Kodai Mathematical Journal
- Kodai Math. J.
- Volume 28, Number 1 (2005), 131-145.
Global lightlike manifolds and harmonicity
A new class of semi-Riemannian and lightlike manifolds (including globally null) is constructed by using a hypersurface of an orientable Riemannian manifold, endowed with the second fundamental form instead of a metric induced from the ambient space. We show the existence (or non-existence) of harmonic tensor fields and harmonic maps and extend to the semi-Riemannian and lightlike case a result of Chen-Nagano . Then we deal with general lightlike submanifolds immersed in a semi-Riemannian manifold and propose a definition of minimal lightlike submanifolds, which generalize the one given in  in the Minkowski space . Several examples are given throughout.
Kodai Math. J. Volume 28, Number 1 (2005), 131-145.
First available in Project Euclid: 23 March 2005
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Bejan, C. L.; Duggal, K. L. Global lightlike manifolds and harmonicity. Kodai Math. J. 28 (2005), no. 1, 131--145. doi:10.2996/kmj/1111588042. https://projecteuclid.org/euclid.kmj/1111588042