2018 IEEE 59th Annual Symposium on Foundations of Computer Science A Matrix Chernoff Bound for Strongly Rayleigh Distributions and Spectral Sparsifiers from a few Random Spanning Trees Rasmus Kyng Zhao Song School of Engineering and Applied Sciences School of Engineering and Applied Sciences Harvard University Harvard University Cambridge, MA, USA Cambridge, MA, USA
[email protected] [email protected] Abstract— usually being measured by spectral norm. Modern quantita- Strongly Rayleigh distributions are a class of negatively tive bounds of the form often used in theoretical computer dependent distributions of binary-valued random variables science were derived by for example by Rudelson [Rud99], [Borcea, Brändén, Liggett JAMS 09]. Recently, these distribu- tions have played a crucial role in the analysis of algorithms for while Ahlswede and Winter [AW02] established a useful fundamental graph problems, e.g. Traveling Salesman Problem matrix-version of the Laplace transform that plays a central [Gharan, Saberi, Singh FOCS 11]. We prove a new matrix role in scalar concentration results such as those of Bern- Chernoff bound for Strongly Rayleigh distributions. stein. [AW02] combined this with the Golden-Thompson As an immediate application, we show that adding together − trace inequality to prove matrix concentration results. Tropp the Laplacians of 2 log2 n random spanning trees gives an (1 ± ) spectral sparsifiers of graph Laplacians with high refined this approach, and by replacing the use of Golden- probability. Thus, we positively answer an open question posted Thompson with deep a theorem on concavity of certain trace in [Baston, Spielman, Srivastava, Teng JACM 13]. Our number functions due to Lieb, Tropp was able to recover strong of spanning trees for spectral sparsifier matches the number versions of a wide range of scalar concentration results, of spanning trees required to obtain a cut sparsifier in [Fung, including matrix Chernoff bounds, Azuma and Freedman’s Hariharan, Harvey, Panigraphi STOC 11].