The Persistence of Large Scale Structures I: Primordial non-Gaussianity

TL;DR

This paper introduces a topological data analysis method using persistent homology to detect primordial non-Gaussianity in large-scale cosmic structures, providing a new approach that complements existing techniques and offers interpretable results.

Contribution

The authors develop a novel pipeline applying persistent homology to cosmological data, enabling detection of primordial non-Gaussianity without relying on long-wavelength mode sampling.

Findings

Detects local non-Gaussianity parameter $f_{NL}^{loc}=10$ with 97.5% confidence in large volumes

Able to distinguish non-Gaussian signals from variations in $\sigma_8$ using an optimal template method

Provides new predictions for topological features like filament loops in dark matter distributions

Abstract

We develop an analysis pipeline for characterizing the topology of large scale structure and extracting cosmological constraints based on persistent homology. Persistent homology is a technique from topological data analysis that quantifies the multiscale topology of a data set, in our context unifying the contributions of clusters, filament loops, and cosmic voids to cosmological constraints. We describe how this method captures the imprint of primordial local non-Gaussianity on the late-time distribution of dark matter halos, using a set of N-body simulations as a proxy for real data analysis. For our best single statistic, running the pipeline on several cubic volumes of size $40~(\rm{Gpc/h})^{3}$, we detect $f_{\rm NL}^{\rm loc}=10$ at $97.5\%$ confidence on $\sim 85\%$ of the volumes. Additionally we test our ability to resolve degeneracies between the topological signature of $f_{\rm NL}^{\rm loc}$ and variation of $\sigma_8$ and argue that correctly identifying nonzero $f_{\rm NL}^{\rm loc}$ in this case is possible via an optimal template method. Our method relies on information living at $\mathcal{O}(10)$ Mpc/h, a complementary scale with respect to commonly used methods such as the scale-dependent bias in the halo/galaxy power spectrum. Therefore, while still requiring a large volume, our method does not require sampling long-wavelength modes to constrain primordial non-Gaussianity. Moreover, our statistics are interpretable: we are able to reproduce previous results in certain limits and we make new predictions for unexplored observables, such as filament loops formed by dark matter halos in a simulation box.