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In recent years, knapsack problems for (in general non-commutative) groups have attracted attention. In this paper, the knapsack problem for wreath products is studied. It turns out that decidability of knapsack is not preserved under wreath product. On the other hand, the class of knapsack-semilinear groups, where solutions sets of knapsack equations are effectively semilinear, is closed under wreath product. As a consequence, we obtain the decidability of knapsack for free solvable groups. Finally, it is shown that for every non-trivial abelian group G, knapsack (as well as the related subset sum problem) for the wreath product G \wr Z is NP-complete.
@InProceedings{ganardi_et_al:LIPIcs.STACS.2018.32,
author = {Ganardi, Moses and K\"{o}nig, Daniel and Lohrey, Markus and Zetzsche, Georg},
title = {{Knapsack Problems for Wreath Products}},
booktitle = {35th Symposium on Theoretical Aspects of Computer Science (STACS 2018)},
pages = {32:1--32:13},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-062-0},
ISSN = {1868-8969},
year = {2018},
volume = {96},
editor = {Niedermeier, Rolf and Vall\'{e}e, Brigitte},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2018.32},
URN = {urn:nbn:de:0030-drops-85201},
doi = {10.4230/LIPIcs.STACS.2018.32},
annote = {Keywords: knapsack, wreath products, decision problems in group theory}
}
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