• Communications of the Korean Mathematical Society
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• v.11 no.1
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• pp.209-214
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• 1996

A flat space is characterized by tube volumes about geodesic balls. Similar characterizations are also given for other rank one symmetric spaces.

• Journal of the Korean Mathematical Society
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• v.48 no.1
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• pp.83-104
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• 2011

In this note, compound-commuting additive maps on matrix spaces are studied. We show that compound-commuting additive maps send rank one matrices to matrices of rank less than or equal to one. By using the structural results of rank-one nonincreasing additive maps, we characterize compound-commuting additive maps on four types of matrices: triangular matrices, square matrices, symmetric matrices and Hermitian matrices.

• Communications of the Korean Mathematical Society
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• v.21 no.1
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• pp.151-163
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• 2006

Any simply connected fixed point cohomogeneity one riemannian manifold with positive sectional curvature is diffeomorphic to one of the compact rank one symmetric spaces.