaces associated with $\mathfrak{gl}_N$-webs
with an $\mathfrak{sl}_2$-action. When working in positive characteristic, this
can be used to define a $p$-DG structure on these state spaces.
