Dynamics of Dark Matter

'Dark matter' (DM) is a dynamical hypothesis born from our inability to comprehend kinematic observations at the galaxy scale and larger using baryonic matter only. Astronomers have struggled with the implications of DM for galaxy formation and evolution for decades. Conversely, we've exploited observations and cosmological simulations to constrain the DM hypothesis. The many failures in our standard cosmongony have led to a long list of 'crises' in the paradigm and motivated some to abandon Newtonian gravity. This talk will address the question: why are we still at this 45 years later? I will attempt to convince you from first principles and examples that the answer is rooted in the complex nature of dynamics itself. Galaxies are the limit of many-body systems with an infinite degrees of freedom. I will set the stage with a review of dynamics in this infinite limit and motivate how and why correct simulations of DM dynamics is hard. I will then move on to real-world examples of interactions, the mystery of barred galaxies, and a sobering surprise from the details of halo dynamics itself. I will end by proposing a framework for making more progress.

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During the Higgs colloquium on Friday, April 21 2023, an image in breach of the University of Edinburgh's Dignity and Respect Policy has been inadvertently displayed. We apologise for any harm this incident might have caused. We encourage to raise any concern to the attention of the School of Physics and Astronomy's Equality Diversity & Inclusion Committee.