A Probabilistic Inequality with Applications to Threshold Direct-Product Theorems

  • Authors:
  • Falk Unger

  • Affiliations:
  • -

  • Venue:
  • FOCS '09 Proceedings of the 2009 50th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2009

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Abstract

We prove a simple concentration inequality, which is an extension of the Chernoff bound and Hoeffding's inequality for binary random variables. Instead of assuming independence of the variables we use a slightly weaker condition, namely bounds on the co-moments. This inequality allows us to simplify and strengthen several known direct-product theorems and establish new threshold direct-product theorems. Threshold direct-product theorems are statements of the following form: If one instance of a problem can be solved with probability at most p, then solving significantly more than a p-fraction among multiple instances has negligible probability. Results of this kind are crucial when distinguishing whether a process succeeds with probability s or c, for 0