We study the effects of Lorentz invariance on relativistic constituent quark model wave functions. The model nucleon wave function of Gross et al. (nucl-th/0606029) is constructed such that there is no orbital angular momentum and that the spin-dependent density is spherical. This model wave function is claimed to be manifestly covariant. We consider two possible interpretations of the nucleon wave function in an arbitrary reference frame. In the first, the seeming covariance of the matrix elements of the electromagnetic current arises from using the Breit frame. Matrix elements have a different appearance in any other frame. In the second interpretation, the electromagnetic current is covariant yet it is not consistent with the general structure required by QFT (e.g., the wave function of the incoming nucleon depends on the momentum of the outgoing nucleon and vice versa).

• Received 8 January 2007

DOI:https://doi.org/10.1103/PhysRevC.76.025203