Light bullet in parity-time symmetric potential

We derive light bullet solution of a (3+1)-dimensional nonlinear Schrödinger equation with inhomogeneous diffraction/dispersion and nonlinearity in presence of the parity-time symmetric potential. All characteristic parameters such as amplitude, width, and phase of solution are adapted to the diffraction/dispersion variation. The broadening and compression of LB are studied in the exponential diffraction/dispersion-decreasing medium and the periodic-modulated system. Moreover, the phase changes of light bullet in two kinds of systems are also illustrated.