Abstract
An additive functional of a rooted tree is a functional that can be calculated recursively as the sum of the values of the functional over the branches, plus a certain toll function. Svante Janson recently proved a central limit theorem for additive functionals of conditioned Galton–Watson trees under the assumption that the toll function is local, i.e. only depends on a fixed neighbourhood of the root. We extend his result to functionals that are “almost local” in a certain sense, thus covering a wider range of functionals. The notion of almost local functional intuitively means that the toll function can be approximated well by considering only a neighbourhood of the root. Our main result is illustrated by several explicit examples including natural graph-theoretic parameters such as the number of independent sets, the number of matchings, and the number of dominating sets. We also cover a functional stemming from a tree reduction procedure that was studied by Hackl, Heuberger, Kropf, and Prodinger.
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Acknowledgements
We thank Jim Fill for useful remarks and the anonymous referees for very detailed reports and helpful comments which helped to improve the exposition.
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The first author was partially supported by the Division for Research Development (DRD) of Stellenbosch University. The second author was supported by the Czech Science Foundation, Grant Number GJ16-07822Y, with institutional support RVO:67985807. The third author was supported by the National Research Foundation of South Africa, Grant 96236. An extended abstract of this paper appeared in the Proceedings of the 29th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms, AofA 2018, see [15].
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Ralaivaosaona, D., Šileikis, M. & Wagner, S. A Central Limit Theorem for Almost Local Additive Tree Functionals. Algorithmica 82, 642–679 (2020). https://doi.org/10.1007/s00453-019-00622-4
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DOI: https://doi.org/10.1007/s00453-019-00622-4