Anomaly-Induced Gauge Unification and Brane/Bulk Couplings in Gravity-Localized Theories

TL;DR

This paper explores how anomaly-induced effects in gravity-localized compactifications can naturally lead to gauge coupling unification, but also discusses significant phenomenological challenges and potential resolutions.

Contribution

It demonstrates that gauge coupling unification can arise from anomalies in gravity-localized theories and analyzes associated phenomenological issues.

Findings

Gauge unification occurs naturally via anomalies in these models.

Phenomenological difficulties include incompatibility of GUT and electroweak scales.

Brane/bulk couplings are generally too small for observable effects.

Abstract

It has recently been proposed that gravity-localized compactifications can generate the required gauge hierarchy without the need for hierarchically large extra spacetime dimensions. In this paper, we show that gauge coupling unification arises naturally in such scenarios as a result of the anomaly induced by the rescaling of the wavefunctions of the brane fields. Thus, ``anomaly-induced'' gauge coupling unification can easily explain the apparent low-energy gauge couplings in gravity-localized compactifications. However, we also point out a number of phenomenological difficulties with such compactifications, including an inability to accommodate the GUT scale and the electroweak scale simultaneously. We also show that brane/bulk couplings in this scenario are generically too small to be phenomenologically relevant. Finally, we speculate on possible resolutions to these puzzles.