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Transactions of the American Mathematical Society

Published by the American Mathematical Society since 1900, Transactions of the American Mathematical Society is devoted to longer research articles in all areas of pure and applied mathematics.

ISSN 1088-6850 (online) ISSN 0002-9947 (print)

The 2020 MCQ for Transactions of the American Mathematical Society is 1.48.

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When does a perturbation of the equations preserve the normal cone?
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by Pham Hung Quy and Ngo Viet Trung HTML | PDF
Trans. Amer. Math. Soc. 376 (2023), 4957-4978 Request permission


Let $(R,\frak {m})$ be a local ring and $I, J$ two arbitrary ideals of $R$. Let $gr_J(R/I)$ denote the associated graded ring of $R/I$ with respect to $J$, which corresponds to the normal cone in algebraic geometry. With regards to the finite determinacy of singularity with respect to the Jacobian ideal we study the problem for which ideal $I = (f_1,\dots ,f_r)$ does there exist a number $N$ such that if $f_i’ \equiv f_i \mod J^N$, $i = 1,\dots ,r$, and $I’ = (f_1’,\dots ,f_r’)$, then $gr_J(R/I) \cong gr_J(R/I’)$. This problem arises from a recent result of Ma, Quy and Smirnov in the case $J$ is an $\frak {m}$-primary ideal, which solves a long standing conjecture of Srinivas and Trivedi on the invariance of Hilbert functions under small perturbations. Their approach involves Hilbert functions and cannot be used to study the above general problem. Our main result shows that such a number $N$ exists if $f_1,\dots ,f_r$ is locally a regular sequence outside the locus of $J$. It has interesting applications to a range of related problems.
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Additional Information
  • Pham Hung Quy
  • Affiliation: Department of Mathematics, FPT University, Hanoi, Vietnam
  • MR Author ID: 894036
  • ORCID: 0000-0002-3317-0191
  • Email:
  • Ngo Viet Trung
  • Affiliation: International Centre for Research and Postgraduate Training, Institute of Mathematics, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
  • MR Author ID: 207806
  • Email:
  • Received by editor(s): February 18, 2022
  • Received by editor(s) in revised form: December 28, 2022
  • Published electronically: April 12, 2023
  • Additional Notes: This work was supported by grant NCXS02.01/22-23 of Vietnam Academy of Science and Technology.
  • © Copyright 2023 American Mathematical Society
  • Journal: Trans. Amer. Math. Soc. 376 (2023), 4957-4978
  • MSC (2020): Primary 13A30, 13D10; Secondary 13H15, 13P10, 14B12
  • DOI: