The Cosmological Dipole in Tilted Anisotropic Universes

TL;DR

This paper investigates the cosmic dipole anomaly within tilted anisotropic universe models, analyzing various scenarios and their effects on cosmological observations, and finds that most models cannot explain the observed dipole without additional exotic physics.

Contribution

It explores the cosmic dipole in tilted anisotropic universes considering multiple scenarios, identifying limitations in explaining the anomaly without new physics.

Findings

Most models cannot produce the observed dipole amplitude.

The Khronon field case can potentially explain the dipole.

Additional exotic physics are needed for a full explanation.

Abstract

There is tentative evidence for a mismatch between the rest frames of matter and the cosmic microwave background, the "quasar dipole anomaly". We consider such a dipole in tilted anisotropic models, for a range of scenarios and sources: spatial curvature, cosmic heat flux, large scale electromagnetic fields and a Khronon field. Crucially, we determine the ancillary effects on other cosmological observables in each of these models and we show that, apart from the case of the Khronon field, it is unlikely that one can obtain a dipole with the amplitude that is being observed unless one considers additional exotica.