On the Quotient of a Pseudo-null Module
Abstract
Motivated by questions arising in noncommutative Iwasawa theory, let R be a (not necessarily commutative) ring, T ∈ R a regular central element, and M a pseudo-null R-module. We investigate necessary and sufficient conditions under which the quotient M/TM is pseudo-null as an R/TR-module. We first give necessary and sufficient conditions in terms of associated prime ideals when R is commutative. Then we apply this to the case when R is a Krull domain and obtain a precise relationship between the characteristic ideals of M/TM and the T-torsion submodule M[T]. We give necessary and sufficient conditions in terms of Ext groups when R is a noncommutative ring and then compare them with the criterion when R is commutative. Lastly, we give an application to noncommutative Iwasawa theory. Roughly speaking, if `big' dual fine Selmer group is pseudo-null, then `most' specialized dual fine Selmer group is pseudo-null.
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BibTeX
@misc{qi2026quotient,
title = {{On the Quotient of a Pseudo-null Module}},
author = {Peikai Qi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39655},
eprint = {2609.39655},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39655},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - On the Quotient of a Pseudo-null Module
AU - Peikai Qi
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39655
UR - https://arxiv.org/abs/2609.39655
AB - Motivated by questions arising in noncommutative Iwasawa theory, let R be a (not necessarily commutative) ring, T ∈ R a regular central element, and M a pseudo-null R-module. We investigate necessary and sufficient conditions under which the quotient M/TM is pseudo-null as an R/TR-module. We first give necessary and sufficient conditions in terms of associated prime ideals when R is commutative. Then we apply this to the case when R is a Krull domain and obtain a precise relationship between the characteristic ideals of M/TM and the T-torsion submodule M[T]. We give necessary and sufficient conditions in terms of Ext groups when R is a noncommutative ring and then compare them with the criterion when R is commutative. Lastly, we give an application to noncommutative Iwasawa theory. Roughly speaking, if `big' dual fine Selmer group is pseudo-null, then `most' specialized dual fine Selmer group is pseudo-null.
ER -