Frobenius splitting of valuation rings revisited
Abstract
Let K be a function field over an F-finite field k of characteristic p > 0 and let ν be a valuation of K/k. We show ν is an Abhyankar valuation of K/k if and only if the corresponding valuation ring is Frobenius split. The proof proceeds by analyzing when ideals of a valuation ring are uniformly F-compatible and establishing a general ramification-theoretic characterization of Frobenius split valuation rings of F-finite fields. In addition, when the ground field k is not F-finite, we show that the equivalence between Frobenius splitting and the Abhyankar property can fail by constructing an example of an excellent Frobenius split DVR of a function field whose corresponding valuation is not divisorial. Our methods do not rely on local uniformization results.
Related
BibTeX
@misc{datta2026frobenius,
title = {{Frobenius splitting of valuation rings revisited}},
author = {Rankeya Datta and Karen E. Smith},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11032},
eprint = {2610.11032},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11032},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Frobenius splitting of valuation rings revisited
AU - Rankeya Datta
AU - Karen E. Smith
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11032
UR - https://arxiv.org/abs/2610.11032
AB - Let K be a function field over an F-finite field k of characteristic p > 0 and let ν be a valuation of K/k. We show ν is an Abhyankar valuation of K/k if and only if the corresponding valuation ring is Frobenius split. The proof proceeds by analyzing when ideals of a valuation ring are uniformly F-compatible and establishing a general ramification-theoretic characterization of Frobenius split valuation rings of F-finite fields. In addition, when the ground field k is not F-finite, we show that the equivalence between Frobenius splitting and the Abhyankar property can fail by constructing an example of an excellent Frobenius split DVR of a function field whose corresponding valuation is not divisorial. Our methods do not rely on local uniformization results.
ER -