Kernel bounds for disjoint cycles and disjoint paths

  • Authors:

  • Hans L. Bodlaender;Stéphan Thomassé;Anders Yeo

  • Affiliations:

  • Department of Computer Science, Utrecht University, 3508 TB Utrecht, Netherlands;LIRMM-Université Montpellier II, 161 Rue Ada, 34392 Montpellier Cedex, France;Department of Computer Science, Royal Holloway University of London, Egham, Surrey TW20 OEX, United Kingdom

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2011

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Abstract

In this paper, we show that the problems Disjoint Cycles and Disjoint Paths do not have polynomial kernels, unless NP@?coNP/poly. Thus, these problems do not allow polynomial time preprocessing that results in instances whose size is bounded by a polynomial in the parameter at hand. We build upon recent results by Bodlaender et al. [6] and Fortnow and Santhanam [20], that show that NP-complete problems that are 'or-compositional' do not have polynomial kernels, unless NP@?coNP/poly. To this machinery, we add a notion of transformation, and obtain that Disjoint Cycles, and Disjoint Paths do not have polynomial kernels, unless NP@?coNP/poly. For the proof, we introduce a problem on strings, called Disjoint Factors, and first show that this problem has no polynomial kernel unless NP@?coNP/poly. We also show that the related Disjoint Cycles Packing problem has a kernel of size O(klogk).