Mapping Class Groups of Simply Connected K\"ahler Manifolds

Abstract

This paper has 3 principal goals: (1) to survey what is know about mapping class and Torelli groups of simply connected compact Kaehler manifolds, (2) supplement these results, and (3) present a list of questions and open problems to stimulate future work. Apart from reviewing general background, the paper focuses on the case of hypersurfaces in projective space. We explain how older results of Carlson--Toledo arXiv:alg-geom/9708002 and recent results of Kreck--Su arXiv:2009.08054 imply that the homomorphism from the fundamental group of the moduli space of hypersurfaces in P^4 to the mapping class group of the underlying manifold has a very large kernel (contains a free group of rank 2) and has image of infinite index. This is in contrast to the case of curves, where the homomorphism is an isomorphism.