  Using 2.5-dimensional Particle-in-Cell simulations, we study the kinetic
physics of relativistic shear flow boundary in collisionless electron-positron
(e+e-) plasmas. We find efficient magnetic field generation and particle
energization at the shear boundary, driven by streaming instabilities across
the shear interface and sustained by the shear flow. Nonthermal, anisotropic
high-energy particles are accelerated across field lines to produce a power-law
tail, truncated at energies below the shear Lorentz factor. These results have
important implications for the dissipation and radiation of jets in blazars,
gamma-ray bursts and other relativistic outflows.
