Where: IREAP Large Conference Room, ERF 1207

Speaker: Juan Uriagereka (UMCP, Dept of Linguistics) - http://ling.umd.edu/~juan/

Abstract: Formal and generative linguistics has always assumed the manipulation of feature matrices in its operations. However, relatively little thought had been given, until the last decade or so, to how these putative matrices operate, beyond the assumption that they somehow do. This talk explicitly argues that matrix multiplication (Hadamard and Kronecker products) is a useful way to operate with linguistic matrices. Under standard linguistic assumptions (in particular "projection", the idea that a linguistic phrase of type X must immediately dominate another syntactic object of type X – e.g. a verb phrase contains a verb, a noun phrase contains a noun, etc.), this view of things predicts a number of distributional facts among phrasal dependents, which currently is not predicted in any other way. The formalism also has significant consequences for long-distance relations among phrases in syntax (e.g. conditions on question formation, ellipsis, etc.) and the study of grounding natural language on the mind/brain of speakers.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Tsevi Beatus (Dept of Physics, Cornell University) -

Abstract: Flying insects can perform a wide array of extreme aerial maneuvers with exquisite accuracy and robustness, outmaneuvering any man-made flying device. As a physical system, a flapping insect is strongly nonlinear with fast-growing mechanical instabilities that must be controlled to allow flight. Hence, similar to balancing a stick on one's fingertip, flapping flight is a delicate balancing act made possible only by ever-present, fast corrective actions. Understanding the underlying mechanisms of insect flight is a major challenge, since this graceful behavior is highly coupled to complex fluid flows and arises from the concerted operation of physiological functions across multiple length and time scales. As such, Insect flight research involves basic concepts from nonlinear dynamics, fluid mechanics, neurobiology and control theory, and has direct application to the development of small flapping robots.

Here we show how flies control their rotational degrees of freedom: yaw, pitch and roll. We focus on their body roll angle, which is unstable and most sensitive degree of freedom. We glue a magnet to each fly and apply a short magnetic pulse that rolls it in mid-air. Fast video shows that flies fully correct for perturbations of up to 〖100〗^o within 30±7ms. The roll correction maneuver consists of a stroke-amplitude asymmetry that is well described by a linear PI controller. For more aggressive perturbations, we show evidence for nonlinear and hierarchical control mechanisms. Flies respond to roll perturbations within a single wing-beat, or 5ms, making this correction reflex one of the fastest in the animal kingdom.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dr. Amit Agrawal (UMCP -NIST Nanocenter) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: Suddhasattwa Das (UMD, Dept of Mathematics) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dr. Sebastian Ahnert (Cambridge University) - http://www.tcm.phy.cam.ac.uk/~sea31/

Where: IREAP Large Conference Room, ERF 1207

Speaker: Prof. Flavio Fenton (Georgia Tech) - https://www.physics.gatech.edu/user/flavio-fenton

Where: IREAP Large Conference Room, ERF 1207

Speaker: Prof. Christine Hartzell (UMD, Dept of Aerospace Engineering) - http://www.aero.umd.edu/faculty/hartzell

Where: IREAP Large Conference Room, ERF 1207

Speaker: Prof. Peter Taborek (UC-Irvine) - http://www.physics.uci.edu/~taborek/

Abstract: Abstract: No slip boundary conditions successfully describe macroscopic flows near solids, but this boundary condition is not a law of physics, and several recent experiments have invoked large slip lengths to explain surprising results on flow through carbon nanotubes and other nanoscale flows. We will describe measurements of the mass flow rate as a function of pressure for flow through nanopipes made from single ion etch tracks 20 nm in diameter and glass tubes 200 nm in diameter. The extremely small flows involved are detected with a mass spectrometer. For classical fluids, our measurements always yield slip lengths less than 2 nm. For superfluid 4He , the flow rate has a complicated dependence on temperature and pressure which reflects the kinetics of vortex nucleation and vortex motion in the nanopipe.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dr. Manis Chaudhuri (Harvard University) - http://scholar.harvard.edu/manischaudhuri/home

Where: IREAP Large Conference Room, ERF 1207

Speaker: Juergen Kurths (Potsdam Inst. for Climate Impact and Humboldt University) - https://www.pik-potsdam.de/members/kurths

