Relativistic particle in a three-dimensional box
  We generalize the work of Alberto, Fiolhais and Gil and solve the problem of a Dirac particle confined in a 3-dimensional box. The non-relativistic and ultra-relativistic limits are considered and it is shown that the size of the box determines how relativistic the low-lying states are. The consequences for the density of states of a relativistic fermion gas are briefly discussed. 
Pedro Alberto, Saurya Das, Elias C. Vagenas
quant-ph cond-mat.quant-gas gr-qc hep-th physics.atom-ph