String Theory Modifies Quantum Mechanics

We argue that the light particles in string theory obey an effective quantum mechanics modified by the inclusion of a quantum-gravitational friction term, induced by unavoidable couplings to unobserved massive string states in the space-time foam. This term is related to the W -symmetries that couple light particles to massive solitonic string states in black hole backgrounds, and has a formal similarity to simple models of environmental quantum friction. It increases apparent entropy, and may induce the wave functions of macroscopic systems to collapse. CERN-TH.6595/92 ACT-17/92 CTP-TAMU-58/92 July 1992 † Permanent address : Center for Theoretical Physics, Dept. of Physics, Texas A & M University, College Station, TX 77843-4242, USA, and Astroparticle Physics Group, Houston Advanced Research Center (HARC), The Woodlands, TX 77381, USA.