'Tilting' the Universe with the Landscape Multiverse: The 'Dark' Flow

TL;DR

This paper proposes that superhorizon inhomogeneities from the landscape multiverse induce a bulk flow and low multipole anisotropies in the CMB, potentially explaining the observed 'dark' flow as a probe of preinflationary physics.

Contribution

It introduces a model linking landscape multiverse remnants to observable CMB anisotropies and bulk flows, providing testable predictions for preinflationary inhomogeneities.

Findings

Predicted bulk flow velocity of about 700 km/s matches observations.

Induced CMB multipoles, especially dipole and quadrupole, align with a preferred axis.

Characteristic scale of potential modification is approximately 10^3 times the Hubble radius.

Abstract

The theory for the selection of the initial state of the universe from the landscape multiverse predicts superhorizon inhomogeneities induced by nonlocal entanglement of our Hubble volume with modes and domains beyond the horizon. Here we show these naturally give rise to a bulk flow with correlation length of order horizon size. The modification to the gravitational potential has a characteristic scale $L_{1} \simeq 10^{3} H^{-1}$, and it originates from the preinflationary remnants of the landscape. The 'tilt' in the potential induces power to the lowest CMB multipoles, with the dominant contribution being the dipole and next, the quadrupole. The induced multipoles $l \le 2$ are aligned with an axis normal to their alignment plane being oriented along the preferred frame determined by the dipole. The preferred direction is displayed by the velocity field of the bulk flow relative to the expansion frame of the universe. The parameters are tightly constrained thus the derived modifications lead to robust predictions for testing our theory. The 'dark' flow was recently discovered by Kashlinsky et al. to be about $700 km/s$ which seems in good agreement with our predictions for the induced dipole of order $3 \mu K$. Placed in this context, the discovery of the bulk flow by Kashlinsky et al. becomes even more interesting as it may provide a probe of the preinflationary physics and a window onto the landscape multiverse.