Daniela Kraft
Leiden University, The Netherlands

Abstract

Synthetic microswimmers constitute a new class of nonequilibrium model systems that hold great promise for applications and understanding the behavior of biological microswimmers. A simple experimental realization of such microswimmers are spheres half coated with platinum, that propel themselves autonomously in the presence of hydrogen peroxide. These synthetic swimmers have a strong affinity for surfaces, but little is known about how surfaces affect their behavior. In this talk, I will demonstrate that the choice of the substrate material has a strong influence on the microswimmer speed through slippage [1]. Then, using a new height analysis approach, I will show that the microswimmer-wall separation is surprisingly robust for a range of salt concentrations, swimmer surface charges, and swimmer sizes [2]. Finally, we find that swimmers speed up and synchronize when they move at close distances . These striking, activity-induced findings have furthermore important implications for the still-debated propulsion mechanism. 

References

[1] Ketzetzi, de Graaf, Doherty, Kraft, PRL 124, 048002 (2020)

[2] Ketzetzi, de Graaf, Kraft, PRL (accepted, 2020) & arXiv 2006.06384 [cond-mat.soft]
 

 

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Deborah Harris
York University
Senior Scientist, Fermilab

Abstract

Neutrinos are fascinating particles because they were created less than a second after the Big Bang and hence are one of the few particles to provide a window into the creation of the universe.  There are now a billion times more neutrinos than the particles that make up normal matter, yet we know little about neutrinos because they rarely interact.  We know neutrinos come in three different kinds, and they transform (or oscillate) from one kind to another (a discovery that received the 2015 Physics Nobel Prize).  The fact that neutrinos have mass and oscillate means that we can learn a great deal about them by studying what are effectively interference patterns that arise after neutrinos propagate over hundreds of kilometers.  The DUNE experiment will measure these interference patterns over a broad neutrino energy range after neutrinos have propagated 1300km.  In addition, DUNE will use a detector technology that provides exquisite detail about the interactions that make up the interference pattern.  This talk will present the current status of oscillation measurements and of recent progress on preparations for DUNE.

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Sabetta Matsumoto
Assistant Professor, Georgia Institute of Technology-School of Physics

Abstract

Imagine a 1D curve, then use it to fill a 2D manifold that covers an arbitrary 3D object – this computationally intensive materials challenge has been realized in the ancient technology known as knitting. This process for making functional materials 2D materials from 1D portable cloth dates back to prehistory, with the oldest known examples dating from the 11th century BCE. Knitted textiles are ubiquitous as they are easy and cheap to create, lightweight, portable, flexible and stretchy. As with many functional materials, the key to knitting’s extraordinary properties lies in its microstructure.

At the 1D level, knits are composed of an interlocking series of slip knots. At the most basic level there is only one manipulation that creates a knitted stitch – pulling a loop of yarn through another loop. However, there exist hundreds of books with thousands of patterns of stitches with seemingly unbounded complexity.

The topology of knitted stitches has a profound impact on the geometry and elasticity of the resulting fabric. This puts a new spin on additive manufacturing – not only can stitch pattern control the local and global geometry of a textile, but the creation process encodes mechanical properties within the material itself. Unlike standard additive manufacturing techniques, the innate properties of the yarn and the stitch microstructure has a direct effect on the global geometric and mechanical outcome of knitted fabrics.

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physics.gatech.edu/user/elisabetta-matsumoto

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Paul Charbonneau
Département de Physique, Université de Montréal

Abstract

A snowflake, a lichen, and a solar flare; my first is a crystal whose structure is set by molecular interactions at the nanometer scale; my second is a symbiotic biological organism of centimeter scale shaped by strong physical constraints; my third is an energy release event occurring in a magnetohydrodynamical system of scales reaching a million kilometers. What could these three systems possibly have in common ? In this talk I will discuss a physical modelling paradigm whereby such natural complex systems and phenomena emerge from a great many simple dynamical elements interacting locally with one another at scales much smaller than the global scale of the system. Complexity thus emerges from simplicity! However this cannot be viewed as a disguised form of reductionism, because here even perfect knowledge of microscopic dynamics cannot be used to predict macroscopic behaviour, as it does in statistical thermodynamics.

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Prof. Kent Moore
University of Toronto Mississauga

gwk.moore@utoronto.ca

Abstract

Professor Moore has for over 25 years taken the earth’s temperature and done in depth analysis on how and why it is changing. He has flown through winter storms in the Arctic, climbed some of our highest peaks, measured Artic sea ice and examined ice cores. He would like to share his findings and thoughts, so you can better understand the physics behind our changing climate and what it means to you.

