Spectral Algorithms for Unique Games

  • Authors:
  • Alexandra Kolla

  • Affiliations:
  • -

  • Venue:
  • CCC '10 Proceedings of the 2010 IEEE 25th Annual Conference on Computational Complexity
  • Year:
  • 2010

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Abstract

We present a new algorithm for Unique Games which is based on purely {\em spectral} techniques, in contrast to previous work in the area, which relies heavily on semidefinite programming (SDP). Given a highly satisfiable instance of Unique Games, our algorithm is able to recover a good assignment. The approximation guarantee depends only on the completeness of the game, and not on the alphabet size, while the running time depends on spectral properties of the {\em Label-Extended} graph associated with the instance of Unique Games. In particular, we show how our techniques imply a quasi-polynomial time algorithm that decides satisfiability of a game on the Khot-Vishnoi\cite{KV} integrality gap instance. Notably, when run on that instance, the standard SDP relaxation of Unique Games {\em fails}. As a special case, we also show how to re-derive a polynomial time algorithm for Unique Games on expander constraint graphs (similar to \cite{AKKTSV}) and a sub-exponential time algorithm for Unique Games on the Hypercube.