Many previous Sum-of-Squares (SOS) lower bounds for CSPs had two deficiencies related to global constraints. First, they were not able to support a "cardinality constraint", as in, say, the Min-Bisection problem. Second, while the pseudoexpectation of the objective function was shown to have some value beta, it did not necessarily actually "satisfy" the constraint "objective = beta". In this paper we show how to remedy both deficiencies in the case of random CSPs, by translating global constraints into local constraints. Using these ideas, we also show that degree-Omega(sqrt{n}) SOS does not provide a (4/3 - epsilon)-approximation for Min-Bisection, and degree-Omega(n) SOS does not provide a (11/12 + epsilon)-approximation for Max-Bisection or a (5/4 - epsilon)-approximation for Min-Bisection. No prior SOS lower bounds for these problems were known.
@InProceedings{kothari_et_al:LIPIcs.ITCS.2019.49, author = {Kothari, Pravesh K. and O'Donnell, Ryan and Schramm, Tselil}, title = {{SOS Lower Bounds with Hard Constraints: Think Global, Act Local}}, booktitle = {10th Innovations in Theoretical Computer Science Conference (ITCS 2019)}, pages = {49:1--49:21}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-095-8}, ISSN = {1868-8969}, year = {2019}, volume = {124}, editor = {Blum, Avrim}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2019.49}, URN = {urn:nbn:de:0030-drops-101420}, doi = {10.4230/LIPIcs.ITCS.2019.49}, annote = {Keywords: sum-of-squares hierarchy, random constraint satisfaction problems} }
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