  We present a theoretical study of the processes d(d,p)3H and d(d,n)3He at
energies of interest for energy production and for big-bang nucleosynthesis. We
accurately solve the four body scattering problem using the ab-initio
hyperspherical harmonic method, starting from nuclear Hamiltonians which
include modern two- and three-nucleon interactions, derived in chiral effective
field theory. We report results for the astrophysical factor, the quintet
suppression factor, and various single and double polarized observables. An
estimate of the "theoretical uncertainty" for all these quantities is provided
by varying the cutoff parameter used to regularize the chiral interactions at
high momentum.
