Improved Bounds for Fully Dynamic Matching via Ordered Ruzsa-Szemer\'edi Graphs
<|reference_start|>Improved Bounds for Fully Dynamic Matching via Ordered Ruzsa-Szemer\'edi Graphs: In a very recent breakthrough, Behnezhad and Ghafari [arXiv'24] developed a novel fully dynamic randomized algorithm for maintaining a $(1-\epsilon)$-approximation of maximum matching with amortized update time potentially much better than the trivial $O(n)$ update time. The runtime of the BG algorithm is parameterized via the following graph theoretical concept:   * For any $n$, define $ORS(n)$ -- standing for Ordered RS Graph -- to be the largest number of edge-disjoint matchings $M_1,\ldots,M_t$ of size $\Theta(n)$ in an $n$-vertex graph such that for every $i \in [t]$, $M_i$ is an induced matching in the subgraph $M_{i} \cup M_{i+1} \cup \ldots \cup M_t$.   Then, for any fixed $\epsilon > 0$, the BG algorithm runs in \[   O\left( \sqrt{n^{1+O(\epsilon)} \cdot ORS(n)} \right) \] amortized update time with high probability, even against an adaptive adversary. $ORS(n)$ is a close variant of a more well-known quantity regarding RS graphs (which require every matching to be induced regardless of the ordering). It is currently only known that $n^{o(1)} \leqslant ORS(n) \leqslant n^{1-o(1)}$, and closing this gap appears to be a notoriously challenging problem.   In this work, we further strengthen the result of Behnezhad and Ghafari and push it to limit to obtain a randomized algorithm with amortized update time of \[   n^{o(1)} \cdot ORS(n) \] with high probability, even against an adaptive adversary. In the limit, i.e., if current lower bounds for $ORS(n) = n^{o(1)}$ are almost optimal, our algorithm achieves an $n^{o(1)}$ update time for $(1-\epsilon)$-approximation of maximum matching, almost fully resolving this fundamental question. In its current stage also, this fully reduces the algorithmic problem of designing dynamic matching algorithms to a purely combinatorial problem of upper bounding $ORS(n)$ with no algorithmic considerations.<|reference_end|>
@article{assadi2024improved,
    title={Improved Bounds for Fully Dynamic Matching via Ordered Ruzsa-Szemeredi
  Graphs},
    author={Sepehr Assadi, Sanjeev Khanna, Peter Kiss},
    journal={arXiv preprint arXiv:2406.13573},
    year={2024},
    archivePrefix={arXiv},
    eprint={2406.13573},
    primaryClass={cs.DS}
}