Gravity cannot tell left from right: standard gravitational evolution of Gaussian initial conditions preserves parity, so any parity violation found in the three-dimensional galaxy distribution must have been present at birth or come from new physics. Two independent analyses of the BOSS galaxy four-point correlation function reported exactly that: Philcox (2022, arXiv:2206.04227) found parity violation at 2.9 sigma, while Hou, Slepian and Cahn (2023) reported significances up to 7 sigma using related but distinct estimators. The four-point function is the lowest-order statistic that can carry parity information in 3D, because four points define a tetrahedron, the simplest shape with a handedness.
The result, if physical, is revolutionary, which is precisely why the scrutiny has been severe. The significance estimates depend on covariance matrices built from mock catalogs, and subsequent reanalyses argue the mocks do not faithfully reproduce the statistical properties of the data, with at least one analysis concluding there is no compelling evidence for parity violation in BOSS once covariance uncertainties are treated conservatively. Systematic tests reveal no observational artifact, so the dispute is genuinely statistical: a possibly real signal versus possibly underestimated noise. ΛCDM has no stake in survival here; it simply forbids the signal, so confirmation would require parity-violating primordial physics that the model does not contain.
The standing awaits DESI: Cahn et al. forecast that a genuine signal will reach decisive significance with DESI Year 5 luminous red galaxies, and composite-field spectra of BOSS and DESI LRGs are already being tested (arXiv:2604.06021). Within a few years the galaxy 4PCF will either deliver the first detection of cosmological parity violation in large-scale structure or retire the claim as a covariance artifact.