Cosmographic constraints on a G\"odel-type rotating universe

TL;DR

This study explores the possibility of cosmic rotation using a G"odel-type model constrained by Type Ia supernova data, finding mild evidence for rotation and suggesting it could impact the universe's expansion.

Contribution

It introduces a cosmographic analysis of supernova data to constrain a rotating universe model, providing new insights into cosmic rotation's observational signatures.

Findings

Mild preference for cosmic rotation in supernova data

Rotation parameter $\

Hubble constant remains stable across redshifts

Abstract

We investigate the possibility of global cosmic rotation using a G\"odel-type rotating cosmological model, constrained through a cosmographic analysis of Type Ia supernovae (SNIa) from the Pantheon+ dataset. Employing a Taylor-expanded apparent magnitude--redshift relation derived via the Kristian-Sachs formalism, we analyze low-redshift SNIa data across five redshift bins (up to $Z \leq 0.5$). Our results reveal a mild but consistent preference for cosmic rotation, with the dimensionless rotation parameter $\Omega_0$ peaking at $0.29^{+0.21}_{-0.15}$ for $Z \leq 0.2$, and a broadly aligned anisotropy axis centered around equatorial coordinates $(243^\circ, -49^\circ)$. The inferred Hubble constant $h_0 \approx 0.73$ remains stable across all bins, while the deceleration parameter $q_0$ trends from near-zero to mildly negative values with increasing redshift. Model comparison using the Akaike Information Criterion (AIC) indicates a statistically significant preference for the rotating model over the standard $\Lambda$CDM cosmology at intermediate redshifts. These findings suggest that cosmic rotation, if present, may influence the late-time expansion history of the universe and warrants further investigation beyond the cosmographic regime.