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Hiroshi Nishiyama Last modified date:2020.10.10

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Academic Degree
Doctor (Engineering)
Country of degree conferring institution (Overseas)
Field of Specialization
Graph Algorithms
Total Priod of education and research career in the foreign country
Academic Activities
1. Pavol Hell, Hiroshi Nishiyama, Ladislav Stacho, Hamiltonian cycles in covering graphs of trees, Discrete Applied Mathematics, 2020.08, Hamiltonicity of graphs possessing symmetry has been a popular subject of research, with focus on vertex-transitive graphs, and in particular on Cayley graphs. In this paper, we consider the Hamiltonicity of another class of graphs with symmetry, namely covering graphs of trees. In particular, we study the problem for covering graphs of trees, where the tree is a voltage graph over a cyclic group. Batagelj and Pisanski were first to obtain such a result, in the special case when the voltage assignment is trivial; in that case, the covering graph is simply a Cartesian product of the tree and a cycle. We consider more complex voltage assignments, and extend the results of Batagelj and Pisanski in two different ways; in these cases the covering graphs cannot be expressed as products. We also provide a linear time algorithm to test whether a given assignment satisfies these conditions..
2. Hiroshi Nishiyama, Yusuke Kobayashi, Yukiko Yamauchi, Shuji Kijima, Masafumi Yamashita, The parity Hamiltonian cycle problem, Discrete Mathematics, 3, 341, 606-626, 2018.03, [URL].
1. Hiroshi Nishiyama, Yukiko Yamauchi, Shuji Kijima, Masafumi Yamashita, The parity Hamiltonian cycle problem in directed graphs, 4th International Symposium on Combinatorial Optimization (ISCO 2016), 2016.05.
2. Hiroshi Nishiyama, Ladislav Stacho, Pavol Hell, Hamiltonian cycles in covering graphs of trees, The 11th Annual International Conference on Combinatorial Optimization and Applications (COCOA 2017), 2017.12.