On Quantum Unique Ergodicity for Locally Symmetric Spaces

We construct an equivariant microlocal lift for locally symmetric spaces. In other words, we demonstrate how to lift, in a semi-canonical fashion, limits of eigenfunction measures on locally symmetric spaces to Cartan-invariant measures on an appropriate bundle. The construction uses elementary features of the representation theory of semisimple real Lie groups, and can be considered a generalization of Zelditch’s results from the upper half-plane to all locally symmetric spaces of noncompact type. This will be applied in a sequel to settle a version of the quantum unique ergodicity problem on certain locally symmetric spaces. The second author was supported in part by NSF Grant DMS-0245606. Part of this work was performed at the Clay Institute Mathematics Summer School in Toronto. Received: September 2005 Revision: August 2006 Accepted: August 2006     

Photoemission with picosecond lasers: fast electron dynamics at theGaAs (110) surface

Subpicosecond pulses of 10.7-eV radiation from a tunable laser-based source are used to carry out photoemission investigations of the electronic dynamics on the laser-excited surface of GaAs (110). Angle-resolved studies have revealed a rapid surface intervalley scattering process that transfers electrons between the directly excited, surface Brillouin zone center to a previously unobserved valley within the bandgap at the surface zone edge. The scattering time has been determined to be 0.4±0.1 ps. A model that describes the scattering dynamics is presented