We prove that throughout the satisfiable phase, the logarithm of the number of satisfying assignments of a random 2-SAT formula satisfies a central limit theorem. This implies that the log of the number of satisfying assignments exhibits fluctuations of order √n, with n the number of variables. The formula for the variance can be evaluated effectively. By contrast, for numerous other random constraint satisfaction problems the typical fluctuations of the logarithm of the number of solutions are bounded throughout all or most of the satisfiable regime.
@InProceedings{chatterjee_et_al:LIPIcs.APPROX/RANDOM.2024.39, author = {Chatterjee, Arnab and Coja-Oghlan, Amin and M\"{u}ller, Noela and Riddlesden, Connor and Rolvien, Maurice and Zakharov, Pavel and Zhu, Haodong}, title = {{The Number of Random 2-SAT Solutions Is Asymptotically Log-Normal}}, booktitle = {Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2024)}, pages = {39:1--39:15}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-348-5}, ISSN = {1868-8969}, year = {2024}, volume = {317}, editor = {Kumar, Amit and Ron-Zewi, Noga}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX/RANDOM.2024.39}, URN = {urn:nbn:de:0030-drops-210329}, doi = {10.4230/LIPIcs.APPROX/RANDOM.2024.39}, annote = {Keywords: satisfiability problem, 2-SAT, random satisfiability, central limit theorem} }
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