Moritz Fischer

New PhD position on self-interacting dark matter available in Hamburg!
v22.desy.de/e67416/recor...

View of a building at the Donostia International Physics Centre. The logo with the letters DIPC can be seen on the façade.

I am delighted to have started this week as a Feodor Lynen Fellow of the Alexander von Humboldt Foundation (@humboldt-foundation.de) at the Donostia International Physics Centre (@dipcehu.bsky.social) in San Sebastián, working in Raúl Angulo's group.

Today, I had the pleasure to review the state of the art in simulations of self-interacting dark matter at the SIDM workshop in Valencia.
indico.ific.uv.es/event/7815/

To collapse or not to collapse: Halo evolution with self-interacting dark matter mass segregation Surprisingly compact substructures in galaxies and galaxy clusters, but also field halos, have been observed by gravitational lensing. They could be difficult to explain with collisionless dark matter...

To collapse or not to collapse? A study led by my student Yashraj Patil on the evolution of a self-interacting dark matter halo with two dark matter species.
arxiv.org/abs/2506.06272

Accurately simulating core-collapse self-interacting dark matter halos The properties of satellite halos provide a promising probe for dark matter (DM) physics. Observations motivate current efforts to explain surprisingly compact DM halos. If DM is not collisionless but...

Paper day! Today we have our latest study on how to accurately simulate gravothermally collapsing dark matter halos on arXiv!
arxiv.org/abs/2506.06269

Today, we present the first N-body simulations of a self-interacting dark matter spike around a supermassive black hole in our paper led by V. Sabarish. https://arxiv.org/abs/2505.14779

I presented this work a few weeks ago at UCLA Dark Matter 2025: moritzfischer.world/DM25/

N-body simulations of dark matter-baryon interactions Dark matter (DM) particles can interact with particles of the Standard Model. Although there exist constraints from direct and indirect detection experiments, the dynamical evolution of astrophysical ...

Finally out! Our paper with the first N-body simulations of dark matter-baryon interactions is now on arXiv. arxiv.org/abs/2504.12393

How can we simulate realistic self-interacting dark matter models with large- and small-angle scattering? Check out the new study led by our student Cenanda Arido! https://arxiv.org/abs/2410.07175

Delighted to see that the work led by S. Yang with new constraints on velocity-dependent self-interactions of dark matter got accepted! https://arxiv.org/abs/2305.05067

Happy that our paper on numerical issues in simulations of collapsing self-interacting dark matter halos got accepted. https://arxiv.org/abs/2403.00739

It was a pleasure to discuss dark matter research at the KITP conference "Cosmic Signals of Dark Matter Physics: New Synergies"! I am happy that my talk about signatures of the angular dependence of dark matter self-interactions is available on YouTube. https://youtu.be/wmtmhLMgSG8

How does dynamical friction change when dark matter has self-interactions? Learn about it in our new paper by Laura Sagunski and myself. https://arxiv.org/abs/2405.19392

SIDM can make subhalos in galaxy clusters more compact, but in a different way than one would naively expect, as shown in our study led by A. Ragagnin, using full physics zoom-in simulations. https://arxiv.org/abs/2404.01383

Just compiled a plot of various constraints on the dark matter self-interaction cross-section for my upcoming talks.

Two and four weeks ago, two papers appeared on arXiv investigating numerical problems in N-body simulations of collapsing SIDM halos. We join them with our study explaining the causes of energy conservation errors in simulations of the late collapse phase. https://arxiv.org/abs/2403.00739

In our second paper today, led by V. Sabarish, we find that the effects of velocity-dependent self-interactions are more pronounced in the late stages of merging galaxy clusters than shortly after the first passage of the clusters through each other. https://arxiv.org/abs/2310.07769

Today on arXiv, our qualitative study of velocity-dependent self-interactions. We find that a strong velocity dependence can diversify the halo population regardless of the angular dependence of the scattering. https://arxiv.org/abs/2310.07750

I am honoured to have received the Best Paper Award from the Cluster of Excellence Quantum Universe today. https://www.qu.uni-hamburg.de/research/highlights/23-04-18-fischer.html

Our new website for our research on self-interacting dark matter is online. Check it out! https://darkium.org

Paper day! We have studied the role of the ICM in merging galaxy clusters with SIDM: 1. the presence of the ICM enhances DM-galaxy offset, 2. the position of the shock front combined with the galaxy positions could be an interesting probe of DM. https://arxiv.org/abs/2302.07882