A completeness theory for polynomial (Turing) kernelization

Danny Hermelin, Stefan Kratsch, Karolina Sołtys, Magnus Wahlström, Xi Wu

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

10 Scopus citations


The framework of Bodlaender et al. (ICALP 2008, JCSS 2009) and Fortnow and Santhanam (STOC 2008, JCSS 2011) allows us to exclude the existence of polynomial kernels for a range of problems under reasonable complexity- theoretical assumptions. However, some issues are not addressed by this framework, including the existence of Turing kernels such as the "kernelization" of Leaf Out Branching(k) into a disjunction over n instances each of size poly(k). Observing that Turing kernels are preserved by polynomial parametric transformations (PPTs), we define two kernelization hardness hierarchies by the PPT-closure of problems that seem fundamentally unlikely to admit efficient Turing kernelizations. This gives rise to the MK- and WK-hierarchies which are akin to the M- and W-hierarchies of ordinary parameterized complexity. We find that several previously considered problems are complete for the fundamental hardness class WK[1], including Min Ones d -SAT(k), Binary NDTM Halting(k), Connected Vertex Cover(k), and Clique parameterized by k logn. We conjecture that no WK[1]-hard problem admits a polynomial Turing kernel. Our hierarchy subsumes an earlier hierarchy of Harnik and Naor (FOCS 2006, SICOMP 2010) that, from a parameterized perspective, is restricted to classical problems parameterized by witness size. Our results provide the first natural complete problems for, e.g., their class VC 1; this had been left open.

Original languageEnglish
Title of host publicationParameterized and Exact Computation - 8th International Symposium, IPEC 2013, Revised Selected Papers
Number of pages14
StatePublished - 1 Dec 2013
Event8th International Symposium on Parameterized and Exact Computation, IPEC 2013 - Sophia Antipolis, France
Duration: 4 Sep 20136 Sep 2013

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume8246 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference8th International Symposium on Parameterized and Exact Computation, IPEC 2013
CitySophia Antipolis

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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