Cosmic strings from pseudo-anomalous Fayet-Iliopoulos U(1) in D3/D7 brane inflation

TL;DR

This paper explores how pseudo-anomalous U(1) gauge symmetries in D3/D7 brane inflation models lead to local cosmic strings with unique properties, affecting inflation dynamics and cosmological implications.

Contribution

It demonstrates that FI terms in D3/D7 inflation are field-dependent and linked to pseudo-anomalous U(1)s, resulting in local cosmic strings with currents, a novel insight in string cosmology.

Findings

FI terms are field-dependent, not constant, in supergravity.

Cosmic strings from pseudo-anomalous U(1)s are local and can support currents.

The scale of inflation is set by the Green-Schwarz parameter.

Abstract

We examine the consequences of recent developments on Fayet-Iliopoulos (FI) terms for D-term inflationary models. There is currently no known way to couple constant FI terms to supergravity consistently; only field-dependent FI terms are allowed. These are natural in string theory and we argue that the FI term in D3/D7 inflation turns out to be of this type, corresponding to a pseudo-anomalous U(1). T he anomaly is canceled by the Green-Schwarz mechanism in 4 dimensions. Inflation proceeds as usual, except that the scale is set by the GS parameter. Cosmic strings resulting from a pseudo-anomalous U(1) have potentially interesting characteristics. Originally expected to be global, they turn out to be local in the string theory context and can support currents. We outline the nature of these strings, discuss bounds on their formation, and summarize resulting cosmological consequences.