Abstract
It is well known that two structures \({\cal A}\) and \({\cal B}\) are indistinguishable by sentences of the infinitary logic with k variables \(L^k_{\infty\omega}\) iff Duplicator wins the Barwise game on \({\cal A}\) and \({\cal B}\) with k pebbles. The complexity of the problem who wins the game is in general unknown if k is a part of the input. We prove that the problem is in PTIME for some special classes of structures such as finite directed trees and infinite regular trees. More specifically, we show an algorithm running in time log (k) ( |A| + |B| )O(1).
The algorithm for regular trees is based on a characterization of the winning pairs \(({\cal A}, {\cal B})\) which is valid also for a more general case of (potentially infinite) rooted trees.
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References
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© 2003 Springer-Verlag Berlin Heidelberg
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Krzeszczakowski, Ć. (2003). Pebble Games on Trees. In: Baaz, M., Makowsky, J.A. (eds) Computer Science Logic. CSL 2003. Lecture Notes in Computer Science, vol 2803. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-45220-1_29
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DOI: https://doi.org/10.1007/978-3-540-45220-1_29
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-40801-7
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