Cyclotomic field: Difference between revisions

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==References==
==References==
* {{cite book | author=A. Fröhlich | authorlink=Ali Fröhlich | coauthors=M.J. Taylor | title=Algebraic number theory | series=Cambridge studies in advanced mathematics | volume=27 | publisher=[[Cambridge University Press]] | year=1991 | isbn=0-521-36664-X }}
* {{cite book | author=A. Fröhlich | authorlink=Ali Fröhlich | coauthors=M.J. Taylor | title=Algebraic number theory | series=Cambridge studies in advanced mathematics | volume=27 | publisher=[[Cambridge University Press]] | year=1991 | isbn=0-521-36664-X }}
* {{cite book | author=Serge Lang | authorlink=Serge Lang | title=Cyclotomic Fields I and II | edition=Combined 2nd edition | publisher=Springer-Verlag | series=[[Graduate Texts in Mathematics]] | volume=121 | date=1990 | isbn=0-387-96671-4 }}
* {{cite book | author=Pierre Samuel | authorlink=Pierre Samuel | title=Algebraic number theory | publisher=Hermann/Kershaw | year=1972 }}
* {{cite book | author=I.N. Stewart | authorlink=Ian Stewart (mathematician) | coauthors=D.O. Tall | title=Algebraic number theory | publisher=Chapman and Hall | year=1979 | isbn=0-412-13840-9 }}
* {{cite book | author=I.N. Stewart | authorlink=Ian Stewart (mathematician) | coauthors=D.O. Tall | title=Algebraic number theory | publisher=Chapman and Hall | year=1979 | isbn=0-412-13840-9 }}
* {{cite book | author=Pierre Samuel | authorlink=Pierre Samuel | title=Algebraic number theory | publisher=Hermann/Kershaw | year=1972 }}
* {{cite book | author=Lawrence C. Washington | authorlink=Lawrence C. Washington | title=Introduction to Cyclotomic Fields | publisher=Springer-Verlag | series=[[Graduate Texts in Mathematics]] | volume=83 | date=1982 | isbn=0-387-90622-3 }}

Revision as of 17:23, 15 December 2008

In mathematics, a cyclotomic field is a field which is an extension generated by roots of unity. If ζ denotes an n-th root of unity, then the n-th cyclotomic field F is the field extension .

Ring of integers

As above, we take ζ to denote an n-th root of unity. The maximal order of F is

Unit group

Class group

Splitting of primes

A prime p ramifies iff p divides n. Otherwise, the splitting of p depends on the factorisation of the polynomial modulo p, which in turn depends on the highest common factor of p-1 and n.

Galois group

The minimal polynomial for ζ is the n-th cyclotomic polynomial , which is a factor of . Since the powers of ζ are the roots of the latter polynomial, F is a splitting field for and hence a Galois extension. The Galois group is isomorphic to the multiplicative group, via

References