Constraining Inflation Models with Spinning Voids

TL;DR

This paper introduces a new method using the rotation of void galaxies to constrain the running of the scalar spectral index, providing a novel observational tool for understanding inflation models.

Contribution

It develops a universal model for void galaxy redshift asymmetry that is sensitive to the running of the spectral index, linking cosmological inflation theories with observable galaxy dynamics.

Findings

The model is nearly universal across various cosmologies.

Deviations in the running of the spectral index affect void asymmetry predictions.

The diagnostics can distinguish between standard and non-standard inflation models.

Abstract

We present a powerful new diagnostics by which the running of scalar spectral index of primordial density fluctuations can be tightly and independently constrained. This new diagnostics utilizes coherent rotation of void galaxies, which can be observed as redshift asymmetry in opposite sides dichotomized by the projected spin axes of hosting voids. Comparing the numerical results from the AbacusSummit of cosmological simulations, we derive a non-parametric model for the redshift asymmetry distribution of void galaxies, which turns out to be almost universally valid for a very broad range of cosmologies including dynamic dark energy models with time-dependent equation of states as well as the $\Lambda$CDM models with various initial conditions. We discover that the universality of this model breaks down only if the running of scalar spectral index deviates from zero, detecting a consistent trend that a more positive (negative) running yields a lower (higher) redshift asymmetry of voids than the model predictions. Given that non-standard inflations usually predict non-zero runnings of the spectral index and that the redshift asymmetry distribution of voids is a readily observable quantity, we conclude that this new diagnostics will pave another path toward understanding the true mechanism of inflation.