We investigate jet formation in black - hole systems using 3 - D General Relativistic Particle - In - Cell ( GRPIC ) and 3 - D GRMHD simulations . GRPIC simulations , which allow charge separations in a collisionless plasma , do not need to invoke the frozen condition as in GRMHD simulations . 3 - D GRPIC simulations show that jets are launched from Kerr black holes as in 3 - D GRMHD simulations , but jet formation in the two cases may not be identical . Comparative study of black hole systems with GRPIC and GRMHD simulations with the inclusion of radiate transfer will further clarify the mechanisms that drive the evolution of disk - jet systems .