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The canonical problem that gives an exponential separation between deterministic and randomized communication complexity in the classical two-party communication model is "Equality". In this work we show that even allowing access to an "Equality" oracle, deterministic protocols remain exponentially weaker than randomized ones. More precisely, we exhibit a total function on n bits with randomized one-sided communication complexity O(log n), but such that every deterministic protocol with access to "Equality" oracle needs Omega(n) cost to compute it.
Additionally we exhibit a natural and strict infinite hierarchy within BPP, starting with the class P^{EQ} at its bottom.
@InProceedings{chattopadhyay_et_al:LIPIcs.CCC.2019.14,
author = {Chattopadhyay, Arkadev and Lovett, Shachar and Vinyals, Marc},
title = {{Equality Alone Does not Simulate Randomness}},
booktitle = {34th Computational Complexity Conference (CCC 2019)},
pages = {14:1--14:11},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-116-0},
ISSN = {1868-8969},
year = {2019},
volume = {137},
editor = {Shpilka, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2019.14},
URN = {urn:nbn:de:0030-drops-108368},
doi = {10.4230/LIPIcs.CCC.2019.14},
annote = {Keywords: Communication lower bound, derandomization}
}