Cold-dark-matter cosmology with non-Gaussian fluctuations from inflation

Non-Gaussian primordial fluctuations for structure formation may be generated during the inflationary epoch from the nonlinear interaction of two scalar fields with gravity. Semianalytical stochastic inflation calculations are described for nonlinear long-wavelength evolution in 3+1 dimensions. Long-wavelength fields are governed by a single equation, the separated Hamilton-Jacobi equation. Typically, non-Gaussian fluctuations arise when the scalar fields pass over a sharp feature in their potential surface. The subsequent evolution of these primordial fluctuations are calculated as scales reenter the horizon during the radiation-dominated and matter-dominated eras of the cold-dark-matter scenario. Contour maps for the linear density perturbation as well as the gravitational potential are displayed at the present epoch. In qualitative agreement with observations, one can construct models with enhanced sheetlike structures on the scale of ~25h^-1 Mpc. The cleanest test of non-Gaussian fluctuations will hopefully occur in the near future from large-angle microwave-background anisotropy experiments.