D-term inflation after spontaneous symmetry breaking

We show that one-loop quantum corrections to the potential energy density in supersymmetric hybrid inflation, outside the inflationary valley, cannot be neglected. A method is presented to calculate these one-loop corrections and they are applied to the case of D-term hybrid inflation, where a significant amount of inflation is shown to occur after spontaneous symmetry breaking. Taking this into account improves the agreement with WMAP measurements. A gauge coupling of up to 0.3 is still consistent with the CMB density perturbation. The spectral index is predicted in between 0.98 and 1.00 and the cosmic string contribution to the CMB anisotropy is sufficiently reduced.