Near-Optimal Cayley Expanders for Abelian Groups

Authors Akhil Jalan, Dana Moshkovitz

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Akhil Jalan
  • Department of Computer Science, University of Texas at Austin, TX, USA
Dana Moshkovitz
  • Department of Computer Science, University of Texas at Austin, TX, USA

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Akhil Jalan and Dana Moshkovitz. Near-Optimal Cayley Expanders for Abelian Groups. In 41st IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 213, pp. 24:1-24:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


We give an efficient deterministic algorithm that outputs an expanding generating set for any finite abelian group. The size of the generating set is close to the randomized construction of Alon and Roichman [Alon and Roichman, 1994], improving upon various deterministic constructions in both the dependence on the dimension and the spectral gap. By obtaining optimal dependence on the dimension we resolve a conjecture of Azar, Motwani, and Naor [Azar et al., 1998] in the affirmative. Our technique is an extension of the bias amplification technique of Ta-Shma [Ta-Shma, 2017], who used random walks on expanders to obtain expanding generating sets over the additive group of 𝔽₂ⁿ. As a consequence, we obtain (i) randomness-efficient constructions of almost k-wise independent variables, (ii) a faster deterministic algorithm for the Remote Point Problem, (iii) randomness-efficient low-degree tests, and (iv) randomness-efficient verification of matrix multiplication.

Subject Classification

ACM Subject Classification
  • Theory of computation → Pseudorandomness and derandomization
  • Theory of computation → Error-correcting codes
  • Cayley graphs
  • Expander walks
  • Epsilon-biased sets
  • Derandomization


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