Abstract
It is known that the extension complexity of the TSP polytope for the complete graph \(K_n\) is exponential in n even if the subtour inequalities are excluded. In this article we study the polytopes formed by removing other subsets \({\mathcal {H}}\) of facet-defining inequalities of the TSP polytope. In particular, we consider the case when \({\mathcal {H}}\) is either the set of blossom inequalities or the simple comb inequalities. These inequalities are routinely used in cutting plane algorithms for the TSP. We show that the extension complexity remains exponential even if we exclude these inequalities. In addition we show that the extension complexity of polytope formed by all comb inequalities is exponential. For our proofs, we introduce a subclass of comb inequalities, called (h, t)-uniform inequalities, which may be of independent interest.
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Notes
W. Cook (private communication) attributes the same argument to T. Rothvoß.
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Acknowledgments
Research of the first author is supported by a Grant-in-Aid for Scientific Research on Innovative Areas—Exploring the Limits of Computation, MEXT, Japan. Research of the second author is partially supported by GA ČR Grant P202-13/201414.
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Avis, D., Tiwary, H.R. On the \({\mathcal {H}}\)-free extension complexity of the TSP. Optim Lett 11, 445–455 (2017). https://doi.org/10.1007/s11590-016-1029-1
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DOI: https://doi.org/10.1007/s11590-016-1029-1