The power series Dedekind-Mertens number

Thieu N. Vo, Phan Thanh Toan

Research output: Contribution to journalArticlepeer-review

1 Citation (SciVal)

Abstract

Let (Formula presented.) and (Formula presented.) be the polynomial ring and the power series ring, respectively, over a commutative ring R with identity. For (Formula presented.), let Af be the ideal of R generated by the coefficients of f. If g is a polynomial in (Formula presented.), then the Dedekind-Mertens number (Formula presented.) is the least positive integer k such that (Formula presented.) for every polynomial (Formula presented.). For a power series (Formula presented.), we define the power series Dedekind-Mertens number (Formula presented.) to be the least positive integer k (if any) such that (Formula presented.) for every power series (Formula presented.). Heinzer and Huneke showed that if (Formula presented.), then (Formula presented.) - (Formula presented.), where l- (Formula presented.) is the locally minimal number of generators of Ag. Surprisingly, for (Formula presented.), Epstein and Shapiro obtained a similar result that (Formula presented.) - (Formula presented.) provided that the ring R is Noetherian. They asked whether the same result still holds for an arbitrary ring Park, Kang, and Toan gave a negative answer to this question and further proved that if (Formula presented.), then (Formula presented.) - (Formula presented.), where l- (Formula presented.) is the locally minimal number of special generators of Ag. Note that we always have l- (Formula presented.) - (Formula presented.) for every power series (Formula presented.). In this paper, we show that there is a ring R with power series (Formula presented.) such that (Formula presented.) - (Formula presented.) while l- (Formula presented.) can be arbitrarily larger than l- (Formula presented.). In other words, the upper bound l- (Formula presented.) for (Formula presented.) is sharp and l- (Formula presented.) and (Formula presented.) are in general unrelated to the number l- (Formula presented.). This gives a complete answer to the question by Epstein and Shapiro.

Original languageEnglish
Pages (from-to)3481-3489
Number of pages9
JournalCommunications in Algebra
Volume47
Issue number9
DOIs
Publication statusPublished - 31 Dec 2019

Keywords

  • Content ideal
  • Dedekind-Mertens number
  • polynomial ring
  • power series ring

ASJC Scopus subject areas

  • Algebra and Number Theory

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