Grand unification and enhanced quantum gravitational effects

TL;DR

This paper explores how large-field grand unified theories can significantly alter the quantum gravity scale and impact coupling unification, potentially preventing unification due to gravitational effects.

Contribution

It demonstrates that gravitational effects in grand unified theories can be larger than two-loop corrections, affecting unification boundary conditions and feasibility.

Findings

Gravitational effects can surpass two-loop renormalization corrections.

These effects can modify the unification scale and boundary conditions.

In some scenarios, gravitational effects can prevent unification altogether.

Abstract

In grand unified theories with large numbers of fields, renormalization effects significantly modify the scale at which quantum gravity becomes strong. This in turn can modify the boundary conditions for coupling constant unification, if higher dimensional operators induced by gravity are taken into consideration. We show that the generic size of these effects from gravity can be larger than the two-loop corrections typically considered in renormalization group analyses of unification. In some cases, gravitational effects of modest size can render unification impossible.