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Questions about the branch of algebra that deals with groups.

29 votes
3 answers
4k views

Galois theory timeline

A recent question on the history of Galois theory wasn't the most satisfactory. But the historical issues do seem quite attractive. They relate to innovation, and to exposition. There is a perspective …
Charles Matthews's user avatar
17 votes

Is there a "crash-course" book on Abelian varieties (e.g., an introduction for physicists)?

Topics in Complex Function Theory, Abelian Functions and Modular Functions of Several Variables by C. L. Siegel is a standard reference using complex function theory. There are older works (e.g. H. F. …
Charles Matthews's user avatar
13 votes
Accepted

Ado's Theorem Proof

Your argument fails because the bracket can (sometimes) take pairs of elements into the centre. Therefore the direct sum as vector spaces isn't necessarily a direct sum of Lie algebras. For nilpotent …
Charles Matthews's user avatar
5 votes

Generating the symplectic group

By looking mod p for some primes you are actually testing a condition more relevant to determining whether the subgroup generated is Zariski-dense in the symplectic group. This is a kind of heuristic …
Charles Matthews's user avatar
3 votes

Feit-Thompson theorem: the Odd order paper

The Wikipedia article Odd order theorem is worth reading.
Charles Matthews's user avatar
3 votes

Groups acting on Riemann Surfaces

Q1: A typical Riemann surface has no holomorphic automorphisms, and this implies a negative answer to Q2. I don't see that Q3 can work: the p-subgroups surely don't uniquely determine the group in gen …
Charles Matthews's user avatar
3 votes

group scheme neither affine, nor an abelian variety

The type of Jacobian (generalised) discussed in Serre's book "Groupes algébriques et corps de classes" provides a large class of examples. They arise, in a sense, from the universality of the Albanese …
Charles Matthews's user avatar
2 votes

Center of p-groups

The center of a group cannot be of prime index, because a non-central element must fail to commute with something, which therefore cannot be one of its powers.
Charles Matthews's user avatar
2 votes

Is there a classification of possible linear actions?

A Möbius transformation (http://en.wikipedia.org/wiki/Möbius_transformation) is usually considered as acting on the projective line, which is associated to a two-dimensional vector space. Roughly spea …
Charles Matthews's user avatar
1 vote

group action and orbit space

I don't really see why there should be general results. We can take W to be a vector space over a finite field, and then you are asking about equivalence of linear representations of G on W. The data …
Charles Matthews's user avatar
1 vote

A question regarding polynomials whose roots satisfy certain algebraic relation

Such questions formed a substantial part of the classical "theory of equations", before Galois theory was formulated. For example, there is a book by Burnside on theory of equations, that is easy to f …
Charles Matthews's user avatar
1 vote

Parametrization of O(3)

If there were a really simple way we wouldn't need the concept of "gimbal lock" (http://en.wikipedia.org/wiki/Gimbal_lock). In other words the manifold in question is compact but isn't the 3-torus, an …
Charles Matthews's user avatar
1 vote

groups and asymmetry

"Broken symmetry", rather than complete and utter asymmetry, is an important concept for physicists. See http://en.wikipedia.org/wiki/Symmetry_breaking. I suppose this all goes back to Buridan's ass ( …
Charles Matthews's user avatar
1 vote

(A very limited instance of) Lagrange's Theorem's converse and A_5

See http://en.wikipedia.org/wiki/N-group_%28finite_group_theory%29 where it talks about minimal simple groups. You'd need to check in particular that the example of 2x2 projective special linear group …
Charles Matthews's user avatar