Modern constraints on F-term SUSY hybrid inflation models
University of Delaware
We study modifications of supersymmetric hybrid inflation, which continues to be one of the most popular inflationary models. The seminal formulation considered the VG+Δ V potential, in which one can show that [special characters ommitted] , which indicates that the breaking scale M ∼ 1016 GeV. This is a non-trivial fact, and provides a clue the group may be a Grand Unified Theory (GUT). Inspired by this, we consider inflating while constraining the breaking scale M at the MSSM gauge coupling unification scale, 2.86 × 1016 GeV. We show that one can inflate successfully; in particular, we use non-minimal Kähler to achieve, for the recent Planck bounds 0.945 < ns < 0.975, r ≈ 3 × 10-4 in the case where V is bounded from below, and r ≈ 1 × 10-2 where this condition is relaxed. Unfortunately, GUTs tend to predict topological defects. To ameliorate this problem, we consider the addition of a Planck-suppressed term which gives rise to shifted inflation, where one inflates in a similar way except that ||[straight phi]|| ≠ 0. We show that one can inflate successfully; one achieves similar results as in the standard case, including the large r solutions particular to non-minimal Kähler contributions. We achieve r ≈ 0.02, which is similar to the non-minimal standard case. Finally, we consider a generalization of the model to include Planck-suppressed R-symmetry violation, parametrized by α. One can generate masses more naturally in MSSM by treating R-symmetry as approximate, and we discover that, keeping to the standard inflationary track ||[straight phi]|| = 0, the effect is to raise r in the preferred ns range by about four orders of magnitude as compared with the standard case, for α ≈ 10-9 . By considering α ≈ 10-7 , one can achieve r ≈ 10 -4 . This is fairly remarkable in that it is done with only minimal Kähler.