On the class numbers of algebraic number fields
O. M. Fomenko St. Petersburg Department of V. A. Steklov Institute of Mathematics of the Russian Academy of Sciences, St. Petersburg, Russia
Abstract:
Let
$K$ be a number field of degree
$n$ over
$\mathbb Q$ and
$d,h$, and
$R$ be the absolute value of the discriminant, the class number, and the regulator, respectively, of
$K$. It is known that if
$K$ contains no quadratic subfield, then
$$
hR\gg\frac{d^{1/2}}{\log d},
$$
where the implied constant depends only on
$n$. In Theorem 1 this lower estimate is improved for pure cubic fields.
Consider the family
$\mathcal K_n$ where
$K\in\mathcal K_n$ if
$K$ is a totally real number field of degree
$n$ whose normal closure has the symmetric group
$S_n$ as its Galois group. Theorem 2: Fix
$n\ge2$. There are infinitely many
$K\in\mathcal K_n$ with
$$
h\gg d^{1/2}(\log\log d)^{n-1}/(\log d)^n,
$$
where the implied constant depends only on
$n$.
This is a somewhat greater improvement over W. Duke's analogous result with
$h\gg d^{1/2}/(\log d)^n$ [MR 1966783 (2004g:11103)].
Key words and phrases:
class number, Dedekind $\zeta$-function, generalized Riemann hypothesis.
UDC:
511.466+517.863
Received: 15.07.2012