A Rank-Preserving Gaifman Normal Form for First-Order Logic on Weighted Structures
Abstract
We prove a rank-preserving version of Gaifman's Theorem. Compared to earlier rank-preserving locality theorems (in particular, [Grohe, Kreutzer, Siebertz, JACM 2017]), our theorem is much simpler and yields formulas in exactly the same normal form as Gaifman's original theorem. Furthermore, it holds not only for first-order logic, but also for first-order logic with modulo-counting quantifiers and, more generally, for the first-order logic on weighted structures ngFOW+ that is introduced in this article. As an application of our theorem, we give a simplified proof of the algorithmic meta-theorem of [Grohe, Kreutzer, Siebertz, JACM 2017] stating that first-order properties of nowhere dense structures can be decided in almost-linear time. Our locality theorem for the weight logic ngFOW+ can be seen as an essential step toward such a meta-theorem for this logic.
Related
BibTeX
@misc{bergerem2026rankpreserving,
title = {{A Rank-Preserving Gaifman Normal Form for First-Order Logic on Weighted Structures}},
author = {Steffen van Bergerem and Martin Grohe and Charlotte Lenz and Nicole Schweikardt},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37337},
eprint = {2609.37337},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37337},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Rank-Preserving Gaifman Normal Form for First-Order Logic on Weighted Structures
AU - Steffen van Bergerem
AU - Martin Grohe
AU - Charlotte Lenz
AU - Nicole Schweikardt
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37337
UR - https://arxiv.org/abs/2609.37337
AB - We prove a rank-preserving version of Gaifman's Theorem. Compared to earlier rank-preserving locality theorems (in particular, [Grohe, Kreutzer, Siebertz, JACM 2017]), our theorem is much simpler and yields formulas in exactly the same normal form as Gaifman's original theorem. Furthermore, it holds not only for first-order logic, but also for first-order logic with modulo-counting quantifiers and, more generally, for the first-order logic on weighted structures ngFOW+ that is introduced in this article. As an application of our theorem, we give a simplified proof of the algorithmic meta-theorem of [Grohe, Kreutzer, Siebertz, JACM 2017] stating that first-order properties of nowhere dense structures can be decided in almost-linear time. Our locality theorem for the weight logic ngFOW+ can be seen as an essential step toward such a meta-theorem for this logic.
ER -