  Due to its ubiquitous presence, turbulence is often invoked to explain the
origin of nonthermal particles in astrophysical sources of high-energy
emission. With particle-in-cell simulations, we study decaying turbulence in
magnetically-dominated (or equivalently, "relativistic") pair plasmas. We find
that the generation of a power-law particle energy spectrum is a generic
by-product of relativistic turbulence. The power-law slope is harder for higher
magnetizations and stronger turbulence levels. In large systems, the slope
attains an asymptotic, system-size-independent value, while the high-energy
spectral cutoff increases linearly with system size; both the slope and the
cutoff do not depend on the dimensionality of our domain. By following a large
sample of particles, we show that particle injection happens at reconnecting
current sheets; the injected particles are then further accelerated by
stochastic interactions with turbulent fluctuations. Our results have important
implications for the origin of non-thermal particles in high-energy
astrophysical sources.
