Temporal Reachability Minimization: Delaying vs. Deleting

Authors Hendrik Molter , Malte Renken , Philipp Zschoche

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Author Details

Hendrik Molter
  • Department of Industrial Engineering and Management, Ben-Gurion University of the Negev, Beer Sheva, Israel
  • Faculty IV, Algorithmics and Computational Complexity, Technische Universität Berlin, Germany
Malte Renken
  • Faculty IV, Algorithmics and Computational Complexity, Technische Universität Berlin, Germany
Philipp Zschoche
  • Faculty IV, Algorithmics and Computational Complexity, Technische Universität Berlin, Germany


This work was initiated at the research retreat of the Algorithmics and Computational Complexity group of TU Berlin in September 2020 in Zinnowitz.

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Hendrik Molter, Malte Renken, and Philipp Zschoche. Temporal Reachability Minimization: Delaying vs. Deleting. In 46th International Symposium on Mathematical Foundations of Computer Science (MFCS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 202, pp. 76:1-76:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


We study spreading processes in temporal graphs, i. e., graphs whose connections change over time. These processes naturally model real-world phenomena such as infectious diseases or information flows. More precisely, we investigate how such a spreading process, emerging from a given set of sources, can be contained to a small part of the graph. To this end we consider two ways of modifying the graph, which are (1) deleting connections and (2) delaying connections. We show a close relationship between the two associated problems and give a polynomial time algorithm when the graph has tree structure. For the general version, we consider parameterization by the number of vertices to which the spread is contained. Surprisingly, we prove W[1]-hardness for the deletion variant but fixed-parameter tractability for the delaying variant.

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Graph algorithms
  • Mathematics of computing → Paths and connectivity problems
  • Mathematics of computing → Network flows
  • Temporal Graphs
  • Temporal Paths
  • Disease Spreading
  • Network Flows
  • Parameterized Algorithms
  • NP-hard Problems


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