There is another paper on „Efficient computation of N-point correlation functions in D dimensions“ at https://www.pnas.org/doi/10.1073/pnas.2111366119 https://w

There is another paper on „Efficient computation of N-point correlation functions in D dimensions“ at https://www.pnas.org/doi/10.1073/pnas.2111366119 https://www.pnas.org/doi/10.1073/pnas.2111366119 „This work considers NPCF estimation on isotropic and homogeneous manifolds in D dimensions. Under these assumptions (which encompass spherical, flat, and hyperbolic geometries), we show that any function of one position can be expanded in hyperspherical harmonics; a D-dimensional analog of the conventional spherical harmonics. “ So it seem they must assume a homogeneous and isotopic universe to be able to do their analysis.