E. Leuzinger et C. Pittet, ISOPERIMETRIC-INEQUALITIES FOR LATTICES IN SEMISIMPLE LIE-GROUPS OF RANK-2, Geometric and functional analysis, 6(3), 1996, pp. 489-511
Let G be a connected semisimple Lie group with finite center. Let Gamm
a be an irreducible non-uniform lattice in G. We show that if the real
rank of G is 2 then the Dehn (or filling) function of Gamma is expone
ntial.