tba

TBA

Dark sirens are a powerful way to infer cosmological and astrophysical parameters from the combination of gravitational wave sirens and galaxy catalogues. Importantly, the method relies on the completeness of the galaxy catalogues being well modelled. A magnitude-limited catalogue will always be incomplete to some extent, requiring a completion scheme to avoid biasing the parameter inference. Standard methods include homogeneous and multiplicative completion, which have the advantage of simplicity but underestimate or overestimate the amplitude of structure at low completeness, respectively. In this talk, I will introduce a new method to complete galaxy catalogues which uses clustering information to incorporate knowledge of the large scale structure into the dark sirens method. If the structure of the true number of galaxies is sufficiently well preserved in the catalogue, our estimator can perform drastically better than both homogeneous and multiplicative completion. We lay the foundations for a maximally informative dark sirens analysis.

Cosmological surveys are probing extremely large volumes at ever increasing precision. The dramatic improvement in statistical errors allows us to detect even very subtle effects in the large-scale distribution of matter, and to thoroughly test our theory of gravity on cosmological distance scales. I will present a numerical framework for cosmological N-body simulations that offers a consistent treatment of the dynamics of spacetime as described by the full set of Einstein's equations. Such a framework can be used to compute higher-order correlations in a relativistic setting, or to predict the gravitational dynamics of exotic models that do not offer a simple Newtonian description.

It is now established that about 95% of the energy density of the Universe is made up of Dark Matter (DM) and Dark Energy (DE). Given our limited understanding of their physical nature, an intriguing possibility is to test interactions involving the dark components of the model. In this talk, I will focus on two different categories of interactions: scatter-like interactions between DM and neutrinos, and interacting DE. I will show that both offer interesting perspectives from a theoretical and observational standpoint. I will argue that small-scale Cosmic Microwave Background (CMB) observations can open novel observational windows to accurately test interactions, possibly revealing unique signatures that would be challenging to detect on larger angular scales. Interestingly, several independent CMB observations seem to hint at a mild preference for an interacting dark sector that might help with cosmological tensions.

I will present updated constraints on 'light' Dark Matter (DM) particles with masses between 1 MeV and 5 GeV. In this range, we can expect DM-produced e+/e- pairs to up-scatter low-energy ambient photons in the Milky Way via the inverse-Compton process, and produce a flux of X-rays that can be probed by a range of space observatories. Using diffuse X-ray data from XMM-Newton, INTEGRAL, NuSTAR and Suzaku, we set the strongest constraints to date on annihilating and decaying DM with masses between 150 MeV and 5 GeV.

The Drell-Yan processes pp->ll and pp->lnu at high transverse momentum can provide important probes of semileptonic transitions that are complementary to low-energy flavor physics observables. We derive constraints on the New Physics contributions to these processes by recasting the latest ATLAS and CMS searches for mono- and di-lepton resonances. We then study the interplay between low-energy observables and collider constraints, using the "HighPT" package. Moreover, we investigate the limits of validity of the Standard Model Effective Field Theory (SMEFT) in these regimes by comparing the constraints obtained for some explicit tree-level mediators and their EFT equivalent.