On the Iwasawa λ-invariant of the cyclotomic ℤ2-extension of ℚ(pq) and the 2-part of the class number of ℚ(pq,2+2).

In this paper, we study the Iwasawa λ -invariant of the cyclotomic ℤ 2 -extension of ℚ (p q) , where p , q are distinct odd prime numbers satisfying certain arithmetic conditions. Moreover, we obtain an upper bound of the 2 -part of the class number of certain quartic number fields by calculating the Sinnott index explicitly. [ABSTRACT FROM AUTHOR]