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On June 2nd 2025, Roberta Duarte defended her PhD on operator learning applied to magnetohydrodynamics.

Operator learning is a cutting-edge machine learning technique where we devise a model to learn the operator solution of partial differential equations rather than learning the solutions themselves. Roberta adapted the Fourier neural operator technique to learn to forecast the time evolution of the Orszag-Tang vortex, a classical problem in MHD and used to benchmark and test every numerical MHD code that exists because of the onset of turbulence and shocks.

Roberta beautifully gave her PhD thesis talk and handled questions from the five committee members. The defense started at 2:15pm local time, and ended at 6pm. Yes, a long defense, with rich conversations and discussions.

Congratulations, Dr. Duarte!

We submitted a paper reporting these results. Stay tuned for news.

Today we had the outstanding MsC defense of Pedro Naethe Motta, entitled “GRMHD simulations of X-ray binaries in the hard state“. There is a lot to unpack here: GRMHD stands for general relativistic magnetohydrodynamic, a technique used by astrophysicists to simulate the motion of plasmas in curved spacetimes.

In this work, Pedro presented a new, computationally efficient method for modeling the radiation processes in black hole X-ray binaries (XRBs), developed using a feature of GPUs called texture memory instead of lookup tables or directly solving the cooling equations. In the dissertation, Pedro extensively tested the new approach and implemented it in the H-AMR GRMHD code. This new approach can be quite useful for studying accretion flows around stellar-mass black holes.

During his masters, Pedro spent five months visiting our collaborator Sasha Tchekhovskoy at Northwestern University who is one of the main groups developing and using H-AMR.

Stay tuned for a paper reporting the results of this work!

Today, Lucas Siconato made a fantastic MsC defense, presenting his work analyzing and modeling the gamma-ray spectrum of Sagittarius A*—the supermassive black hole in the Milky Way—using over ten years of observations made with the Fermi Large Area Telescope. Lucas modeled the observations using both leptonic and hadronic scenarios, and the results are intriguing.

Congrats, Lucas! We wish you a fantastic career.

I am so so happy that one of the best students I have had the pleasure of working with throughout the years, Ivan Almeida, beautifully defended his FAPESP-funded PhD today, entitled “Winds and feedback from supermassive black holes accreting at low rates”. This was a long journey where I learned more from Ivan than him from me. Ivan finished his graduate school with many first author papers spanning numerical simulations of winds, analytical models, and data modeling using different techniques.

Ivan got multiple postdoc offers, with Asia and Europe competing for him. In the end, his next step will be at Newcastle University. A dramatic change of scenery compared to São Paulo. We wish you a productive and happy career.