Nonrelativistic limit of Dirac theory from effective field theory

In this work we analyze the low energy nonrelativistic limit of Dirac theory in the framework of effective field theory. By integrating out the high energy modes of Dirac field, given in terms of a combination of the two-components Weyl spinors, we obtain a low energy effective action for the remaining components, whose equation of motion can then be compared to the Pauli-Schr\"odinger equation after demanding normalization of the wave function. We then discuss the relevance of the terms in the effective action in the context of an anisotropic dimensional analysis which is suitable for nonrelativistic theories.
Comment: 20 pages, typos corrected, minor improvements, references added