We explore physics beyond the Standard Model of cosmology, as mounting observational tensions challenge the ΛCDM paradigm. Discrepancies such as the Hubble constant tension, unexpected cosmic dipole measurements, and the discovery of surprisingly bright, ancient galaxies by the James Webb Space Telescope indicate that fundamental assumptions about cosmic evolution may be incomplete. Instead of merely adjusting parameters within ΛCDM, we are investigating deeper theoretical extensions that go beyond the standard framework.

One avenue involves developing new theoretical descriptions of dark energy and modified gravity, incorporating additional degrees of freedom beyond the metric field (e.g., the effective field theory of dark energy). Another approach questions foundational cosmological principles, seeking alternative frameworks to describe cosmic evolution. For instance, we refine models based on non-standard  metric and introduce a novel observable—the three-dimensional expansion rate fluctuation field η—to probe deviations from isotropy. Analysis of galaxy and supernova datasets has revealed unexpected large-scale symmetries in cosmic expansion, suggesting the need for model-independent methods to connect these findings to fundamental cosmographic parameters.

A more speculative yet essential direction explores macroscopic quantum gravitational effects on cosmology. By examining how quantum fluctuations in the metric influence causality and the lightcone structure, we aim to uncover their implications for early-universe physics.

Together, these efforts push beyond ΛCDM, searching for new physics that could redefine our understanding of cosmic spacetime and its evolution.

The gravitational evolution of matter shapes the large-scale structure of the universe, organizing galaxies across cosmic distances. By studying the clustering of galaxies, we gain insight into the statistical properties of the underlying matter field. Extracting cosmological information relies on defining measurable observables that characterize the large-scale distribution of galaxies.

At CPT, we develop innovative observables—such as for example the Clustering Ratio—designed to probe fundamental cosmological parameters, including neutrino mass, spatial curvature, the local expansion rate, and the total matter content of the universe. Our work encompasses theoretical modeling, tests for astrophysical systematics, and applications to key cosmological surveys like SDSS and VIPERS. Additionally, we contribute to the study of large-scale observables and their higher-order statistical properties through cosmological simulations.

To remain at the forefront of galaxy clustering research, we are actively involved in the Euclid collaboration. Launched in July 2023, Euclid is a space telescope equipped with both photometric and spectroscopic instruments. Our team plays a key role in working groups dedicated to analyzing Euclid’s data, extracting cosmological insights through two-point statistics and Baryon Acoustic Oscillations. Furthermore, our involvement in Euclid provides a valuable framework for exploring the interplay between galaxy clustering and gravitational wave experiments.

Gravitational waves are a key prediction of Einstein’s General relativity: propagating “ripples” in spacetime, produced by accelerating binaries systems made of the most compact objects in the Universe - black holes and neutron stars. Following the first direct detection in 2015, gravitational-wave astronomy is today an emerging yet quickly expanding field. Hundreds of new detections are under way every year, with thousands and then millions per year expected in the next decade. These numbers are turning the field in a big data discipline that will be soon be able to deliver precision science.

We are interested in using gravitational waves as a tool for advancing fundamental physics, astrophysics, and cosmology.

In cosmology, gravitational waves are “standard sirens” - they provide a direct measurements of the luminosity distance of the source. This makes them novel probes of the Universe’s expansion and a new observable to test General Relativity on cosmological scales. Leveraging both bright and dark sirens, namely sources with and without a direct redshift determination, we are interested in combining gravitational-wave data with galaxy surveys to extract cosmological information to address pressing open questions like the Hubble tension. Our methods integrate advanced statistical techniques, such as Bayesian inference and machine learning, to overcome computational and methodological challenges and scale to the massive datasets expected from future detectors. We contribute to the Virgo collaboration, currently in a data taking period.

We are deeply involved in the European Einstein Telescope (ET) project as part of the Observational Science Board. We contribute to optimizing ET’s design and scientific goals through tools like GWFAST, a Fisher matrix-based Python code for forecasting detection capabilities and parameter estimation. Our work spans diverse applications, from multimessenger astronomy to fundamental tests of gravity.

Involved members: M. Mancarella, S. Bera, V. De Renzis, A. Agapito, A. Pedrotti