Abstract: In this talk I will discuss the challenges of modelling dissipative processes in binary neutron star merger simulations, with a focus on reaction-sourced bulk viscosity, likely the dominant dissipative effect. I will begin by reviewing the main hydrodynamic approaches and highlighting the few existing fully non-linear simulations that implement bulk viscosity. I will then explore the connection between reactions and bulk viscosity, from both a thermodynamic and a multi-scale perspective. Finally, I will address the additional complexity introduced by turbulence in mergers, showing how under-resolved turbulent dynamics can shift the effective notion of thermodynamic equilibrium and generate additional effective viscosities, reflecting the subtle ways in which turbulence interacts with microphysical dissipation.

Abstract: A large fraction of the information about galaxy formation is encoded in very faint stellar structures, such as diffuse galaxies, extended stellar halos, and low-mass satellites. These components are extremely difficult to observe, as they lie at surface brightness is well below the limits of most current surveys. The Arrakihs-F2 mission is being designed to specifically target this low surface brightness regime, providing deep optical and near-infrared observations of the nearby Universe. In this talk, I will present the most recent advances in the Arrakihs science case and on the design of the satellite and will also show how the high-resolution cosmological hydrodynamical simulations we are developing in MareNostrum5 under an EuropHPC Extreme Scale project will be used to interpret and support the science goals of Arrakihs. These simulations will allow us for the first time to connect the observed faint stellar light with the underlying distributions of stars, gas, and dark matter, and to quantify which types of objects and structures can realistically be detected. By combining Arrakihs observations with HARKONENS, we aim to place the low surface brightness Universe in a solid physical context and better constrain the processes that shape galaxies at the faint end.

Abstract: Astrophysical anomalies – objects with unusual features, morphologies, or properties – are critical for understanding diverse processes including hierarchical assembly from mergers, environmental effects on galaxies, and cosmological effects such as lensing. To identify rare objects, we developed AnomalyMatch, a semi-supervised machine learning method successfully applied across multiple scales: discovering 57 gravitational lenses among 600,000 JWST sources, 61 jellyfish galaxies in 380,000 Euclid Q1 sources, ~1,000 new anomalies from 99.6 million sources in the Hubble Legacy Archive. We now aim to apply this approach to Euclid’s first data release, where the survey area expands from 63.1 to ~2,000 square degrees and source counts grow from ~30 million to ~1 billion. At this scale, conventional image creation and storage methods become impractical. We therefore introduce Cutana, a parallelized, memory-aware cutout creator generating thousands of images per second. We demonstrate how Cutana and AnomalyMatch work synergistically to enable anomaly detection at unprecedented scales and present our planned projects for Euclid DR1.

Abstract: The LOw Frequency ARray (LOFAR) is one of the world’s leading low-frequency radio telescopes. It consists of dozens of stations across Europe—each comprising hundreds of dipole antennas—with a dense core in the Netherlands. While LOFAR is currently undergoing an upgrade to further enhance its sensitivity, it has already produced a broad range of high-quality scientific results both within and beyond traditional radio astronomy. These include among others studies of radio galaxies, large low-frequency sky surveys, the epoch of reionization and cosmic dawn, cosmic magnetism, pulsars and other transient sources, cosmic rays, lightning, and space weather.

Operating between 10 and 240 MHz, LOFAR must contend with the ionosphere—a region of the upper atmosphere partly ionized by solar radiation—which presents a significant challenge for data calibration. The ionosphere distorts passing electromagnetic waves, and turbulent variations in the electron density make it difficult to correct these distortions. LOFAR’s sensitivity to even the smallest ionospheric structures, though often problematic for astronomers, also offers a unique opportunity: it allows us to probe these fine-scale features directly and gain new insights into ionospheric plasma processes.

In this presentation, I will provide an overview of the LOFAR system and its scientific capabilities, followed by a closer look at the ionospheric data products the telescope can deliver.

Abstract: Entanglement asymmetry is a relative entropy that faithfully measures the breaking of a symmetry in a subregion. We explore some applications in theories with spontaneously broken higher form symmetries. We will start with discrete abelian symmetries and then discuss continuous symmetries. We will be able to recover the Mermin-Wagner-Coleman theorem and refine it for the case of subregions. 

Abstract: Theoretical approaches to large-scale structure strongly depend on the physical regimes considered. On large scales, relativistic effects become important as the standard Newtonian description breaks down. Moreover, these relativistic effects could open a new window for probing the nature of gravity. In this talk, I first show how relativistic galaxy number counts can provide a null test of the weak equivalence principle (EP), and how we can constrain the EP with upcoming Stage-IV surveys in a model-independent way. I then extend this framework to include viscous dark matter, EP violation, and modified gravity, to study whether the EP can still be tested in this context. Interestingly, forecasts for DESI, Euclid, and SKA Phase 2 show that the dark matter viscosity can be constrained at the order of 10^{-6} or better by all three surveys, without assuming the shape of the power spectrum, background evolution, or galaxy bias.