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PreprintCC BY-SA 4.0arXiv

Optimal Sparsifiers for Abelian Cayley Graphs

Abstract

We prove that for every Cayley graph 𝒒 over any finite abelian group G, there is a weighted Cayley graph with O(log |G|) generators that is a spectral sparsifier for 𝒒. This bound is optimal. Applying our bound to the group G = 𝔽2n, yields, as a corollary, O(n/Ξ΅2)-sized code sparsifiers for 𝔽2-linear codes, improving on the work of Khanna, Putterman and Sudan (SODA'24) who obtained a similar result with an additional polylog(n) loss. Our proof is strongly inspired by a recent work of Reis and Rothvoss for the construction of β„“1-sparsifiers. Following their work, the abelian Cayley sparsification problem can be reduced to establishing a lower bound for the volume of a certain natural convex body. This volume bound follows from a short, elementary argument that relies on character symmetry.

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BibTeX
@misc{basu2026optimal,
  title = {{Optimal Sparsifiers for Abelian Cayley Graphs}},
  author = {Arpon Basu and Pravesh K. Kothari and Raghu Meka and Stefan Tudose},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2607.08261},
  eprint = {2607.08261},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.08261},
  note = {CC BY-SA 4.0},
}
RIS
TY  - UNPB
TI  - Optimal Sparsifiers for Abelian Cayley Graphs
AU  - Arpon Basu
AU  - Pravesh K. Kothari
AU  - Raghu Meka
AU  - Stefan Tudose
PY  - 2026
DA  - 2026/11/03
PB  - arXiv
DO  - 10.48550/arxiv.2607.08261
UR  - https://arxiv.org/abs/2607.08261
AB  - We prove that for every Cayley graph 𝒒 over any finite abelian group G, there is a weighted Cayley graph with O(log |G|) generators that is a spectral sparsifier for 𝒒. This bound is optimal. Applying our bound to the group G = 𝔽_2^n, yields, as a corollary, O(n/Ξ΅^2)-sized code sparsifiers for 𝔽_2-linear codes, improving on the work of Khanna, Putterman and Sudan (SODA'24) who obtained a similar result with an additional polylog(n) loss. Our proof is strongly inspired by a recent work of Reis and Rothvoss for the construction of β„“_1-sparsifiers. Following their work, the abelian Cayley sparsification problem can be reduced to establishing a lower bound for the volume of a certain natural convex body. This volume bound follows from a short, elementary argument that relies on character symmetry.
ER  -