Colloquium by Matt Caplan, Illinois State
Neutron star crusts are weird. They are fully ionized plasmas of nuclei at densities reaching 1014 g/cm3, but under such high pressure that they freeze into a crystal solid. The elastic properties of this solid are especially important for understanding crust breaking and transients in magnetar outbursts and starquakes, but this material cannot break like terrestrial solids due to the high pressure suppressing the formation of fractures and voids. Fortunately, large scale molecular dynamics simulations make it possible to study breaking, plastic flow, and other behavior beyond linear elasticity. I will present our new molecular dynamics simulations demonstrating that neutron star crusts likely have very simple elastic-perfectly plastic rheology, with many strong analogs to terrestrial materials. If perfect crusts experience brittle failure and flow plastically before reannealing, it's possible that neutron star crusts experience 'cycling' with implications for magnetar outbursts.
Bio: Matt Caplan is an Associate Professor at Illinois State University and a Visiting Professor at the University of Illinois Urbana-Champaign. He was a CITA National Fellow at McGill and his PhD from Indiana University won the 2018 APS Dissertation Award in Nuclear Physics. Dr. Caplan works on high energy density matter in white dwarfs, neutron stars, and accreting black holes. Beyond academia, Dr. Caplan is a scriptwriter for the YouTube channels, Kurzgesagt and PBS Space Time, having contributed to over 100 videos with combined view counts of a billion. Also active in arms control, he was an inaugural fellow of the Physicists Coalition for Nuclear Threat Reduction and is the creator and host of the NPR podcast, Twelve Thousand Bombs.
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Host: Anirudh Patel