The cover has been kindly provided by Eric Heller of Harvard University and comes from his Resonance Fine Art Gallery, which provides many illustrations of nonlinear dynamics and its manifestations in quantum mechanics. This particular design shows random superposition of eigenfuctions for a linear ramp potential — a model for more general systems exhibiting some universal patterns of high energy modes. Hence it illustrates some functional and harmonic analysis, dynamical systems, partial differential equations, probability, and mathematical physics.