The Emperor's New Arc: gigaparsec patterns abound in a $\Lambda$CDM universe

TL;DR

This paper uses large cosmological simulations to demonstrate that large-scale patterns observed in the universe are consistent with the standard $$CDM model, and that some claimed anomalies are artifacts.

Contribution

The study provides the first large-scale simulation-based validation that observed giant structures are expected in $$CDM, refuting claims of contradictions.

Findings

Large-scale patterns like the 'Giant Arc' are common in $$CDM simulations.

Reported overdensities are likely algorithmic artifacts, not real structures.

The standard model remains consistent with large-scale universe observations.

Abstract

Recent discoveries of apparent large-scale features in the structure of the universe, extending over many hundreds of megaparsecs, have been claimed to contradict the large-scale isotropy and homogeneity foundational to the standard ($\Lambda$CDM) cosmological model. We explicitly test and refute this conjecture using FLAMINGO-10K, a new and very large cosmological simulation of the growth of structure in a $\Lambda$CDM context. Applying the same methods used in the observations, we show that patterns like the "Giant Arc", supposedly in tension with the standard model, are, in fact, common and expected in a $\Lambda$CDM universe. We also show that their reported significant overdensities are an algorithmic artefact and unlikely to reflect any underlying structure.