Title
Sign-rank Can Increase under Intersection
Abstract
AbstractThe communication class UPPcc is a communication analog of the Turing Machine complexity class PP. It is characterized by a matrix-analytic complexity measure called sign-rank (also called dimension complexity), and is essentially the most powerful communication class against which we know how to prove lower bounds.For a communication problem f, let f ∧ f denote the function that evaluates f on two disjoint inputs and outputs the AND of the results. We exhibit a communication problem f with UPPcc(f) = O(log n), and UPPcc(f ∧ f) = Θ (log2 n). This is the first result showing that UPP communication complexity can increase by more than a constant factor under intersection. We view this as a first step toward showing that UPPcc, the class of problems with polylogarithmic-cost UPP communication protocols, is not closed under intersection.Our result shows that the function class consisting of intersections of two majorities on n bits has dimension complexity nOmegaΩ(log n). This matches an upper bound of (Klivans, O’Donnell, and Servedio, FOCS 2002), who used it to give a quasipolynomial time algorithm for PAC learning intersections of polylogarithmically many majorities. Hence, fundamentally new techniques will be needed to learn this class of functions in polynomial time.
Year
DOI
Venue
2021
10.1145/3470863
ACM Transactions on Computation Theory
Keywords
DocType
Volume
Sign rank, dimension complexity, communication complexity, learning theory
Journal
13
Issue
ISSN
Citations 
4
1942-3454
0
PageRank 
References 
Authors
0.34
0
3
Name
Order
Citations
PageRank
Mark Bun114315.05
Mande Nikhil S.254.13
Thaler Justin327320.17