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Aug 18, 2017 at 14:05 comment added cheyne I edited my question. Is $\Omega$ an Azumaya Algebra?
Aug 15, 2017 at 18:31 comment added Daniel Litt If one wants some kind of connection, presumably one should look at Cech $H^1$ of the complex $PGL(E)\to \Omega^1(\text{End}(E))/\Omega^1$ where the arrow is given by dlog; for flat connections, one probably wants $PGL(E)\to\Omega^1(\text{End}(E))/\Omega^1\to \Omega^2(\text{End}(E))/\Omega^2$...
Aug 15, 2017 at 18:14 comment added Daniel Litt Does $\text{End}(E)^*$ mean units in $\text{End}(E)$? If so I think this still isn't right; instead one wants $1$-cocycles for $PGL(E)$ (since the center of $\text{End}(E)$ acts trivially on $\text{End}(E)$ by conjugation). Then the associated Brauer class comes from the exact sequence $0\to O^*\to GL(E)\to PGL(E)\to 0$.
Aug 15, 2017 at 18:10 history edited Ben Webster CC BY-SA 3.0
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Aug 15, 2017 at 17:06 comment added cheyne Interestingly, this is all sounding quite gerbe-related now that you're saying things are classified by closed 2-forms. But that excitement aside, @BenWebster , we can't say something like "$\Omega$ is an Azumaya algebra"?
Aug 15, 2017 at 17:02 comment added cheyne I'm also very interested (eventually) in the curved case but for now I'll settle for a flat discussion.
Aug 15, 2017 at 16:13 comment added David E Speyer I'm hoping you'll clear this up, because its something I've never gotten straight.
Aug 15, 2017 at 16:04 comment added mme @BenWebster Is there some well-behaved deformation theory for curved algebras with fixed curvature?
Aug 15, 2017 at 15:47 history edited Ben Webster CC BY-SA 3.0
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Aug 15, 2017 at 15:47 comment added Ben Webster Hmm, you're right of course. Though presumably there is some way of fixing this even for bundles without projectively flat connections.
Aug 15, 2017 at 14:10 comment added David E Speyer The sheaf has to be equipped with a connection, and the choice of connection matters.
Aug 15, 2017 at 13:53 history answered Ben Webster CC BY-SA 3.0