Cumulant Correlators from the APM

Abstract

This work presents a set of new statistics, the cumulant correlators (CCs), aimed at high-precision analysis of the galaxy distribution. They form a symmetric matrix, QNM, related to moment correlators in the same way cumulants are related to the moments of the distribution. They encode more information than the usual cumulants SN, and their extraction from data is similar to the calculation of the two-point correlation function. Perturbation theory (PT), its generalization in the extended perturbation theory (EPT), and the hierarchical assumption (HA) have simple predictions for these statistics. As an example, the factorial moment correlators measured by Szapudi and coworkers in the APM catalog are reanalyzed using this technique. While the previous analysis assumed hierarchical structure constants, this method can directly investigate the validity of the HA, along with PT and EPT. The results in agreement with previous findings indicate that, at the small scales used for this analysis, the APM data support the HA. When all nonlinear corrections are taken into account, it is a good approximation at the 20% level. It appears that PT, and a natural generalization of EPT for CCs, does not provide such a good fit for the APM at small scales. Once the validity of the HA is approximately established, CCs can separate the amplitudes of different tree types in the hierarchy up to fifth order. As an example, the weights for the fourth-order tree topologies are calculated including all nonlinear corrections.