The second moment of the size of the $2$-class group of monogenized cubic fields

Fuente: arXiv
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Main Authors: Bhargava, Manjul, Shankar, Arul, Swaminathan, Ashvin
Format: Preprint
Published: 2025
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_version_ 1866909639657914368
author Bhargava, Manjul
Shankar, Arul
Swaminathan, Ashvin
author_facet Bhargava, Manjul
Shankar, Arul
Swaminathan, Ashvin
contents We prove that when totally real (resp., complex) monogenized cubic number fields are ordered by height, the second moment of the size of the $2$-class group is at most $3$ (resp., at most $6$). In the totally real case, we further prove that the second moment of the size of the narrow $2$-class group is at most $9$. This result gives further evidence in support of the general observation, first made in work of Bhargava--Hanke--Shankar and recently formalized into a set of heuristics in work of Siad--Venkatesh, that monogenicity has an altering effect on class group distributions. All of the upper bounds we obtain are tight, conditional on tail estimates.
format Preprint
id arxiv_https___arxiv_org_abs_2506_05539
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The second moment of the size of the $2$-class group of monogenized cubic fields
Bhargava, Manjul
Shankar, Arul
Swaminathan, Ashvin
Number Theory
11R16, 11R29, 11R45
We prove that when totally real (resp., complex) monogenized cubic number fields are ordered by height, the second moment of the size of the $2$-class group is at most $3$ (resp., at most $6$). In the totally real case, we further prove that the second moment of the size of the narrow $2$-class group is at most $9$. This result gives further evidence in support of the general observation, first made in work of Bhargava--Hanke--Shankar and recently formalized into a set of heuristics in work of Siad--Venkatesh, that monogenicity has an altering effect on class group distributions. All of the upper bounds we obtain are tight, conditional on tail estimates.
title The second moment of the size of the $2$-class group of monogenized cubic fields
topic Number Theory
11R16, 11R29, 11R45
url https://arxiv.org/abs/2506.05539