On the Optimality of Gluing over Scales

  • Authors:
  • Alex Jaffe;James R. Lee;Mohammad Moharrami

  • Affiliations:
  • University of Washington, Seattle, USA 98105;University of Washington, Seattle, USA 98105;University of Washington, Seattle, USA 98105

  • Venue:
  • APPROX '09 / RANDOM '09 Proceedings of the 12th International Workshop and 13th International Workshop on Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques
  • Year:
  • 2009

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Abstract

We show that for every *** 0, there exist n -point metric spaces (X ,d ) where every "scale" admits a Euclidean embedding with distortion at most *** , but the whole space requires distortion at least $\Omega(\sqrt{\alpha \log n})$. This shows that the scale-gluing lemma [Lee, SODA 2005] is tight, and disproves a conjecture stated there. This matching upper bound was known to be tight at both endpoints, i.e. when *** = ***(1) and *** = ***(logn ), but nowhere in between. More specifically, we exhibit n -point spaces with doubling constant *** requiring Euclidean distortion $\Omega(\sqrt{\log \lambda \log n})$, which also shows that the technique of "measured descent" [Krauthgamer, et. al., Geometric and Functional Analysis ] is optimal. We extend this to L p spaces with p 1, where one requires distortion at least ***((logn )1/q (log*** )1 *** 1/q ) when q = max {p ,2}, a result which is tight for every p 1.