CMB B-modes, spinorial space-time and Pre-Big Bang (II)

TL;DR

This paper explores alternative explanations for CMB B-mode polarization, suggesting that pre-Big Bang cosmologies and spinorial space-time could account for observations without invoking cosmic inflation or primordial gravitational waves.

Contribution

It introduces the spinorial space-time framework and pre-Big Bang models as viable alternatives to inflation for explaining CMB B-modes and related early Universe phenomena.

Findings

Spinorial space-time predicts a privileged space direction consistent with Planck data.

Pre-Big Bang models can generate gravitational waves without inflation.

Alternative cosmologies may explain BICEP2 results without primordial gravitational waves.

Abstract

The BICEP2 collaboration reported recently a B-mode polarization of the cosmic microwave background (CMB) radiation inconsistent with the null hypothesis at a significance of > 5 {\sigma}. This result has been often interpreted as a signature of primordial gravitational waves from cosmic inflation, even if actually polarized dust emission may be at the origin of such a signal. Even assuming that part of this CMB B-mode polarization really corresponds to the early Universe dynamics, its interpretation in terms of inflation and primordial gravitational waves is not the only possible one. Alternative cosmologies such as pre-Big Bang patterns and the spinorial space-time (SST) we introduced in 1996-97 can naturally account for such CMB B-modes. In particular, the SST automatically generates a privileged space direction (PSD) whose existence may have been confirmed by Planck data. If such a PSD exists, it seems normal to infer that vector perturbations have been present in the early Universe leading to CMB B-modes in suitable cosmological patterns. Inflation would not be required to explain the BICEP2 result assuming it really contains a primordial signal. More generally, pre-Big Bang cosmologies can also generate gravitational waves in the early Universe without any need for cosmic inflation. We further discuss here possible alternatives to the inflationary interpretation of a primordial B-mode polarization of cosmic microwave background radiation.