Dirac equation with a magnetic field in 3D non-commutative phase space

For a spin-1/2 particle moving in a background magnetic field in noncommutative phase space, the Dirac equation is solved when the particle is allowed to move off the plane that the magnetic field is perpendicular to. It is shown that the motion of the charged particle along the magnetic field has the effect of increasing the magnetic field. In the classical limit, matrix elements of the velocity operator related to the probability give a clear physical picture. Along an effective magnetic field, the mechanical momentum is conserved and the motion perpendicular to the effective magnetic field follows a round orbit. If using the velocity operator defined by the coordinate operators, the motion becomes complicated.     

纳米级BaAl2O4微粉的制备和性质

分别用溶胶－凝胶法和低温固相反应法制得了纳米级BaAl2O4微粉，用电镜观察了其形貌和粒径的大小，用X－射线衍射仪进行了物相分析，测定了纯度与晶型，讨论了制备方法与粒度大小的相互关系。