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2 votes
1 answer
159 views

Field extensions and completions at possibly infinite places

In Serre's Corps Locaux, Chapter 2 §3, is presented a classical proof. We are in an "ABKL" setup, where $K/L$ is finite, $A$ is Dedekind, $B$ is the integral closure of $A$ and $B$ is $A$-...
Adrien Zabat's user avatar
0 votes
1 answer
147 views

Existence of linear disjointness between an algebraic number field and $p$-cyclotomic field over $ \mathbb{Q}$

Suppose $ K $ be an algebraic number field and $ n $ be an even integer. Is it possible to find atleast one $ p $ such that $ p\equiv 1( \text{mod}~ n)$ and $ \mathbb{Q}(\eta_p) $ is linearly disjoint ...
Sky's user avatar
  • 923
3 votes
1 answer
1k views

irreducibility of the polynomial $ x^4 +1 $

Let $K$ be a field. We consider the polynomial $f(x) = x^4 + 1$. It is known that $f(x)$ is irreducible over $\mathbb{Q}$ but reducible over any finite field. Thus $ f(x)$ is reducible over any field $...
Sky's user avatar
  • 923
6 votes
2 answers
329 views

Algebraic numbers which prescribed degree which does not belong to some fields

In my research it would be great if the following result is valid. In what follows, $\overline{\mathbb{Q}}$, $\overline{\mathbb{Q}}_n$ and $\overline{\mathbb{Q}}_{<n}$ denotes the set of algebraic ...
Jean's user avatar
  • 515
2 votes
0 answers
311 views

Degree $8$ cyclic extension over $\mathbb{Q}$

Actually I am interested in degree $ 8 $ cyclic extension over $ \mathbb{Q} $. Let $ L $ be such extension. At first I was thinking to take basis as normal basis, as we can determine the galois group ...
Sky's user avatar
  • 923
2 votes
0 answers
171 views

residue fields of smooth $\mathbf{Q}$-algebras

Let $A$ be a $\mathbf{Q}$-algebra. We say $A$ is "residually abelian", if there exists a maximal ideal $\mathfrak{m}$ of $A$ whose residue field $\kappa(\mathfrak{m})$ is a Kummer extension of an ...
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