The orthogonality dimension of a graph over ℝ is the smallest integer d for which one can assign to every vertex a nonzero vector in ℝ^d such that every two adjacent vertices receive orthogonal vectors. For an integer d, the d-Ortho-Dim_ℝ problem asks to decide whether the orthogonality dimension of a given graph over ℝ is at most d. We prove that for every integer d ≥ 3, the d-Ortho-Dim_ℝ problem parameterized by the vertex cover number k admits a kernel with O(k^{d-1}) vertices and bit-size O(k^{d-1} ⋅ log k). We complement this result by a nearly matching lower bound, showing that for any ε > 0, the problem admits no kernel of bit-size O(k^{d-1-ε}) unless NP ⊆ coNP/poly. We further study the kernelizability of orthogonality dimension problems in additional settings, including over general fields and under various structural parameterizations.
@InProceedings{haviv_et_al:LIPIcs.IPEC.2024.8, author = {Haviv, Ishay and Rabinovich, Dror}, title = {{Kernelization for Orthogonality Dimension}}, booktitle = {19th International Symposium on Parameterized and Exact Computation (IPEC 2024)}, pages = {8:1--8:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-353-9}, ISSN = {1868-8969}, year = {2024}, volume = {321}, editor = {Bonnet, \'{E}douard and Rz\k{a}\.{z}ewski, Pawe{\l}}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2024.8}, URN = {urn:nbn:de:0030-drops-222341}, doi = {10.4230/LIPIcs.IPEC.2024.8}, annote = {Keywords: Orthogonality dimension, Fixed-parameter tractability, Kernelization, Graph coloring} }
Feedback for Dagstuhl Publishing