Tension Bounds for Information Complexity

The main contribution of this work is to relate information complexity to “tension” [PP14] – an informationtheoretic quantity defined with no reference to protocols – and to illustrate that it allows deriving strong lower-bounds on information complexity. In particular, we use a very special case of this connection to give a quantitatively tighter connection between information complexity and discrepancy than the one in [BW12] (albeit, restricted to independent inputs). Further, as tension is in fact a multi-dimensional notion, it enables us to bound the 2-dimensional region that represents the trade-off between the amounts of communication in the two directions, in a 2-party protocol. This work is also intended to highlight tension as a fundamental measure of correlation between a pair of random variables, with rich connections to a variety of questions in computer science and information theory. ∗Department of Computer Science, University of Illinois, Urbana-Champaign. [email protected]. †School of Technology and Computer Science, Tata Institute of Fundamental Research, Mumbai, India. [email protected] ar X iv :1 40 8. 62 85 v1 [ cs .C C ] 2 7 A ug 2 01 4