Friday, 14 March 2008

Are these notions of strongly equivariant D-modules equivalent?

It seems that there are two notions of strongly equivaraint $D_X$- Modules and I would like to know if they are equivalent, or at least how they are related.
Let $rho: Gtimes X rightarrow X$ be an action of an algebraic group on a smooth variety over the complex numbers.
The first definition goes like this:



An equivariant $D_X$ Module is just a $D_X$ module $M$ together with an isomorphism
$$rho^* Mrightarrow pi^* M$$ of $D_{Gtimes X}$ -modules. That isomorphism has to satisfy some cocycle condition.



The other definition is a bit more cumbersome to write down. First it requires just an isomorphism of $O_{Gtimes X}$ modules, not necessarily of $D_{Gtimes X}$-modules $$rho^* Mrightarrow pi^* M$$ modules, which again satisfies the cocycle conditon.
In addition it requires the action map $$D_Xotimes M rightarrow M$$ to be equivariant.
Finally there is another condition to be satisfied:
Observe that we get two operations of the liealgera on $M$:



One operation, by directly differentiating the action of $G$ on $M$.



Another operation in the following way: First we differentiate the action of $G$ on $X$, and get a map
$$Lie(G)rightarrow Der_X$$
from the liealgebra into vectorfields on $X$. Because $M$ is a $D_X$ module we can compose this map with the action of vectorfields on $M$ and get our second operation.



We require these operations to coincide.



A more precise definition of the second kind is given here on pages 48-49:
http://www.math.harvard.edu/~gaitsgde/267y/catO.pdf



So the question is, are these two notions equivalent?



Edit: If anybody else needs these facts, I found a reference which gives a proof:
http://alpha.uhasselt.be/Research/Algebra/Publications/Geq.ps

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