On the robustness of the angular homogeneity scale $\theta_H$: a comparative analysis of computational approaches

Abstract

The assumption of large-scale homogeneity is a cornerstone of modern cosmology and underlies the validity of the FLRW framework. Testing the scale at which the Universe transitions to homogeneity remains a key observational challenge, particularly with the increasing precision of galaxy surveys. We aim to assess the robustness of the angular homogeneity scale, $\theta_H$, by systematically comparing different computational approaches used in its estimation and by quantifying the impact of methodological choices and physical clustering scales. We analyse mock galaxy catalogues from the MICE Grand Challenge simulation. The angular fractal dimension $D_2(\theta_H)$ is computed using the Landy-Szalay estimator and direct pair-counting methods. We implement different approaches, including symbolic regression, to model $D_2(\theta_H)$ and determine $\theta_H$. Uncertainties are estimated using resampling techniques and alternative parametric error propagation methods. We find that the estimation of $\theta_H$ is sensitive to methodological choices in the analysis, such as survey area, redshift bin, numerical implementation and fitting strategy. While its redshift evolution is robust, its absolute value is sensitive to both modelling choices and the presence of local clustering features. Our results highlight the importance of methodological systematics in homogeneity studies, showing that the determination of $\theta_H$ depends not only on the data, but also on the adopted analysis strategy. Flexible approaches such as symbolic regression provide a useful framework to model these effects, but also emphasize the need for careful modelling and survey design. This has important implications for future large-scale structure analyses aiming to test the Cosmological Principle with high precision.