![Helicity asymmetries of the primordial (left panel) and late-time (right panel) density fields for parity asymmetric (blue curves) and symmetric (red curves) simulations. The shaded regions indicate the standard deviation (1σ) of the ensemble-average. The red markers highlight the asymmetries exceeding a statistical significance of 3σ. - [astro-ph.CO]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Probing.png?fit=1200%2C674&ssl=1)
[astro-ph.CO] Whether parity symmetry was violated in the early universe remains one of the fundamental open questions in cosmology. If so, it may leave an intrinsic handedness in the large-scale matter distribution.
Here we formulate a helicity-based estimator to measure this handedness. Using cosmological simulations with parity-violating initial conditions, we show that it survives nonlinear structure formation.
Applying the estimator to density fields reconstructed from the SDSS DR7 galaxy catalog, we find mild deviations but statistically insignificant evidence for parity violation in the local universe.
Our results establish the intrinsic handedness of the matter distribution as an observable relic of primordial parity violation, enabling a direct probe with current and future large-scale structure surveys.
Fang-Na Shao, Hao-Ran Yu, Ming-Jie Sheng, Bing-Hang Chen, Huiyuan Wang
Comments: 4 pages, 2 figures. Comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:2607.26612 [astro-ph.CO] (or arXiv:2607.26612v1 [astro-ph.CO] for this version)
https://doi.org/10.48550/arXiv.2607.26612
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Submission history
From: Hao-Ran Yu
[v1] Wed, 29 Jul 2026 08:37:27 UTC (105 KB)
https://arxiv.org/abs/2607.26612
Astrobiology,
