Abstract
Continuous global symmetries are expected to be broken by gravity, which can lead to important phenomenological consequences. A prime example is the threat that this poses to the viability of the Peccei-Quinn solution to the strong CP problem. In this paper, we explore the impact of wormholes as a source of global symmetry breaking by gravity. We review the current status of wormholes and global symmetries and note that, surprisingly, the axion has a quality problem within non-perturbative Einstein gravity. Although these wormholes lead to a large breaking of global symmetries, we show that their effect is nonetheless relevant for the model building of gauge protected axions. We also find wormhole solutions within two scenarios: (i) an extended global symmetry group within Einstein gravity, and (ii) U(1) wormholes within the low-energy limit of an open String Theory. The former allows us to show that the concept of a global symmetry in General Relativity is somewhat ill-defined. The latter illustrates that for motivated values of the string coupling constant, axions appear to have a quality problem within the open String Theory we consider.
Highlights
The strong CP problem and the axion
We review the current status of wormholes and global symmetries and note that, surprisingly, the axion has a quality problem within non-perturbative Einstein gravity
These wormholes lead to a large breaking of global symmetries, we show that their effect is relevant for the model building of gauge protected axions
Summary
The strong CP problem and the axion. Stringent upper limits on the electric dipole moment of the neutron [1] show that CP is an excellent symmetry of the strong interactions. They showed that the coupling constants in the low energy EFT are exponentially suppressed by the wormhole action, λ ∼ e−S, reflecting the non-perturbative nature of wormholes We will use these operators to quantify the axion quality problem within different particle physics and gravitational scenarios by calculating the values of the wormhole action. We find that the dynamics are again dominated by the wormhole throat and the action given by a sum of two terms of the form log(Mpl/vi) where vi is the symmetry-breaking scale of the field Φi This has important phenomenological consequences for the relevant pseudo-Goldstone bosons. Large additive contributions to the action and potentially solve the axion quality problem via terms of the form S = 8π2/gs, where gs is the string coupling strength Their calculations, were somewhat qualitative and did not directly map into an actual String Theory. Beyond the scope of this paper, it appears that an understanding of whether the radial field might stabilise the wormhole topology is required
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
