Universal normal bases for the abelian closure of the field of rational numbers
Let denote the class number of -th layer of the cyclotomic -extension of . Weber proved that is odd and Horie proved that is not divisible by a prime number satisfying . In a previous paper, the authors showed that is not divisible by a prime number less than . In this paper, by investigating properties of a special unit more precisely, we show that is not divisible by a prime number less than . Our argument also leads to the conclusion that is not divisible by a prime number...