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dr. Sharon Bewick (UMD, Dept of Biology) - http://www.clfs.umd.edu/biology/faganlab/people/bewick.html

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dr. Dong Ho Wu (NRL) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: Mahesh Bandi (Okinawa Institute of Science and Technology) - https://groups.oist.jp/ciu/mahesh-m-bandi

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dan Lathrop and Ed Ott (IREAP) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: David Levermore (Dept of Mathematics, UMD) - http://www.math.umd.edu/~lvrmr/

Abstract: We develop a scattering theory for a class of eternal solutions of the Boltzmann equation posed over all space. In three spatial dimensions, each of these solutions has thirteen conserved qualities. The Boltzmann entropy has a unique minimizer with the same thirteen conserved values. This minimizer is a local MAxwellian that is also a global soution of the Botlzmann equation - a so-called global Maxwellian. We show that each of our external solutions has a streaming asymptotic state as time goes to minus- or plus-infinity. However, it does not converge to the associated gloabl Maxwellian as time goes to infinity unless it is that global Maxwellian. The Blotzmann entropy decreases as time increases, but does not decrease to its minimum as time goes to infinity. Said another way, the final step in the traditional argument for the heat death of the universe is not valid.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Andrea Bertozzi (UCLA, Dept of Mathematics) - http://www.math.ucla.edu/~bertozzi/

Where: IREAP Large Conference Room, ERF 1207

Speaker: Jeff Demers and Ayoti Patra (UMD, IPST) -

Abstract: Jeff Demers

Universal energy diffusion in a quivering billiard

Abstract: In this talk, I will discuss a particular limit of time-dependent billiard motion called "the quivering limit," and the resulting billiard systems called "quivering billiards." I will show that the quivering limit is well-defined and physically interesting, yet allows for analytic calculations of physical quantities such as correlations and time-dependent energy distributions. As time allows, I will share some interesting and surprising features of quivering billiards; namely that time-dependent billiards behave universally in the quivering limit, regardless of billiard shape or dimensionality, and that the insights gained through studying quivering billiards resolve some long standing problems in the time-dependent billiard literature. I will also mention some exciting ongoing projects which employ quivering billiards to address current topics of interest in non-equilibrium thermodynamics and statistical mechanics at the nanoscale.

Ayoti Patra

Shortcuts to adiabaticity for a quantum tilted piston

Abstract: Shortcuts to Adiabaticity are techniques used to control a system evolving under a rapidly changing Hamiltonian. I will start by describing one such technique, known as 'Transitionless Quantum Driving', in which a quantum system is subjected to evolve under a composite Hamiltonian H_0(t) + H_{CD}(t), such that it remains in a given energy eigenstate of H_0(t) throughout the evolution. I will describe a method to obtain the term H_{CD}(t) starting from an analogous problem of 'classical dissipationless driving'. I will illustrate this method using the example of a tilted piston.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Steve Anlage (Depts of Physics and ECE, UMD) - http://anlage.umd.edu/

Where: IREAP Large Conference Room, ERF 1207

Speaker: Michael E. Fisher (IPST, UMD) - http://www.ipst.umd.edu/researchandfaculty/xpectnil.php

Abstract: The first half raises queries arising from my 1968-70 work (PRL with Jim Langer) to "explain" the Reppy experiments. The main observation/theory-query - apart from the "critical velocity" following the Superfluid Density and so vanishing with the 2/3 power law - is the logarithmic decay of the superflow with time. The second part is devoted to Daniel Lathrop's experiments (originally with Katepalli Sreenivasan) and especially the GPEqn with Cecilia Rorai. There I will describe our "discovery" that the actual vortex intersection takes place in a Plane of Reconnection.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Guenter Radons (Technical University Chemnitz, Institute of Physics, Germany) - https://www.tu-chemnitz.de/physik/KSND/radons/

Abstract: For randomly accelerated particles we recently detected and analyzed in detail the phenomenon of weak ergodicity breaking (WEB), i.e. the inequivalence of ensemble- and time-averaged squared displacements. These results, including their aging time dependence, are relevant for anomalous chaotic diffusion in Hamiltonian systems, for passive tracer transport in turbulent flows, and many other systems showing momentum diffusion. After explaining the basic concepts and results, I introduce models with a similar statistical behavior, namely the integrated random excursion model, space-time correlated Lévy walks, and space-time correlated Lévy flights. A comparison of the WEB related properties of these models reveals surprising differences, although, for equivalent parameters, one would naively expect equivalent results for the mean squared displacements. Our findings are relevant for distinguishing possible models for the anomalous diffusion occurring in experimental situations.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Joe Hart and Kanika Bansal (UMD) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: Chris Jarzynski (University of Maryland, Department of Chemistry and Biochemistry ) -

