,
Martin Zimmermann
Creative Commons Attribution 4.0 International license
We determine the complexity of second-order HyperLTL satisfiability, finite-state satisfiability, and model-checking: All three are equivalent to truth in third-order arithmetic. We also consider two fragments of second-order HyperLTL that have been introduced with the aim to facilitate effective model-checking by restricting the sets one can quantify over. The first one restricts second-order quantification to smallest/largest sets that satisfy a guard while the second one restricts second-order quantification further to least fixed points of (first-order) HyperLTL definable functions. All three problems for the first fragment are still equivalent to truth in third-order arithmetic while satisfiability for the second fragment is Σ₁¹-complete, i.e., only as hard as for (first-order) HyperLTL and therefore much less complex. Finally, finite-state satisfiability and model-checking are in Σ₂² and are Σ₁¹-hard, and thus also less complex than for full second-order HyperLTL.
@InProceedings{frenkel_et_al:LIPIcs.CSL.2025.10,
author = {Frenkel, Hadar and Zimmermann, Martin},
title = {{The Complexity of Second-Order HyperLTL}},
booktitle = {33rd EACSL Annual Conference on Computer Science Logic (CSL 2025)},
pages = {10:1--10:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-362-1},
ISSN = {1868-8969},
year = {2025},
volume = {326},
editor = {Endrullis, J\"{o}rg and Schmitz, Sylvain},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2025.10},
URN = {urn:nbn:de:0030-drops-227679},
doi = {10.4230/LIPIcs.CSL.2025.10},
annote = {Keywords: HyperLTL, Satisfiability, Model-checking}
}