Non-relativistic expansion of Dirac equation with spherical scalar and vector potentials by similarity renormalization group

By following the conventional similarity renormalization group (SRG) expansion of the Dirac equation developed in [J.-Y. Guo, Phys. Rev. C $\mathbf{\text{85}}$, 021302 (2012)], we work out the analytic expression of the $1\mathrm{/}{M}^4$ order and verify the convergence of this method. As a step further, the reconstituted SRG method is proposed by using the re-summation technique. The speed of convergence of the reconstituted SRG becomes much faster than the conventional one, and the single-particle densities with the reconstituted SRG are also almost identical to the exact values.