D-term inflation without cosmic strings

TL;DR

This work addresses the cosmic-string problem in D-term inflation by extending the minimal model with a second oppositely charged hypermultiplet pair, creating an $N=2$-inspired setup with an FI term and a semilocal string sector. Radiative corrections yield a Coleman–Weinberg-type potential that supports slow-roll inflation with $n\approx0.98$ and $R\lesssim3\times10^{-5}$, and the model predicts a GUT-scale onset of gauge breaking at $S_c\sim10^{16}$ GeV. Post-inflation, the defect sector becomes semilocal with $β=1$, and no string network forms in the Bogomolnyi limit, avoiding CMB constraints from cosmic strings, while remaining consistent with supergravity. The construction connects D-term inflation to string-theoretic settings in type II/CY scenarios, offering a testable link between early-universe cosmology and brane/ CY physics, though details of SUSY breaking and possible textures or vortons remain to be explored.

Abstract

We present a superstring-inspired version of D-term inflation which does not lead to cosmic string formation and appears to satisfy the current CMB constraints. It differs from minimal D-term inflation by a second pair of charged superfields which makes the strings non-topological (semilocal). The strings are also BPS, so the scenario is expected to survive supergravity corrections. The second pair of charged superfields arises naturally in several brane and conifold scenarios, but its effect on cosmic string formation had not been noticed so far.