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Contrary to simple transcendental extensions of $\mathbb{Q}$, which are necessarily isomorphic to a field of rational functions over $\mathbb{Q}$, simple algebraic extensions are very varied - which explains why we devote so much attention to them during Galois theory.

One particular "family" of such extensions are the cyclotomic extensions (i. e., extensions of the form $\mathbb{Q}(\theta)$, where $\theta^n = 1$ for some $n$). These are quite frequent and I've seen multiple books devoting at least a section specific to them (especially considering prime values of $n$).

That said, this is the only well-known "family" of algebraic numbers I know of (at least, that I can recall). Of course, I could simply give roots of equations of the form, say, $x^n - x - 1$ a name and study their properties, but why focus on this group specifically? This leads me to ponder:

Are there any other groups of algebraic numbers - perhaps roots of equations of a special form - that receive distinguished attention, besides the roots of unity? If so, which ones and where do they show up?

Thanks in advance!

Gauss
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    Constructible numbers, dear Gauss ;-) – Anne Bauval Jun 01 '23 at 16:32
  • @AnneBauval Fair enough! Although they are not related in the sense of having a similar minimal polynomial, as far as I recall – Gauss Jun 01 '23 at 17:56
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    There are some nice algebraic numbers coming from hypergeomtreic functions, see here. – Dietrich Burde Jun 01 '23 at 18:28
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    Over fields with characteristic $p$ prime, the Artin-Schreier equations $x^p-x-a=0$ are interesting. – paul garrett Jun 01 '23 at 18:40
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    It's much fancier, but the Kronecker "youth dream" of explicit generation of abelian-Galois extensions of quadratic complex fields $\mathbb Q(\sqrt{-D})$ (with $D>0$ by values of elliptic functions, or of elliptic modular functions, is a huge business in itself. – paul garrett Jun 01 '23 at 18:41
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    See also https://en.wikipedia.org/wiki/Kummer_theory – lhf Jun 01 '23 at 23:15
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    You also have Salem numbers. A survey of their propertie, including their Galois groups, may be found in https://www.maths.ed.ac.uk/~chris/papers/Salem_survey270814.pdf – GreginGre Jun 02 '23 at 17:36

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