Weber's Theorem
Weber's theorem may refer to: *Kronecker–Weber theorem In algebraic number theory, it can be shown that every cyclotomic field is an abelian extension of the rational number field Q, having Galois group of the form (\mathbb Z/n\mathbb Z)^\times. The Kronecker–Weber theorem provides a partial conve ... * Weber's theorem (Algebraic curves) {{disambiguation ...
[...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]  

Kronecker–Weber Theorem
In algebraic number theory, it can be shown that every cyclotomic field is an abelian extension of the rational number field Q, having Galois group of the form (\mathbb Z/n\mathbb Z)^\times. The Kronecker–Weber theorem provides a partial converse: every finite abelian extension of Q is contained within some cyclotomic field. In other words, every algebraic integer whose Galois group is abelian can be expressed as a sum of roots of unity with rational coefficients. For example, :\sqrt = e^ - e^ - e^ + e^, \sqrt = e^ - e^, and \sqrt = e^ - e^. The theorem is named after Leopold Kronecker and Heinrich Martin Weber. Field-theoretic formulation The Kronecker–Weber theorem can be stated in terms of fields and field extensions. Precisely, the Kronecker–Weber theorem states: every finite abelian extension of the rational numbers Q is a subfield of a cyclotomic field. That is, whenever an algebraic number field has a Galois group over Q that is an abelian group, the field is a subfie ...
[...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]