How Inflation Might Explain Large-Scale Anisotropy

Brett McInnes

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arXiv · 2608.19765

How Inflation Might Explain Large-Scale Anisotropy

Brett McInnes

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Abstract

Several recent observational analyses have suggested the possible existence of a large-scale anisotropy in our Universe. It is often thought that this would contradict the inflationary picture of the earliest times. We show that this is not the case: if we relax the artificial restriction that spacetime torsion must be zero, then such anisotropies arise naturally, indeed almost inevitably, in a theory of torsional Inflation. This is seen most clearly if one uses a ``$1\,+\,3\,$'' analysis of a torsional spacetime, leading naturally to concepts of intrinsic torsion and extrinsic torsion. An anisotropic quantum fluctuation of the inflaton leads to an extrinsic torsion field which is anisotropic and which grows throughout the inflationary era, even though the intrinsic geometry of the spatial sections is isotropised in the conventional manner. The competition between the intrinsic torsion (which does inflate away) and the extrinsic torsion leads to a short interval, early in the inflationary era, during which there is a torsion-induced energy flux, which leaves an anisotropic signal in superhorizon modes and thus ultimately at large scales in the present Universe.

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Brett McInnes. 2026-08-20. How Inflation Might Explain Large-Scale Anisotropy. https://arxiv.org/abs/2608.19765

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