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Randomness conductors and constant-degree lossless expanders
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Source Annual ACM Symposium on Theory of Computing archive
Proceedings of the thiry-fourth annual ACM symposium on Theory of computing table of contents
Montreal, Quebec, Canada
SESSION: Session 11A table of contents
Pages: 659 - 668  
Year of Publication: 2002
ISBN:1-58113-495-9
Authors
Michael Capalbo  Institute for Advanced Study, Princeton, NJ
Omer Reingold  AT&T Labs - Research, Florham Park, NJ
Salil Vadhan  Harvard University, Cambridge, MA
Avi Wigderson  Hebrew University, Jerusalem and Institute for Advanced Study, Princeton, NJ
Sponsor
SIGACT: ACM Special Interest Group on Algorithms and Computation Theory
Publisher
ACM  New York, NY, USA
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ABSTRACT

The main concrete result of this paper is the first explicit construction of constant degree lossless expanders. In these graphs, the expansion factor is almost as large as possible: (1—&egr;)D, where D is the degree and &egr; is an arbitrarily small constant. The best previous explicit constructions gave expansion factor D/2, which is too weak for many applications. The D/2 bound was obtained via the eigenvalue method, and is known that that method cannot give better bounds.The main abstract contribution of this paper is the introduction and initial study of randomness conductors, a notion which generalizes extractors, expanders, condensers and other similar objects. In all these functions, certain guarantee on the input "entropy" is converted to a guarantee on the output "entropy". For historical reasons, specific objects used specific guarantees of different flavors. We show that the flexibility afforded by the conductor definition leads to interesting combinations of these objects, and to better constructions such as those above.The main technical tool in these constructions is a natural generalization to conductors of the zig-zag graph product, previously defined for expanders and extractors.


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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CITED BY  17

Collaborative Colleagues:
Michael Capalbo: colleagues
Omer Reingold: colleagues
Salil Vadhan: colleagues
Avi Wigderson: colleagues