Is the baryon acoustic oscillation peak a cosmological standard ruler?

TL;DR

This paper investigates whether the BAO peak remains a reliable standard ruler in cosmology, considering effects of gravitational collapse that may cause spatial inhomogeneity in its measurement.

Contribution

It provides observational evidence that the BAO peak location varies with environment, challenging its use as a fixed standard ruler in the standard cosmological model.

Findings

BAO peak compression correlates with supercluster overlap

Significant spatial variation in BAO peak location detected

Implications for future cosmological survey calibration

Abstract

In the standard model of cosmology, the Universe is static in comoving coordinates; expansion occurs homogeneously and is represented by a global scale factor. The baryon acoustic oscillation (BAO) peak location is a statistical tracer that represents, in the standard model, a fixed comoving-length standard ruler. Recent gravitational collapse should modify the metric, rendering the effective scale factor, and thus the BAO standard ruler, spatially inhomogeneous. Using the Sloan Digital Sky Survey, we show to high significance (P < 0.001) that the spatial compression of the BAO peak location increases as the spatial paths' overlap with superclusters increases. Detailed observational and theoretical calibration of this BAO peak location environment dependence will be needed when interpreting the next decade's cosmological surveys.