Applying integral relations to improve ab initio structure and reaction calculations for light nuclei

The variational Monte Carlo and Green's function Monte Carlo methods, which use random sampling in position space instead of basis expansions, have had great success in computing energy levels and transition probabilities in light nuclei. However, they can be difficult to apply where "long-range" wave function properties like scattering amplitudes and the large-radius tails of bound states are important. The customary variational trial functions are ill-suited to describing the clustering properties that can dominate at long range, and effective Monte Carlo sampling schemes for the low-probability tails and "off-diagonal" quantities are hard to identify. We will describe calculations that mitigate these difficulties by avoiding direct calculation of long-range amplitudes in the wave function and instead finding them from integrals over better-computed short-range parts of the wave function. Applications presented will include spectroscopic overlaps for one-nucleon and alpha-particle removal, true scattering calculations in A = 4,5 systems, and resonant scattering at A = 5 using pseudo-bound variational wave functions.