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On the number of types in sparse graphs
TLDR
It is proved that for every class of graphs ℒ which is nowhere dense, and for every first order formula φ(x, y), the number of subsets of A|y| which are of the form ū for some valuation ū of x in G is bounded by O(|A||x|ε), which provides optimal bounds on the VC-density of first-order definable set systems in nowhere dense graph classes.Abstract:
We prove that for every class of graphs $\mathcal{C}$ which is nowhere dense, as defined by Nesetril and Ossona de Mendez, and for every first order formula $\phi(\bar x,\bar y)$, whenever one draws a graph $G\in \mathcal{C}$ and a subset of its nodes $A$, the number of subsets of $A^{|\bar y|}$ which are of the form $\{\bar v\in A^{|\bar y|}\, \colon\, G\models\phi(\bar u,\bar v)\}$ for some valuation $\bar u$ of $\bar x$ in $G$ is bounded by $\mathcal{O}(|A|^{|\bar x|+\epsilon})$, for every $\epsilon>0$. This provides optimal bounds on the VC-density of first-order definable set systems in nowhere dense graph classes.
We also give two new proofs of upper bounds on quantities in nowhere dense classes which are relevant for their logical treatment. Firstly, we provide a new proof of the fact that nowhere dense classes are uniformly quasi-wide, implying explicit, polynomial upper bounds on the functions relating the two notions. Secondly, we give a new combinatorial proof of the result of Adler and Adler stating that every nowhere dense class of graphs is stable. In contrast to the previous proofs of the above results, our proofs are completely finitistic and constructive, and yield explicit and computable upper bounds on quantities related to uniform quasi-wideness (margins) and stability (ladder indices).read more
Citations
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Proceedings ArticleDOI
Lossy Kernels for Connected Dominating Set on Sparse Graphs
TL;DR: It is shown that even though the kernelization complexity ofDominating Set and Connected Dominating Set diverges on sparse graphs this divergence is not as extreme as kernelization lower bounds suggest.
Posted Content
Progressive Algorithms for Domination and Independence
TL;DR: In this paper, a generic algorithm called progressive exploration is proposed to develop simple and efficient parameterized graph algorithms for dominating set and distance-r independent set problems, which can be used to give a linear-time fixed-parameter algorithm on any nowhere dense class.
Proceedings ArticleDOI
On the number of types in sparse graphs
TL;DR: In this article, it was shown that the VC-density of first-order definable set systems in nowhere dense graphs can be computed in polynomial time for any valuation u of x in a graph G ∈ l and a subset of its nodes A, for every e > 0.
Journal ArticleDOI
Classes of graphs with low complexity: the case of classes with bounded linear rankwidth
TL;DR: In this article, structural and model theoretic properties of classes with bounded linear rankwidth were studied from the point of view of structural graph theory and finite model theory, respectively, and it was shown that the number of unlabeled graphs of order n with linear rank-width at most r is linearly χ -bounded.
Book ChapterDOI
Linear rankwidth meets stability
TL;DR: In this paper, the structural and model theoretic properties of graph classes with bounded linear rankwidth were studied from the point of view of structural graph theory and finite model theory, respectively.
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