Improved lower bounds on the randomized complexity of graph properties

  • Authors:
  • Amit Chakrabarti;Subhash Khot

  • Affiliations:
  • Computer Science Department, Dartmouth College, Hanover, New Hampshire 03755;College of Computing, Georgia Institute of Technology, 801 Atlantic Drive, Atlanta, Georgia 30332

  • Venue:
  • Random Structures & Algorithms
  • Year:
  • 2007

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Abstract

We prove a lower bound of Ω(n4/3 log 1/3n) on the randomized decision tree complexity of any nontrivial monotone n-vertex graph property, and of any nontrivial monotone bipartite graph property with bipartitions of size n. This improves the previous best bound of Ω(n4/3) due to Hajnal (Combinatorica 11 (1991) 131–143). Our proof works by improving a graph packing lemma used in earlier work, and this improvement in turn stems from a novel probabilistic analysis. Graph packing being a well-studied subject in its own right, our improved packing lemma and the probabilistic technique used to prove it may be of independent interest. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2007 A shorter preliminary version of this paper appeared in the Proceedings of ICALP 2001, the 28th International Colloquium on Automata, Languages and Programming, Heraklion, Greece.