Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings

TL;DR

This paper proposes that large-scale quasar polarization alignments can be explained by gravitational effects of warped cosmic strings in a five-dimensional spacetime, which induce persistent disturbances affecting observable polarization patterns.

Contribution

It introduces a model where warped cosmic strings in 5D spacetime produce gravitational disturbances that influence quasar polarization alignments, linking higher-dimensional physics to observable cosmological phenomena.

Findings

Warped cosmic strings induce long-lasting gravitational disturbances.

These disturbances can explain the observed polarization alignments.

The model suggests a connection between extra dimensions and large-scale cosmic structures.

Abstract

The recently discovered alignment of quasar polarizations on very large scales could possibly explained by considering cosmic strings on a warped five dimensional spacetime. Compact objects, such as cosmic strings, could have tremendous mass in the bulk, while their warped manifestations in the brane can be consistent with general relativity in 4D. The self-gravitating cosmic string induces gravitational wavelike disturbances which could have effects felt on the brane, i.e., the massive effective 4D modes (Kaluza-Klein modes) of the perturbative 5D graviton. This effect is amplified by the time dependent part of the warp factor. Due to this warp factor, disturbances don't fade away during the expansion of the universe. From a non-linear perturbation analysis it is found that the effective Einstein 4D equations on an axially symmetric spacetime, contain a "back-reaction" term on the righthand side caused by the projected 5D Weyl tensor and can act as a dark energy term. The propagation equations to first order for the metric components and scalar-gauge fields contain $\varphi$-dependent terms, so the approximate wave solutions are no longer axially symmetric. The disturbances, amplified by the warp factor, can possess extremal values for fixed polar angles. This could explain the two preferred polarization vectors mod $(\varphi, 90^o)$.