WP1: Development of the gPLUTO code and its resistive GRMHD module
Along with my collaborators at the Physics department of UniTo I first contributed to the development of high-order schemes that significantly increase the computational efficiency of the original version of the PLUTO code. In a first work led by a PhD student I co-supervised (Vittoria Berta), we implemented high-accuracy algorithms for the integration of classical and relativistic ideal magnetohydrodynamics (MHD; Berta et al. 2024, Journal of Computational Physics), leading to an overall increase in effective resolution for a typical astrophysical simulation by at least a factor two. We then extended these results to the relativistic resistive regime (Mignone et al. 2024, MNRAS), which in general requires specific strategies to integrate the stiff differential equations governing the electric field evolution.
During the same period, the PLUTO code has been completely rewritten in C++ and modified to be efficiently run on GPU-accelerated clusters, in collaboration with NVIDIA experts from CINECA. This new version of the code, named "gPLUTO", has been thoroughly tested on pre-exascale EuroHPC machines such as Leonardo (CINECA) and Marenostrum (BSC-CNS), demonstrating an increase in performance with respect to the legacy code of at least one order of magnitude (Rossazza, Mignone, Bugli et al. 2025, submitted to IEEE-TPDS). In a similar fashion, I collaborated with Luca Del Zanna to accelerate the GRMHD code ECHO on GPUs, reaching a similar performance improvement but with a code written in Fortran (Del Zanna et al. 2024, Fluids).
In the meantime, I developed the resistive GRMHD module using first the legacy RMHD module of PLUTO to introduce the standard 3+1 covariant formalism in the code. This allows one to model not only plasma dynamics around a compact object such as a black hole, but also adopt more specific metrics that can be used to model expanding/contracting boxes or the dynamics of a quark-gluon plasma. Later on I ported this module to the GPU-accelerated code gPLUTO, in order to fully exploit its latest developments in term of computational efficiency (Bugli et al. 2025b, to be submitted in A&A).
WP2: Relativistic magnetic reconnection and astrophysical outflows
In collaboration with a master student I co-supervised at the Physics Department of UniTo (Edoardo Lopresti), I adapted a recently proposed prescription for a kinetic formulation of the magnetic diffusivity for the resistive relativistic MHD framework. I then led a collaboration with Benôit Cerutti (renown expert of kinetic models and magnetic reconnection) from the "Institut de Planétologie et d'Astrophysique de Grenoble" (IPAG) to validate our prescription against first-principles Particle-In-Cell (PIC) simulations (Bugli et al. 2025, A&A). On top of obtaining an exceptional agreement between our fluid models with effective resistivity and the PIC simulations in terms of dynamics of the reconnecting current sheet, thanks to hybrid RMHD-PIC models we verified that charged particles are also accelerated in a very similar fashion when a more realistic magnetic dissipation is taken into account (Lopresti, Bugli et al. 2025, to be submitted in A&A). We are also currently testing the fundamental properties of relativistic magnetic reconnection performing 3D high-order RMHD models, which show how the onset of plasma instabilities along the current sheet can qualitatively affect the properties of magnetic dissipation (Berta, Bugli et al. 2025, to be submitted in A&A).
In connection to large-scale astrophysical simulations of relativistic plasmas, I contributed to one of the first systematic studies of gamma-ray burst jets with a finite conductivity, showcasing the qualitative impact of magnetic dissipation on the jet's dynamics and the morphology of the current sheets where particle acceleration by magnetic reconnection can occur (Mattia, Del Zanna, Bugli et al. 2023, A&A). I further explored the impact of magnetic fields in connection to the formation of compact objects during the onset of extreme core-collapse supernovae, highlighting their central role in determining the expected neutrino signals (Bendahman et al. 2023, JCAP) and the associated formation of new heavy elements during the explosive nucleosynthesis (Reichert, Bugli et al. 2024, MNRAS). Finally, I am currently leading a code comparison project focused on highly magnetized core-collapse simulations, where together with other 4 independent research groups I demonstrate how different codes can qualitatively reproduce the same dynamics for the explosion and the magnetic fields, although presenting quantitative deviations in the evolution of key diagnostics such as explosion energy and ejecta collimation (Bugli et al. 2025c, to be submitted in A&A).
