How Inflation Might Explain Large-Scale Anisotropy

Abstract

Several recent observational analyses have suggested the possible existence of anisotropy in our Universe. It is often thought that this would contradict the inflationary picture. We have argued 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. This leads to an anisotropic Hubble field at the \emph{end} of Inflation. The anisotropy takes a very specific and characteristic form, which in principle could be observable on relatively short cosmic scales. On the other hand, an unusual feature of torsional geometry leads to a short interval, \emph{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 very large scales in the present Universe. Thus in principle torsion can explain anisotropies both on relatively short cosmic scales and also at the largest scales.

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BibTeX RIS

BibTeX

@misc{mcinnes2026inflation,
  title = {{How Inflation Might Explain Large-Scale Anisotropy}},
  author = {Brett McInnes},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2608.19765},
  eprint = {2608.19765},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.19765},
}

RIS

TY  - UNPB
TI  - How Inflation Might Explain Large-Scale Anisotropy
AU  - Brett McInnes
PY  - 2026
DA  - 2026/09/20
PB  - arXiv
DO  - 10.48550/arxiv.2608.19765
UR  - https://arxiv.org/abs/2608.19765
AB  - Several recent observational analyses have suggested the possible existence of anisotropy in our Universe. It is often thought that this would contradict the inflationary picture. We have argued 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. This leads to an anisotropic Hubble field at the \emph{end} of Inflation. The anisotropy takes a very specific and characteristic form, which in principle could be observable on relatively short cosmic scales. On the other hand, an unusual feature of torsional geometry leads to a short interval, \emph{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 very large scales in the present Universe. Thus in principle torsion can explain anisotropies both on relatively short cosmic scales and also at the largest scales.
ER  -

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