Cosmic voids

Wed, 29 Jul 2026 00:00:00 +0000

A major research theme has been the study of cosmic voids — vast, under-dense regions occupying most of the volume of the Universe. When I began working on my Master’s thesis, the community had theoretically demonstrated that the statistical properties of these structures could be exploited to constrain dark energy and test theories of gravity, but the theoretical models describing the void size distribution consistently failed to predict both simulated and observed data.

My work has paved the way for the cosmological exploitation of the void size function when voids are identified in any distribution of tracers, including real data catalogues. In Ronconi & Marulli (2017) we presented an algorithm that redefines void ridges and, consequently, their radii; I implemented it inside CosmoBolognaLib, a large set of open-source numerical libraries for cosmological calculations.

With this tool we then demonstrated that, as long as our specifications are accounted for, the size function is a viable approach for studying cosmology with cosmic voids. The result was further validated by its adoption as a fundamental tool in Key Projects within the Euclid Collaboration, used to forecast the cosmological constraining power of void statistics.

Currently: I am working with members of the Euclid Collaboration on void statistics in mock galaxy catalogues, and investigating a new theoretical model of the void distribution based on stochastic differential equations, together with Andrea Lapi at SISSA. A Ph.D. student has recently been selected to pursue this direction over the next three years under our supervision.

Key papers: · · ·

Software: CosmoBolognaLib

CosmoBolognaLib

Wed, 01 Nov 2017 00:00:00 +0000

Role: contributor — void size function modelling and void-catalogue cleaning. Stack: C++ libraries with a SWIG-generated Python wrapper. Author & maintainer: Federico Marulli (Università di Bologna).

CosmoBolognaLib (CBL) is a living project that provides a common numerical environment for cosmological investigations of the large-scale structure of the Universe. Its focus is handling astronomical catalogues — real and simulated — measuring one-, two- and three-point statistics in configuration space, and running cosmological analyses.

My contribution is the set of tools for cosmic voids: the algorithm that redefines void ridges and therefore their radii, together with the model for the void size function. The cleaning procedure takes a void catalogue produced by a void finder and returns a catalogue of non-overlapping spheres, each embedding a fixed density contrast in the tracer density field — which is what makes the measured size function comparable with theoretical predictions. These functions were released in CBL v3.2 and are credited in the library’s changelog to Ronconi & Marulli (2017).

The tooling underpins the void work described in my , and was subsequently adopted in Key Projects within the Euclid Collaboration to forecast the cosmological constraining power of void statistics.

The void tools are presented in Astronomy & Astrophysics 607, A24 (2017) — see . The library itself is described in Marulli, Veropalumbo & Moresco (2016).

Large-Scale Structure |

Cosmic voids

CosmoBolognaLib