On the index (R∶U) and the genus number of an abelian number field

1982 ◽  
Vol 39 (6) ◽  
pp. 546-550
Author(s):  
Makoto Ishida
Keyword(s):  
Number Field ◽  
Abelian Number Field ◽  
Genus Number

scholarly journals A congruence for the index of a unit of a real abelian number field

1985 ◽  
Vol 46 (1) ◽  
pp. 57-72
Author(s):  
Kenneth Williams ◽  
Kenneth Hardy
Keyword(s):  
Number Field ◽  
Abelian Number Field ◽  
Real Abelian Number Field

Prime splitting in abelian number fields and linear combinations of Dirichlet characters

2014 ◽  
Vol 10 (04) ◽  
pp. 885-903 ◽  
Author(s):  
Paul Pollack
Keyword(s):  
Number Field ◽  
Nonzero Element ◽  
Number Fields ◽  
Upper Bounds ◽  
Prime Ideals ◽  
Linear Combinations ◽  
Dirichlet Characters ◽  
Abelian Number Field ◽  
Splitting Type ◽  
A Finite Group

Let 𝕏 be a finite group of primitive Dirichlet characters. Let ξ = ∑χ∈𝕏 aχ χ be a nonzero element of the group ring ℤ[𝕏]. We investigate the smallest prime q that is coprime to the conductor of each χ ∈ 𝕏 and that satisfies ∑χ∈𝕏 aχ χ(q) ≠ 0. Our main result is a nontrivial upper bound on q valid for certain special forms ξ. From this, we deduce upper bounds on the smallest unramified prime with a given splitting type in an abelian number field. For example, let K/ℚ be an abelian number field of degree n and conductor f. Let g be a proper divisor of n. If there is any unramified rational prime q that splits into g distinct prime ideals in ØK, then the least such q satisfies [Formula: see text].

scholarly journals On unramified cyclic extensions of degree l of algebraic number fields of degree l

1987 ◽  
Vol 107 ◽  
pp. 135-146 ◽  
Author(s):  
Yoshitaka Odai
Keyword(s):  
Number Field ◽  
Algebraic Number ◽  
Preceding Paper ◽  
Algebraic Number Field ◽  
Number Fields ◽  
Maximal Extension ◽  
Algebraic Number Fields ◽  
Cubic Field ◽  
Genus Field ◽  
Abelian Number Field

Let I be an odd prime number and let K be an algebraic number field of degree I. Let M denote the genus field of K, i.e., the maximal extension of K which is a composite of an absolute abelian number field with K and is unramified at all the finite primes of K. In [4] Ishida has explicitly constructed M. Therefore it is of some interest to investigate unramified cyclic extensions of K of degree l, which are not contained in M. In the preceding paper [6] we have obtained some results about this problem in the case that K is a pure cubic field. The purpose of this paper is to extend those results.

On the class number of the lpth cyclotomic number field

1991 ◽  
Vol 109 (2) ◽  
pp. 263-276
Author(s):  
Norikata Nakagoshi
Keyword(s):  
Number Field ◽  
Class Number ◽  
Prime Factor ◽  
Analytic Formula ◽  
Cyclotomic Number ◽  
Class Number Formula ◽  
Prime Factors ◽  
Number Formula ◽  
Genus Number ◽  
Analytic Class

The first factor of the class number of a cyclotomic number field can be obtainable by the analytic class number formula and there are some tables which show the decompositions of the first factors into primes. But, using just the analytic formula, we cannot tell what kinds of primes will appear as the factors of the class number of a given cyclotomic number field, except for those of the genus number, or the irregular primes. It is significant to find in advance the prime factors, particularly those prime to the degree of the field. For instance, in the table of the first factors we can pick out some pairs (l, p) of two odd primes l and p such that the class number of each lpth cyclotomic number field is divisible by l even if p 1 (mod l). If p ≡ (mod l) for l ≥ 5 or p ≡ 1 (mod 32) for l = 3, then it is easy from the outset to achieve our intention of finding the factor l using the genus number formula. Otherwise it seems to be difficult. We wish to make it clear algebraically why the class number has the prime factor l.

scholarly journals The Schur group of an abelian number field

2009 ◽  
Vol 213 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Allen Herman ◽  
Gabriela Olteanu ◽  
Ángel del Río
Keyword(s):  
Number Field ◽  
Abelian Number Field

THE DISCRIMINANT OF ABELIAN NUMBER FIELDS

2006 ◽  
Vol 05 (01) ◽  
pp. 35-41 ◽  
Author(s):  
J. CARMELO INTERLANDO ◽  
JOSÉ OTHON DANTAS LOPES ◽  
TRAJANO PIRES DA NÓBREGA NETO
Keyword(s):  
Number Field ◽  
Number Fields ◽  
Abelian Number Field

A formula for computing the discriminant of any Abelian number field K is given. It is presented as a function of the conductor m of K and of the degrees of the fields K ∩ ℚ(ζpα) over ℚ, where p runs through the set of primes that divide m, and pα is the greatest power of p that divides m.

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