Department of Mathematics, Faculty of Science, Okayama UniversityActa Medica Okayama0030-15664812006Stickelberger Ideals and Normal Bases of Rings of p-integersENHumioIchimuraNo potential conflict of interest relevant to this article was reported.Department of Mathematics, Faculty of Science, Okayama UniversityActa Medica Okayama0030-15665412012HILBERT-SPEISER NUMBER FIELDS AND STICKELBERGER IDEALS; THE CASE p = 23348ENHumioIchimuraWe say that a number field F satisfies the condition (H′<sub>2<sup>m</sup></sub>) when any abelian extension of exponent dividing 2<sup>m </sup> has a normal basis with respect to rings of 2-integers. We say that it satisfies (H′
<sub>2<sup>∞</sup></sub>) when it satisfies (H′
<sub>2<sup>m</sup></sub>) for all m. We give a condition for F to satisfy (H'<sub>2<sup>m</sup></sub>), and show that the imaginary quadratic fields F = Q(√−1) and Q(√−2) satisfy the very strong condition (H′
<sub>2<sup>∞</sup></sub>) if the conjecture that h<sup>+</sup><sub>2<sup>m</sup></sub> = 1 for all m is valid. Here, h<sup>+</sup><sub>2<sup>m</sup></sub>) is the class number of the maximal real abelian field of conductor 2<sup>m</sup>.No potential conflict of interest relevant to this article was reported.Department of Mathematics, Faculty of Science, Okayama UniversityActa Medica Okayama0030-15665812016On a duality of Gras between totally positive and primary cyclotomic units125132ENHumioIchimuraLet K be a real abelian field of odd degree over Q, and C the group of cyclotomic units of K. We denote by C+ and C0 the totally positive and primary elements of C, respectively. G. Gras found a duality between the Galois modules C+/C2 and C0/C2 by some ingenious calculation on cyclotomic units. We give an alternative proof using a consequence (=“Gras conjecture”) of the Iwasawa main conjecture and the standard reflection argument. We also give some related topics.No potential conflict of interest relevant to this article was reported.