TY - JOUR

T1 - Efficient Removal Lemmas for Matrices

AU - Alon, Noga

AU - Ben-Eliezer, Omri

N1 - Funding Information:
Research supported in part by NSF grant DMS-1855464, ISF grant 281/17, GIF grant G-1347-304.6/2016, and the Simons Foundation. Acknowledgments
Publisher Copyright:
© 2019, Springer Nature B.V.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/4/1

Y1 - 2020/4/1

N2 - It was recently proved in Alon et al. (2017) that any hereditary property of two-dimensional matrices (where the row and column order is not ignored) over a finite alphabet is testable with a constant number of queries, by establishing the following ordered matrix removal lemma: For any finite alphabet Γ, any hereditary property P of matrices over Γ, and any ϵ > 0, there exists fP such that for any matrix M over Γ that is ϵ-far from satisfying P, most of the fP × fP submatrices of M do not satisfy P. Here being ϵ-far from P means that one needs to modify at least an ϵ-fraction of the entries of M to make it satisfy P. However, in the above general removal lemma, fP grows very quickly as a function of ϵ− 1, even when P is characterized by a single forbidden submatrix. In this work we establish much more efficient removal lemmas for several special cases of the above problem. In particular, we show the following, which can be seen as an efficient binary matrix analogue of the triangle removal lemma: For any fixed s × t binary matrix A and any ϵ > 0 there exists δ > 0 polynomial in ϵ, such that for any binary matrix M in which less than a δ-fraction of the s × t submatrices are equal to A, there exists a set of less than an ϵ-fraction of the entries of M that intersects every copy of A in M. We generalize the work of Alon et al. (2007) and make progress towards proving one of their conjectures. The proofs combine their efficient conditional regularity lemma for matrices with additional combinatorial and probabilistic ideas.

AB - It was recently proved in Alon et al. (2017) that any hereditary property of two-dimensional matrices (where the row and column order is not ignored) over a finite alphabet is testable with a constant number of queries, by establishing the following ordered matrix removal lemma: For any finite alphabet Γ, any hereditary property P of matrices over Γ, and any ϵ > 0, there exists fP such that for any matrix M over Γ that is ϵ-far from satisfying P, most of the fP × fP submatrices of M do not satisfy P. Here being ϵ-far from P means that one needs to modify at least an ϵ-fraction of the entries of M to make it satisfy P. However, in the above general removal lemma, fP grows very quickly as a function of ϵ− 1, even when P is characterized by a single forbidden submatrix. In this work we establish much more efficient removal lemmas for several special cases of the above problem. In particular, we show the following, which can be seen as an efficient binary matrix analogue of the triangle removal lemma: For any fixed s × t binary matrix A and any ϵ > 0 there exists δ > 0 polynomial in ϵ, such that for any binary matrix M in which less than a δ-fraction of the s × t submatrices are equal to A, there exists a set of less than an ϵ-fraction of the entries of M that intersects every copy of A in M. We generalize the work of Alon et al. (2007) and make progress towards proving one of their conjectures. The proofs combine their efficient conditional regularity lemma for matrices with additional combinatorial and probabilistic ideas.

KW - Matrix properties

KW - Property testing

KW - Removal lemma

KW - Submatrix freeness

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U2 - 10.1007/s11083-019-09494-3

DO - 10.1007/s11083-019-09494-3

M3 - Article

AN - SCOPUS:85089533973

VL - 37

SP - 83

EP - 101

JO - Order

JF - Order

SN - 0167-8094

IS - 1

ER -