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Deformation of Schottky groups in complex hyperbolic space

Beat Aebischergif - Robert R. Minergif

Abstract:

Let G=PU(1,d) be the group of holomorphic isometries of complex hyperbolic space tex2html_wrap_inline949 . The latter is a Kähler manifold with constant negative holomorphic sectional curvature. We call a finitely generated discrete group tex2html_wrap_inline951 a Schottky group of rank n if the sides of its Dirichlet domain (with respect to some point) are disjoint and not asymptotic. We consider smooth families of such groups tex2html_wrap_inline955 with tex2html_wrap_inline957 depending smoothly ( tex2html_wrap_inline959 ) on tex2html_wrap_inline961 . The groups tex2html_wrap_inline963 are all algebraically isomorphic to the free group in n generators, i.e. there are canonical isomorphisms tex2html_wrap_inline967 . We shall construct a homeomorphism tex2html_wrap_inline969 of tex2html_wrap_inline971 which is equivariant with respect to these groups:

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which is quasiconformal on tex2html_wrap_inline973 with respect to the Heisenberg metric, and which is symplectic in the interior. As a corollary, the limit sets of Schottky groups of equal rank are quasiconformally equivalent to each other.

The main tool for the construction is a time-dependent Hamiltonian vector field used to define a diffeomorphism, mapping tex2html_wrap_inline975 onto tex2html_wrap_inline977 , where tex2html_wrap_inline977 is the Dirichlet domain of tex2html_wrap_inline963 . In two steps, this is extended equivariantly to tex2html_wrap_inline983 .

The method yields similar results for real hyperbolic space, while the analog for the other rank-one symmetric spaces of noncompact type cannot hold.





Robert Miner
Wed Jan 22 10:50:29 CST 1997