Possibility of controlling the light speed in a Bose condensate by an external static magnetic field

We theoretically study the influence of an external static magnetic field on the slowing of electromagnetic pulses in a Bose-Einstein condensate of hydrogenlike atoms. The description is based on the analysis of the Zeeman splitting of hyperfine levels corresponding to the ground and excited states of alkali-metal atoms. We find the dependencies of the group velocity and absorption rate of the pulses on the intensity of the magnetic field for two-component Bose condensate of sodium atoms. The possibility of controlling the ultraslow light phenomenon in this system by the external static magnetic field is discussed.