  We compute L2-invariants of certain nonuniform lattices in semisimple Lie
groups by means of the Borel-Serre compactification of arithmetically defined
locally symmetric spaces. The main results give new estimates for
Novikov-Shubin numbers and vanishing L2-torsion for lattices in groups with
even deficiency. We discuss applications to Gromov's Zero-in-the-Spectrum
Conjecture as well as to a proportionality conjecture for the L2-torsion of
measure equivalent groups.
