A research on the geometric singularities of non-linear phenomena

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In this research project we constructed the notion of 'lightlike curvature' for spacelike submanifolds of Lorentzian space forms by using the notion of 'lightcone Gauss maps'.As an application of the theory of Legendrian singularities, we described the singularities of the lighhtlike hypersurface along a spacelike submanifold. Moreover, we constructed a geometric framework to describe the caustics of world sheets which is an important notion in the theory of general relativity and the brane world scenario. We clarified the relation of the caustics and the wave front propagations iby using the theory of graph-like Legendrian unfoldings.