Abstract
A graph G is called a pseudo-core if every endomorphism of G is either an automorphism or a colouring. An interesting problem in graph theory is to distinguish whether a graph is a core. The twisted Grassmann graphs, constructed by van Dam and Koolen in (Invent Math 162:189–193, 2005), are the first known family of non-vertex-transitive distance-regular graphs with unbounded diameter. In this paper, we show that every twisted Grassmann graph is a pseudo-core.
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Acknowledgments
The authors are thankful to the anonymous reviewers for many helpful suggestions and great improvements in proofs. This research was supported by National Natural Science Foundation of China (Projects 11371072, 11301270, 11271047, 11371204, 11501036, 11671043), the Fundamental Research Funds for the Central University of China, and Youth Scholar Program of Beijing Normal University and China Postdoctoral Science Foundation (2015M570958).
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Supported by NSFC (Projects 11371072, 11301270, 11271047, 11371204, 11501036, 11671043), the Fundamental Research Funds for the Central University of China, and Youth Scholar Program of Beijing Normal University and China Postdoctoral Science Foundation (2015M570958).
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Lv, B., Huang, LP. & Wang, K. Endomorphisms of Twisted Grassmann Graphs. Graphs and Combinatorics 33, 157–169 (2017). https://doi.org/10.1007/s00373-016-1738-3
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DOI: https://doi.org/10.1007/s00373-016-1738-3