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      Could Sample Variance be Responsible for the Parity-Violating Signal Seen in the BOSS Galaxy Survey?


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          Recent works have uncovered an excess signal in the parity-odd four-point correlation function measured from the BOSS spectroscopic galaxy survey. If physical in origin, this could indicate evidence for new parity-breaking processes in the scalar sector, most likely from inflation. At heart, these studies compare the observed four-point correlator to the distribution obtained from parity-conserving mock galaxy surveys; if the simulations underestimate the covariance of the data, noise fluctuations may be misinterpreted as a signal. To test this, we reanalyse the BOSS CMASS + LOWZ parity-odd dataset with the noise distribution modeled using the newly developed GLAM-Uchuu suite of mocks. These comprise full N-body simulations that follow the evolution of \(2000^3\) dark matter particles in a \(\Lambda\)CDM universe, and represent a significant upgrade compared to the formerly MultiDark-Patchy mocks, which were based on an alternative (non N-body) gravity solver. We find no significant evidence for parity-violation in the BOSS dataset (with a baseline detection significance of \(1.4\sigma\)), suggesting that the former signal (\(>3.5\sigma\) with our data cuts) could be caused by an underestimation of the covariance in MultiDark-Patchy. The significant differences between results obtained with the two sets of BOSS-calibrated galaxy catalogs showcases the heightened sensitivity of beyond-two-point analyses to the treatment of non-linear effects and indicates that previous constraints may suffer from large systematic uncertainties.

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          17 January 2024


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          7 pages, 4 figures, submitted to Phys. Rev. D
          astro-ph.CO astro-ph.GA gr-qc hep-ph hep-th

          Cosmology & Extragalactic astrophysics,General relativity & Quantum cosmology,Galaxy astrophysics,High energy & Particle physics


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