Timeline for a question of Galois cohomology
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| May 4, 2013 at 21:06 | comment | added | Ray Hoobler | Alternatively this cohomology group classifies principal homogeneous spaces for $PGl_2$ and these correspond precisely to rank 4 Azumaya algebras $A$ by descent theory. But you can lift idempotent elements in $\overline A$ over the residue field $k$ to idempotent elements in $A$ over $R$. Consequently any such algebra has non identity idempotents in it and so must be a 2×2 ring of matrices over $R$. The characteristic of $k$ or $K$ doesn't matter. | |
| May 3, 2013 at 3:35 | vote | accept | Miyako Nara | ||
| May 3, 2013 at 2:59 | history | edited | Kestutis Cesnavicius | CC BY-SA 3.0 |
added 106 characters in body
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| May 3, 2013 at 2:51 | history | answered | Kestutis Cesnavicius | CC BY-SA 3.0 |