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The zero forcing numbers and propagation times of gear graphs and helm graphs

Sara Anderton, Rilee Burden, McKenzie Fontenot, Noah Fredrickson, Alexandria Kwon, Sydney Le, Kanno Mizozoe, Erin Raign, August Sangalli, Houston Schuerger and Andrew Schwartz

Vol. 19 (2026), No. 2, 275–296
Abstract

Zero forcing is a dynamic coloring process on graphs. Initially, each vertex of a graph is assigned a color of either blue or white, and then a process begins by which blue vertices force white vertices to become blue. The zero forcing number is the cardinality of the smallest set of initially blue vertices which can force the entire graph to become blue, and the propagation time is the minimum number of steps in such a zero forcing process. In this paper, we determine the zero forcing numbers and propagation times of two infinite classes of graphs called gear graphs and helm graphs.

Keywords
graph classes, zero forcing, propagation time, relaxed chronology, chain set
Mathematical Subject Classification
Primary: 05C50, 05C57, 05C69
Milestones
Received: 14 April 2024
Revised: 9 September 2024
Accepted: 17 September 2024
Published: 8 March 2026

Communicated by Ann N. Trenk
Authors
Sara Anderton
Department of Mathematics
Southeast Missouri State University
Cape Girardeau, MO
United States
Rilee Burden
Department of Mathematics
University of North Texas
Denton, TX
United States
McKenzie Fontenot
Department of Mathematics
University of North Texas
Denton, TX
United States
Noah Fredrickson
Flower Mound, TX
United States
Alexandria Kwon
Little Elm, TX
United States
Sydney Le
Department of Electrical and Computer Engineering
Rice University
Flower Mound, TX
United States
Kanno Mizozoe
Department of Mathematics
Trinity College
Hartford, CT
United States
Erin Raign
Department of Mathematics
University of North Texas
Denton, TX
United States
August Sangalli
Department of Mathematics
University of Denver
Denver, CO
United States
Houston Schuerger
Department of Mathematics
Tarleton State University
Stephenville, TX
United States
Andrew Schwartz
Department of Mathematics
Southeast Missouri State University
Cape Girardeau, MO
United States