We define new graph parameters that generalize tree-width, degeneracy, and generalized coloring numbers for sparse graphs, and clique-width and twin-width for dense graphs. Those parameters are defined using variants of the Cops and Robber game, in which the robber has speed bounded by a fixed constant $r\in\mathbb N\cup\{\infty\}$, and the cops perform flips (or perturbations) of the considered graph. We propose a new notion of tameness of a graph class, called bounded flip-width, which is a dense counterpart of classes of bounded expansion of Ne\v{s}et\v{r}il and Ossona de Mendez, and includes classes of bounded twin-width of Bonnet, Kim, Thomass\'e and Watrigant. We prove that boundedness of flip-width is preserved by first-order interpretations, or transductions, generalizing previous results concerning classes of bounded expansion and bounded twin-width. We provide an algorithm approximating the flip-width of a given graph, which runs in slicewise polynomial time (XP) in the size of the graph. We also propose a more general notion of tameness, called almost bounded flip-width, which is a dense counterpart of nowhere dense classes, and includes all structurally nowhere dense classes. We conjecture, and provide evidence, that classes with almost bounded flip-width coincide with monadically dependent classes, introduced by Shelah in model theory.
翻译:摘要:我们定义了新的图参数,这些参数概括了稀疏图的树宽、退化度和广义染色数,以及稠密图的团宽与孪生宽。这些参数通过警察与强盗游戏的变体定义,其中强盗的速度由固定常数 $r\in\mathbb N\cup\{\infty\}$ 限制,而警察对目标图执行翻转(或扰动)操作。我们提出了一种新的图类驯服性概念,称为有界翻转宽度,这是 Nešetřil 和 Ossona de Mendez 提出的有界扩张类的稠密对应,并包含 Bonnet、Kim、Thomassé 和 Watrigant 提出的有界孪生宽类。我们证明翻转宽度的有界性在一阶解释(或转导)下保持不变,这推广了关于有界扩张类与有界孪生宽类的既有结论。我们提出了一种近似给定图翻转宽度的算法,该算法在图的规模上运行于切片多项式时间(XP)内。此外,我们提出了更一般的驯服性概念——几乎有界翻转宽度,这是无处稠密类的稠密对应,并包含所有结构无处稠密类。我们推测(并提供证据)几乎有界翻转宽度类与 Shelah 在模型论中引入的单演依赖类一致。