Murtagh, JackReingold, OmerSidford, AaronVadhan, Salil2018-01-052017Murtagh, Jack, Omer Reingold, Aaron Sidford, Salil Vadhan. 2017. Derandomization Beyond Connectivity: Undirected Laplacian Systems in Nearly Logarithmic Space. In Proceedings of the 58th Symposium on Foundations of Computer Science (FOCS 2017), Berkeley, CA, October 15-17, 2017.0272-5428http://nrs.harvard.edu/urn-3:HUL.InstRepos:34604534We give a deterministic O˜(log n)-space algorithm for approximately solving linear systems given by Laplacians of undirected graphs, and consequently also approximating hitting times, commute times, and escape probabilities for undirected graphs. Previously, such systems were known to be solvable by randomized algorithms using O(log n) space (Doron, Le Gall, and Ta-Shma, 2017) and hence by deterministic algorithms using O(log3/2 n) space (Saks and Zhou, FOCS 1995 and JCSS 1999). Our algorithm combines ideas from time-efficient Laplacian solvers (Spielman and Teng, STOC ‘04; Peng and Spielman, STOC ‘14) with ideas used to show that UNDIRECTED S-T CONNECTIVITY is in deterministic logspace (Reingold, STOC ‘05 and JACM ‘08; Rozenman and Vadhan, RANDOM ‘05).en-USConference Paper2017-09-1720172018-01-0510.1109/FOCS.2017.79