Neck Rupture and Scission Neutrons in Nuclear Fission

Just before a nucleus fissions a neck is formed between the emerging fission fragments. It is widely accepted that this neck undergoes a rather violent rupture, despite no direct experimental evidence, and only a few contentious theoretical treatments of this fission stage were ever performed in the more than eight decades since nuclear fission was experimentally observed by Hahn and Strassmann and described by Meitner and Frisch in 1939. In the same year, Bohr and Wheeler conjectured that the fission of the nuclear liquid drop would likely be accompanied by the rapid formation of tiny droplets, later identified with either scission neutrons or other ternary fission fragments, a process which has not yet been discussed in a fully quantum many-body framework. The main difficulty in addressing both of these stages of nuclear fission is both are highly non-equilibrium processes. Here we will present the first fully microscopic characterization of the scission mechanism, along with the spectrum and the spatial distribution of scission neutrons, and some upper limit estimates for the emission of charged particles.Comment: 5 pages, 4 figure

Measures of complexity and entanglement in fermionic many-body systems

We discuss the properties of the canonical wave functions, which are needed in order to evaluate the quantum Boltzmann one-body and the Shannon entropies, which characterize the degree of complexity and entanglement of many-body wave functions. We illustrate these aspects in the particular case of a complex non-equilibrium process, the induced nuclear fission described within a real-time Density Functional Theory framework.Comment: 10 pages, 7 figures, significant change

Simulation of Bacterial Motion in Sterically Complex Environments

Project files are comprised of 1 page pdf and presentation recording in mp4 format.Many species of bacteria navigate complex and heterogeneous environments to search for metabolic resources and avoid toxins. Common among such complexities is steric structure – solid objects whose surface curvature alters bacterial trajectories upon impact. In previous experiments, we characterized scattering of bacteria from vertical pillars of different radii, which provides the basis for understanding how impact with a solid, curved object alters bacterial motion. However, it remains poorly understood how multiple interactions affect bacterial trajectories and whether distinct object curvatures or length-scales of separation between steric objects have qualitatively distinct effects on bacterial motion. We address this question using agent-based computer simulations of cells moving within 2D environments. Each environment presents simulated cells with steric objects (i.e. circular pillars) of radius 8.3µm and a controlled separation between pillars of µm, where is a parameter of the simulation. Cells then diffuse through this environment, scattering with pillars they encounter. By measuring the mean squared displacement (MSD) of the ensemble of trajectories in time for different values of , we are able to quantify precisely how the length-scales of separation between steric structures affect bacterial trajectories. These MSD measurements will also allow us to compare our results with future experimental work. Ultimately, we hope that our results may contribute to a more realistic model of the behavior of motile cells in natural environments such as soils or a mammalian gut.CURE SUR