Physical remnant of electroweak theta angles

TL;DR

This paper introduces a new electroweak theta angle in the Standard Model, invariant under chiral rotations, which could have observable effects in non-trivial spacetime topologies.

Contribution

It identifies a previously unrecognized electroweak theta angle as an independent parameter, expanding the understanding of Standard Model topological features.

Findings

The new theta angle is invariant under chiral rotations.

It can be associated with observable effects in non-simply connected spacetime.

Potential implications for laboratory and cosmological observations.

Abstract

In addition to the well-known quantum chromodynamical theta angle, we show that the Standard Model has another theta angle which is invariant under arbitrary chiral rotations of quarks and leptons. The new theta angle can be identified with the quantum electrodynamical theta angle, which should be viewed as an independent parameter of the Standard Model, and may be observable in spacetime with non-simply connected features, either beyond the visible universe or in an effective background from a laboratory setup.