PlanetMath (more info)
 Math for the people, by the people.
Encyclopedia | Requests | Forums | Docs | Wiki | Random | RSS  
Login
create new user
name:
pass:
forget your password?
Main Menu
Owner confidence rating: High Entry average rating: No information on entry rating
Stickelberger's theorem (Theorem)
Theorem 1 (Stickelberger)   Let $ L=\mathbb{Q}(\zeta_m)$ be a cyclotomic field extension of $ \mathbb{Q}$ with Galois group $ G=\{\sigma_a\}_{a\in(\mathbb{Z}/m\mathbb{Z})^\times}$, and consider the group ring $ \mathbb{Q}[G]$. Define the Stickelberger element $ \theta\in\mathbb{Q}[G]$ by
$\displaystyle \theta=\frac{1}{m}\sum_{1\leq a\leq m, (a,m)=1}a\sigma_a^{-1},$    

and take $ \beta\in\mathbb{Z}[G]$ such that $ \beta\theta\in\mathbb{Z}[G]$ as well. Then $ \beta\theta$ is an annihilator for the ideal class group of $ \mathbb{Q}(\zeta_m)$.

Note that $ \theta$ itself need not be an annihilator, just that any multiple of it in $ \mathbb{Z}[G]$ is.

This result allows for the most basic connections between the (otherwise hard to determine) structure of a cyclotomic ideal class group and its collection of annihilators. For an application of Stickelberger's theorem, see Herbrand's theorem.



"Stickelberger's theorem" is owned by mathcam.
(view preamble)

View style:

Also defines:  Stickelberger element
Log in to rate this entry.
(view current ratings)

Cross-references: Herbrand's theorem, multiple, ideal class group, annihilator, group ring, Galois group, extension, cyclotomic field
There are 2 references to this entry.

This is version 3 of Stickelberger's theorem, born on 2004-02-27, modified 2004-03-02.
Object id is 5642, canonical name is StickelbergersTheorem.
Accessed 2575 times total.

Classification:
AMS MSC11R29 (Number theory :: Algebraic number theory: global fields :: Class numbers, class groups, discriminants)

Pending Errata and Addenda
None.
[ View all 2 ]
Discussion
Style: Expand: Order:
forum policy

No messages.

Interact
post | correct | update request | prove | add result | add corollary | add example | add (any)