Somewhat excited about teaching to our undergrad students today how the velocity field of a fluid can always be decomposed into a scalar (expansion/compression), a vector (rotation), and a tensor (shear) part. Simple and yet profound...

Proud moment: very hard work by Florian List (also w/ L. Winkler and T. Floess): our super-fast differentiable N-body framework "DISCO-DJ" had a first release (github.com/cosmo-sims/D...) and a massive paper (arxiv.org/abs/2510.05206) - we'll use it to fit simulations to our Universe... #cosmology

Everything has to end. Many exciting talks and discussions how to extract maximum information about #cosmology from #galaxy-surveys and realise the promise of full #field-level-inference during our workshop @esivienna.bsky.social .... videos here (more to come): www.youtube.com/playlist?lis...

Very excited to kick off our workshop at @esivienna.bsky.social on "Putting the cosmic large-scale structure on the map" today. Looking forward to a week of discussions around extracting the maximum of cosmological information from astronomical observations. Amazing support by the ESI team. Thanks!

First time I get to visit Geneva observatory. Really cool idea to have a mock up of the #VLT on display illustrating its immense size (and providing a nice shaded picnic area). Unbelievable that #ELT will be almost 5x larger in diameter...

Very lucky to teach at the fantastic summer school on 'The Dark Universe' in Les Houches today. Cosmology, good discussions, and most beautiful scenery, what more would you want... Lectures and recordings available from indico.iap.fr/event/25/ove... #cosmology #summerschool #darkuniverse

The second day of the Vienna #ISAPP summer school on gravitational waves @esivienna.bsky.social starts with Zoltan Haiman’s lecture on the many exciting questions we can tackle in the new era of multimessenger astronomy.

Very excited that the #ISAPP 2025 summer school on gravitational waves is happening in Vienna for the next two weeks. Great introductory lecture by Clifford Will today…

Final weekly problem set for our methods of computational astrophysics class in Vienna: self-gravitating Vlasov-Poisson dynamics with a symplectic PIC method and spectral Poisson solver. Dear students, we've come a long way!

to me there is a profound beauty in the irreversibility of the inviscid Burgers equation: thou shalt not create information from nothing! mathematically it is reversible, physically it is not

Google search used to be great for quick boring unit conversion calculations, but now it's just giving wrong results? Bug or shitty AI? (critical density is 2.775e11 h^2 Msun/Mpc^3 not 4.8e9)

Looking forward to teaching students about numerical methods for diffusion problems, including anisotropic and anomalous diffusion, in our 'methods of computational astrophysics course' today...

Just playing with shaders... Complex roots of unity with Newton method = Newton fractal. twigl.app?ol=true&ss=-...