| Decodability of group homomorphisms beyond the johnson bound |
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Annual ACM Symposium on Theory of Computing
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Proceedings of the 40th annual ACM symposium on Theory of computing
table of contents
Victoria, British Columbia, Canada
Pages 275-284
Year of Publication: 2008
ISBN:978-1-60558-047-0
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Authors
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Irit Dinur
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Weizmann Institute of Science, Rehovot, Israel
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Elena Grigorescu
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Massachusetts Institute of Technology, Cambridge, MA, USA
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Swastik Kopparty
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Massachusetts Institute of Technology, Cambridge, MA, USA
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Madhu Sudan
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Massachusetts Institute of Technology, Cambridge, MA, USA
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Downloads (6 Weeks): 8, Downloads (12 Months): 68, Citation Count: 1
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ABSTRACT
Given a pair of finite groups G and H, the set of homomorphisms from G to H form an error-correcting code where codewords differ in at least 1/2 the coordinates. We show that for every pair of abelian groups G and H, the resulting code is (locally) list-decodable from a fraction of errors arbitrarily close to its distance. At the heart of this result is the following combinatorial result: There is a fixed polynomial p(•) such that for every pair of abelian groups G and H, if the maximum fraction of agreement between two distinct homomorphisms from G to H is Λ, then for every ε> 0 and every function f:G -> H, the number of homomorphisms that have agreement Λ + ε with f is at most p(1/ε). We thus give a broad class of codes whose list-decoding radius exceeds the "Johnson bound". Examples of such codes are rare in the literature, and for the ones that do exist, "combinatorial" techniques to analyze their list-decodability are limited. Our work is an attempt to add to the body of such techniques. We use the fact that abelian groups decompose into simpler ones and thus codes derived from homomorphisms over abelian groups may be viewed as certain "compositions" of simpler codes. We give techniques to lift list-decoding bounds for the component codes to bounds for the composed code. We believe these techniques may be of general interest.
REFERENCES
Note: OCR errors may be found in this Reference List extracted from the full text article. ACM has opted to expose the complete List rather than only correct and linked references.
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Irit Dinur, Elena Grigorescu, Swastik Kopparty, and Madhu Sudan. Decodability of Group Homomorphisms beyond the Johnson Bound. Electronic Colloquium on Computational Complexity (ECCC), 15(TR08-020), 2008.
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[doi> 10.1145/509907.509933]
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Elena Grigorescu, Swastik Kopparty, and Madhu Sudan. Local decoding and testing for homomorphisms. In APPROX-RANDOM, volume 4110 of Lecture Notes in Computer Science, pages 375--385. Springer, 2006.
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V. Guruswami and M. Sudan. Extensions to the johnson bound, 2001.
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Venkatesan Guruswami and Atri Rudra. Explicit capacity-achieving list-decodable codes. Electronic Colloquium on Computational Complexity (ECCC), (133), 2005.
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Madhu Sudan , Luca Trevisan , Salil Vadhan, Pseudorandom generators without the XOR Lemma (extended abstract), Proceedings of the thirty-first annual ACM symposium on Theory of computing, p.537-546, May 01-04, 1999, Atlanta, Georgia, United States
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A. Ta-Shma and D. Zuckerman. Extractor codes. IEEE Transactions on Information Theory, 50, 2004
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