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9 votes
0 answers
261 views

Who was the first to prove that the automorphism group of a finite field is cyclic and is generated by the Frobenius automorphism?

$\DeclareMathOperator\Aut{Aut}$It is well-known that the automorphism group $\Aut(F)$ of a finite field $F$ of characteristic $p$ is cyclic of order $n$ where $|F|=p^n$. Moreover, the cyclic group $\...
2 votes
0 answers
124 views

Can K$_3$ of finite fields be related to Teichmüller cocycles?

This is sort of a blind shot, but... For a ring $R$, its third algebraic K-group is given by $\operatorname K_3(R)=H_3(\operatorname{St}(R))$. To simplify matters, let $R$ be a finite field $\mathbb ...
8 votes
1 answer
355 views

The distribution of certain Galois groups

Let $f(x)$ be a polynomial of degree $d$ with integer coefficients. Let $G_p^+$ be the Galois group of the polynomial $f(x)-y$ over $\overline{\mathbb{F}}_p(y)$ and $G_p$ be the Galois group of the ...
11 votes
3 answers
1k views

Cubic polynomials over finite fields whose roots are quadratic residues or non-residues

For a cubic polynomial $f(x)=x^3+x^2+\frac{1}{4}x+c$ over $\mathbb{F}_q$, where $q$ is a odd prime power, I find that for a lot of $q$, there does not exist $c\in\mathbb{F}_q$ such that $f$ has three ...
17 votes
0 answers
750 views

Elements of finite fields with many powers of trace zero

Let $p$ be an odd prime number, $n>1$ be an integer, and $\mathrm{tr}$ be the trace map of the field extension $\mathrm{GF}(p^{2n})/\mathrm{GF}(p)$. For which pair $(p,n)$ does there exists $x\in\...
3 votes
0 answers
285 views

What is known about the prime-to-$p$ etale fundamental group of $\mathbb{P}^1_{\mathbb{F}_p}$ minus $\mathbb{F}_p$-rational points?

Is it known to be (the prime-to-$p$ part of the profinite completion of) a finitely presentable group? Is such a presentation known? Is there a guess for what it is? What is known about it?
1 vote
1 answer
323 views

Maximal separable extension of $\mathbb F_q((t))$

Let $K=\mathbb F_q((t))$. I want to prove that $K^{sep}$ is composite of $K^{sep}(p)$ and $K^{sep}(not \ p)$, where $K^{sep}(p)$ is maximal Galois extension of $K$ of exponent $p$, $K^{sep}(not \ p)$ ...