The first year Wilkinson Microwave Anisotropy Probe data favors primordial adiabatic fluctuation with a running spectral index with n _ { s } > 1 on a large scale and n _ { s } < 1 on a smaller scale .
The model building of inflation that predicts perturbations with such a spectrum is a challenge , because most models predict fluctuations with either n _ { s } > 1 ( hybrid inflation ) or n _ { s } < 1 ( new , chaotic , or topological inflation ) .
We give a sensible particle physics model in supergravity that accommodates the desired running of the spectral index using double inflation .