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What and Who

Counting Small Induced Subgraphs Satisfying Monotone Properties

Marc Roth
Merton College, University of Oxford
AG1 Mittagsseminar (own work)
AG 1  
AG Audience
English

Date, Time and Location

Thursday, 10 September 2020
13:00
30 Minutes
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Abstract

Given a graph property P, the problem #IndSub(P) asks, on input a graph G and a positive integer k, to compute the number of induced subgraphs of size k in G that satisfy P. The search for explicit criteria on P ensuring that #IndSub(P) is hard was initiated by Jerrum and Meeks [J. Comput. Syst. Sci. 15] and is part of the major line of research on counting small patterns in graphs. However, apart from an implicit result due to Curticapean, Dell and Marx [STOC 17] proving that a full classication into "easy" and "hard" properties is possible and some partial results on edge-monotone properties due to Meeks [Discret. Appl. Math. 16] and Dörfler et al. [MFCS 19], not much is known.


In this work, we fully answer and explicitly classify the case of monotone, that is subgraph-closed, properties: We show that for any non-trivial monotone property P, the problem #IndSub(P) cannot be solved in time f(k) * |V(G)|^o(k/sqrt(log k)) for any function f, unless the Exponential Time Hypothesis fails. By this, we establish that any signicant improvement over the brute-force approach is unlikely; in the language of parameterized complexity, we also obtain a #W[1]-completeness result.

The methods we develop for the above problem also allow us to prove a conjecture by Jerrum and Meeks [TOCT 15, Combinatorica 19]: #IndSub(P) is #W[1]-complete if P is a non-trivial graph property only depending on the number of edges of the graph.


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Philip Wellnitz
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Philip Wellnitz, 09/09/2020 13:56
Philip Wellnitz, 09/09/2020 13:43 -- Created document.