• Bulletin of the Korean Mathematical Society
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• v.52 no.4
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• pp.1077-1095
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• 2015

In this paper we study equivariant crossed modules in its link with strict graded categorical groups. The resulting Schreier theory for equivariant group extensions of the type of an equivariant crossed module generalizes both the theory of group extensions of the type of a crossed module and the one of equivariant group extensions.

• Journal of the Korean Mathematical Society
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• v.35 no.4
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• pp.891-901
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• 1998

We give a definition of the vector-valued index for Z-actions extending the numerical index in [9] and prove the extension theorem for Z-actions for showing basic properties of the vector-valued index.