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Hilbert-Speiser number fields and Stickelberger ideals

Humio Ichimura (2009)

Journal de Théorie des Nombres de Bordeaux

Let p be a prime number. We say that a number field F satisfies the condition ( H p n ) when any abelian extension N / F of exponent dividing p n has a normal integral basis with respect to the ring of p -integers. We also say that F satisfies ( H p ) when it satisfies ( H p n ) for all n 1 . It is known that the rationals satisfy ( H p ) for all prime numbers p . In this paper, we give a simple condition for a number field F to satisfy ( H p n ) in terms of the ideal class group of K = F ( ζ p n ) and a “Stickelberger ideal” associated to the Galois group...

Indices of subfields of cyclotomic ℤₚ-extensions and higher degree Fermat quotients

Yoko Inoue, Kaori Ota (2015)

Acta Arithmetica

We consider the indices of subfields of cyclotomic ℤₚ-extensions of number fields. For the nth layer Kₙ of the cyclotomic ℤₚ-extension of ℚ, we find that the prime factors of the index of Kₙ/ℚ are those primes less than the extension degree pⁿ which split completely in Kₙ. Namely, the prime factor q satisfies q p - 1 1 ( m o d p n + 1 ) , and this leads us to consider higher degree Fermat quotients. Indices of subfields of cyclotomic ℤₚ-extensions of a number field which is cyclic over ℚ with extension degree a prime different...

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