We give a combinatorial analysis (using edge expansion) of a variant of the iterative expander construction due to Reingold, Vadhan, and Wigderson (2002), and show that this analysis can be formalized in the bounded arithmetic system VNC^1 (corresponding to the "NC^1 reasoning"). As a corollary, we prove the assumption made by Jerabek (2011) that a construction of certain bipartite expander graphs can be formalized in VNC^1. This in turn implies that every proof in Gentzen's sequent calculus LK of a monotone sequent can be simulated in the monotone version of LK (MLK) with only polynomial blowup in proof size, strengthening the quasipolynomial simulation result of Atserias, Galesi, and Pudlak (2002).
@InProceedings{buss_et_al:LIPIcs.ITCS.2017.31, author = {Buss, Sam and Kabanets, Valentine and Kolokolova, Antonina and Koucky, Michal}, title = {{Expander Construction in VNC1}}, booktitle = {8th Innovations in Theoretical Computer Science Conference (ITCS 2017)}, pages = {31:1--31:26}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-029-3}, ISSN = {1868-8969}, year = {2017}, volume = {67}, editor = {Papadimitriou, Christos H.}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2017.31}, URN = {urn:nbn:de:0030-drops-81871}, doi = {10.4230/LIPIcs.ITCS.2017.31}, annote = {Keywords: expander graphs, bounded arithmetic, alternating log time, sequent calculus, monotone propositional logic} }
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