Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D08: GSNP Student and Postdoc Speaker and Thesis Awards, Heineman Prize, Oppenheim AwardFocus Prize/Award Recordings Available Undergrad Friendly
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Sponsoring Units: GSNP Chair: Tom Witten, University of Chicago Room: McCormick Place W-179B |
Monday, March 14, 2022 3:00PM - 3:36PM |
D08.00001: Collective dynamics on networks: Synchrony, disorder, and chimeras Invited Speaker: Yuanzhao Zhang When nonlinear dynamical components interact through complex networks, interesting collective behaviors can emerge. A natural example is synchronization, in which system-level coherence spontaneously emerge from decentralized interactions. A large body of literature has focused on the emergence of global synchrony among identical components, generating important insights such as how network structures influence a system's ability to synchronize. In this talk, I will explore two extensions of this paradigm: 1) What happens when the components are allowed to be different? Would introducing disorder always impede synchronization? 2) What new phenomena will we encounter when components are allowed to behave differently, as manifested by partial synchrony and chimeras? |
Monday, March 14, 2022 3:36PM - 3:48PM |
D08.00002: Tension-Controlled Collective Dynamics in Active Solids Paul Baconnier, Dor Shohat, Olivier Dauchot Navigating amongst diverse functionalities is a major goal of metamaterial design, with applications in various fields, from architecture, to soft robotics. Multifunctional materials are usually actuated from an external source of work, which allows for a good control of the targeted functions. The recent finding of selective and collective actuation in active solids, namely solids embedded with active units, opens the path towards autonomous actuation. This however immediately raises the question of its control. Here we show how mechanical tension can serve as a general mechanism for switching between different collective dynamics in active solids. We combine the experimental study of a centimetric model active solids, numerical study of an agent based model and theoretical arguments to reveal how tension allows for the reversible transition between different actuation regimes. More specifically we discuss the transition from a regime dominated by the presence of infinitesimal zero mode in the vibrational spectrum of the elastic structure, to a regime dominated by tension, with purely harmonic modes. We further demonstrate that for large enough tension and activity, any linear elastic structure favors the same type of actuation regime. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D08.00003: Direct evaluation of rare events in active matter from variational path sampling Avishek Das, Benjamin Kuznets-Speck, David T Limmer Active matter is driven far-from-equilibrium due to autonomous self-propulsion at the scale of individual particles. Sampling rare trajectories and computing their rates in active systems is complicated by the breaking of detailed balance. Using tools from trajectory reweighting and reinforcement learning, we have developed a novel numerical algorithm called Variational Path Sampling(VPS) that uses optimal control forces to directly generate uncorrelated reactive trajectories and compute exact rate estimates in arbitrary out-of-equilibrium systems. VPS optimizes a control force to render rare fluctuations as typical, by using a variational principle arising from a ratio of path partition functions. We have applied VPS to sample rare conformational fluctuations and compute the rate of isomerization of a passive solute dimer in a dense active bath. We find significant rate enhancement with increasing self-propulsion of the active bath, resulting from driven collisions of motile bath particles with the cross-section of the passive particles. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D08.00004: Energy diffusion and prethermalization in chaotic billiards under rapid periodic driving Wade D Hodson In this talk, I will discuss energy absorption for a chaotic billiard particle subject to a rapid, periodic driving force, with driving frequency ω. The energy dynamics of this particle can be described as a process of diffusion in energy space, wherein the particle's energy probability distribution shifts and spreads according to a Fokker-Planck equation. This model has several interesting features, including a statistical bias towards energy growth, and an energy absorption rate which is suppressed by a factor of 1/ω2. I will briefly summarize the derivation of this model, and then present explicit expressions for the associated rates of energy absorption and diffusion. I will also present numerical simulations which corroborate the energy diffusion description. Finally, I will frame these results as a case study of the phenomenon of prethermalization, and argue that the billiard model may offer insight into certain prethermal many-body interacting systems, both classical and quantum. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D08.00005: Boosting engine performance with Bose-Einstein condensation Nathan M Myers, Francisco J Peña, Oscar Negrete, Patricio Vargas, Gabriele De Chiara, Sebastian Deffner At low-temperatures a gas of bosons will undergo a phase transition into a quantum state of matter known as a Bose-Einstein condensate (BEC), in which a large fraction of the particles will occupy the ground state simultaneously. We explore the performance of an endoreversible Otto cycle operating with a harmonically confined Bose gas as the working medium. We analyze the engine operation in three regimes, with the working medium in BEC phase, in the gas phase, and driven across the BEC transition during each cycle. We find that the unique properties of the BEC phase allow for enhanced engine performance, including increased power output and higher efficiency at maximum power. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D08.00006: Developmentally-driven self-assembly and dynamics of living chiral crystals Tzer Han Tan, Alexander Mietke, Junang Li, Yuchao Chen, Hugh Higinbotham, Peter J Foster, Shreyas Gokhale, Jorn Dunkel, Nikta Fakhri Active crystals are highly symmetric ordered structures that emerge from the nonequilibrium self-organization of motile objects. Here, we show that swimming starfish embryos spontaneously assemble into highly ordered rotating active crystals that span thousands of spinning organisms and persist for tens of hours. Our experiments show that the formation, dynamics, and dissolution of these living chiral crystals are controlled by the natural development of the embryos. As a function of developmental time, these crystals undergo an order-disorder transition characterized by progressive loss of translational and orientational order. Remarkably, non-reciprocal force and torque exchanges between the embryos lead to emergence of chiral waves and signatures of odd elasticity. Our work shows how autonomous morphological development at the single-embryo level can control emergent collective nonequilibrium dynamics and symmetry breaking at the macroscale. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D08.00007: Better bending measures for plates and shells Eduardo Vitral, James Hanna We present new kinematic bending measures and quadratic energies for isotropic elastic plates and shells, with certain desirable features not present in commonly employed models in soft matter. These are justified both by simple physical arguments related to the through-thickness variation in strain, and through a detailed reduction from a three-dimensional energy quadratic in stretch. The measure of plate bending is a dilation-invariant surface tensor that couples stretch and curvature in a natural extension of primitive generalized bending strains for straight rods. The extension to naturally-curved rods and shells, for which the pure stretching of a curved rest configuration is not a dilation, contrasts with previous ad hoc postulated forms. Our results provide a clean basis for simple models of low-dimensional elastic systems, and should enable more accurate probing of the structure of singularities in soft sheets and membranes. |
Monday, March 14, 2022 4:48PM - 5:24PM |
D08.00008: Heineman Prize (2022):Antti Kupiainen Invited Speaker: Antti Kupiainen TBD |
Monday, March 14, 2022 5:24PM - 6:00PM |
D08.00009: Irwin Oppenheim Award (2022): Physical limits to biological sensing Invited Speaker: Andrew Mugler Reliable sensing is crucial for cell survival, and many cellular sensors have evolved to be as precise as physically possible. Understanding these precision limits can therefore give important insights into the mechanisms and capabilities of cell sensing. First pioneered half a century ago in the context of bacterial chemotaxis, this way of viewing sensory biology has expanded to include concentration sensing, gradient sensing, mechanosensing, thermosensing, multiplexing, time-telling, and more. I will discuss this history and describe some of our own work deriving and testing new physical bounds to sensory precision, including collective sensing by groups of cells and self-guided flow sensing by cancer cells. This field reveals the fascinating physics that constrains cell behavior and suggests that cells operate at the edge of these physical bounds. |
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