Abstract: diabatic invariants are important in classical mechanics, quantum mechanics and thermodynamics. I will consider the following classical problem in one degree of freedom. Given a time dependent Hamiltonian H(q,p,t), we wish to construct an auxiliary potential U(q,t) with the property that all trajectories launched from a specified initial energy shell E_0 of H(q,p,0), and subsequently evolving under H(q,p,t) + U(q,t), will end on a single energy shell E_tau of H(q,p,tau). By Liouville’s theorem these two shells share the same action. In this manner the auxiliary potential U(q,t) steers the trajectories so that the final action is exactly the same as the initial action, for every trajectory and for arbitrarily fast time-dependence of H(q,p,t). I will present a simple solution to this problem and will discuss its relationship to analogous solutions for quantum systems.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Juan Restrepo (University of Colorado, Department of Applied Mathematics) - http://amath.colorado.edu/faculty/juanga/Juan_G._Restrepo.html

Where: IREAP Large Conference Room, ERF 1207

Speaker: Denys Bondar (Princeton University, Department of Chemistry) -

Abstract: In this talk, I will provide an answer to the question: “What kind of observations and assumptions are minimally needed to formulate a physical theory?” Our answer to this question leads to the new systematic approach of Operational Dynamical Modeling (ODM), which allows to deduce equations of motions from time evolution of observables. Using ODM, we are not only able to re-derive well-known physical theories (such as the Schrodinger and classical Liouville equations), but also infer novel physical dynamics (and solve open problems) in the realm of non-equilibrium quantum statistical mechanics.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Ken Showalter (West Virginia University, Department of Chemistry) -

Abstract: We have studied large, heterogeneous populations of discrete chemical oscillators (~100,000) to characterize two different types of density-dependent transitions to synchronized behavior, a gradual Kuramoto synchronization and a sudden quorum sensing synchronization. We also describe the formation of phase clusters, where each cluster has the same frequency but is phase shifted with respect to other clusters, giving rise to a global signal that is more complex than that of the individual oscillators. Finally, we describe experimental and modeling studies of chimera states and their relation to other synchronization states in populations of coupled chemical oscillators.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Henry Abarbanel (UC San Diego, Department of Physics ) -

Abstract: This is about how to do 4DVar, as the meteorologists call it--with some confidence one has found the lowest minimum for the cost function--and, methods for evaluating the corrections to this approximation. Many more subtle details which I would be pleased to get your views about as well.

Where: IREAP Large Conference Room, ERF 1207

Speaker: Dietmar Plenz (NIH, National Institute of Mental Health) -

Where: IREAP Large Conference Room, ERF 1207

Speaker: Padi Boyd (NASA, Goddard) -

Abstract: Abstract: The Time Domain Astronomy (TDA) renaissance is already well underway. The K2 mission is amassing an impressive collection of high precision, evenly sampled, long time baseline optical observations on par with those from the original Kepler mission, and high-energy space-based all-sky monitors continue to watch virtually every bright X-ray source in the sky. These facilities monitor accreting compact binaries: some show high-amplitude “superorbital” variability, on timescales longer than the orbital timescale, sometimes ascribed to the motion of a warped, precessing accretion disk. Warped accretion disks appear to be important in many astrophysical environments, from planet formation to accreting supermassive black holes at the hearts of active galaxies. But even the most well-behaved X-ray binary sources show surprising deviations from strictly periodic variability. This talk will explore the variety of non-periodic variations seen in these systems, and some of the analysis tools used beyond traditional power spectral analysis, which is often insufficient. Such tools include phase-space embedding and topological analysis used by some in the nonlinear dynamics community. As the time baseline grows, these tools become more powerful, giving us hints about what drives such variability. I hope to get you thinking and commenting about whether a recently proposed accretion disk dynamo model might be able to explain the double-well-potential-like behavior seen in some systems; thus taking the next steps in understanding the dynamics of accretion disks.