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Fields of characteristic $p$, i.e., fields for which there is a prime $p$ such that $px=0$ for each $x$. Do not use this tag for questions on characteristic polynomials of a matrix.

15 votes

Is $Sym^n (V^*) \cong Sym^n (V)^\ast$ naturally in positive characteristic?

The dual to symmetric powers of a projective module of finite rank over any commutative ring is most elegantly expressed in terms of divided powers (thereby also "explaining" why over a field of nonze …
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8 votes

One dimensional (phi,Gamma)-modules in char p

The correspondence requires the $(\phi,\Gamma)$-module to have the \'etale property for its underlying $\phi$-module, and this plays an essential role in the proof of the correspondence (see Fontaine' …
BCnrd's user avatar
  • 7,108
5 votes
Accepted

If the morphism of root data induced by an isogeny of a reductive group is a Frobenius, is t...

The answer is "yes", but not in a good way: the descent it arises from is the split form, so this does not encode an interesting $\mathbf{F}_ q$-structure. More precisely, $f$ arises from the $q$-Fr …
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  • 7,108