ZERO AND ONE-DIMENSIONAL PROBES WITH N=8 SUPERSYMMETRY

We study the symmetry structure of N = 8 quantum mechanics, and apply it to the physics of D0-brane probes in type I' string theory. We focu s on the theory with a global Spin(8) R symmetry which arises upon dim ensional reduction from 2d field theory with (0,8) supersymmetry. Ther e are several puzzles involving supersymmetry which we resolve. In par ticular, by taking into account the gauge constraint and central charg e we explain how the system preserves supersymmetry despite having dif ferent numbers of bosonic and fermionic variables. The resulting zero- point energy leads to a Linear potential consistent with supersymmetry , and the metric is largely unconstrained. We discuss implications for type I' string theory and the matrix model proposal for M theory. (C) 1997 Elsevier Science B.V.