Short bio

Professor Moore has a Ph.D. in Geophysical Fluid Dynamics from Princeton Univ. He is a Professor of Physics at the Univ. of Toronto, the Vice-Principal Research at the Univ. of Toronto Mississauga and a recent Fulbright Visiting Chair in Arctic Studies at the Univ. of Washington. Professor Moore’s research interests include: geophysical fluid dynamics, polar meteorology, observational studies of high latitude air-sea-ice interactions, physical oceanography, paleoclimatology and high-altitude physiology. Prof. Moore has published over 170 research papers in the peer-reviewed literature Among the journals that Professor Moore has published in include: Science, Nature, Nature Climate Change, the New England Journal of Medicine, the Journal of Climate, the Journal of Hydrometeorology, Geophysical Research Letters, the British Medical Journal, Progress in Oceanography, Deep Sea Research and the Quarterly Journal of the Royal Meteorological Society. Prof. Moore has played a leadership role in a number of national and international research collaborations aimed at improving our understanding of how the ocean and atmosphere exchange heat, moisture and momentum including the Canadian Atlantic Storms Program, the Beaufort and Arctic Storms Experiment, the Canadian GEWEX (Global Energy and Water Cycle Experiment) Program, the Labrador Sea Deep Ocean Convection Experiment, the Greenland Flow Distortion Experiment, the Storms of the Arctic Experiment and the Iceland-Greenland Sea Project.

 

Nir Rotenberg
University of Copenhagen

Abstract

Quantum photonics is no longer just an exploration of fundamental physical laws; we now also use quantum effects to construct devices to, for example, produce single photon sources or perform quantum measurement. That is, we are in the process of bringing the research from the lab and into the marketplace. This process, however, is in its infancy, and the type and power of the resultant devices still strongly depends on the way in which we can generate and manipulate quantum states.

In this talk, I focus on some of our recent results in observing and controlling nonlinear light-matter interactions using solid-state emitters coupled to nanophotonic waveguides. I begin by explaining the passive nonlinearities of these emitter-waveguide systems, and how these can form the basis for a photon sorter: a device that can enable a deterministic Bell-state measurement, and thus forms a key component of a long-range quantum network. I then turn to our recent efforts to actively control these quantum nonlinear interactions, and bring multicolor nonlinear optics to the single-photon level, thereby opening routes towards active quantum devices such as photon switches, routers, or even reconfigurable networks.

 

Rachel Friesen
University of Toronto

Abstract

The conversion of gas into stars is a key process driving the evolution of structures in the universe. Recent surveys of dust continuum emission of Galactic star-forming regions have revealed the ubiquity of filamentary structures within molecular clouds, raising the tantalizing possibility that the star formation efficiency is strongly dependent on how these dense filaments form and evolve. I will show how the combined analysis of gas dynamics and chemistry in star-forming regions is critical to understand filamentary mass accretion, stability, and fragmentation. Consequently, large-scale surveys of molecular lines that trace dense, star-forming gas are sorely needed. Filling this gap, I will present results from the Green Bank Ammonia Survey, a Large Program on the 100m Green Bank Telescope that has mapped the dense molecular gas of all the major star-forming molecular clouds within 500 pc. Finally, I will discuss how new and upcoming facilities will enable tests of star formation theory over the next decade from stellar cluster to protostellar disk scales.

 

King Yan Fong
University of California, Berkeley

Abstract

Scientists’ vision of building miniaturized machines atom-by-atom has inspired today’s micro- and nano-scale devices such as photonic, electronic, mechanical, and microfluidic systems, which have now become an integral part of our modern life. Nano-systems allows integration of different systems onto same platform to realize cross-functional devices. The enhanced light-matter interaction at nano-scale also allows light to couple with mechanical motion to achieve optical sensing and control with unprecedented bandwidth and sensitivity. Operation of nano-devices in quantum regime further opens up new prospects in sensing and information processing applications.

In this seminar, I will talk about three topics of nano-opto-mechanical systems in areas spanning from fundamental studies to practical applications. I will show you how heat transfer through quantum vacuum can be observed using nano-mechanical sensor [1], how the challenge of mechanical sensing in fluidic environment can be tackled [2,3], and how scaling of nano-system down to single atomic layer allows realization of new device functionality [4]. In the end, I will share with you my view of where further scaling and integration of nano-systems may lead to.

[1] K. Y. Fong, et al., Nature 576, 243 (2019).
[2] K. Y. Fong, et al., Nano Lett. 15, 6116 (2015).
[3] K. Y. Fong, et al., Nano Lett. 19, 3716 (2019).
[4] H.-K. Li*, Fong*, et al., Nat. Photon. 13, 397 (2019). *equal contribution

 

Nahee Park
University of Wisconsin-Madison

Abstract

In 1912, Austrian physicist Victor Hess discovered, with a high-altitude balloon experiment, a flux of highly energetic particles coming from outer space - for which he won the Nobel Prize. Now known as cosmic rays, these particles have been the topic of numerous studies ever since their discovery. Because of their deflection by magnetic fields and their interactions with particles and radiation in interstellar and intergalactic space, cosmic rays arriving at Earth carry little information about their sources. Instead, observations of the neutral particles, such as gamma rays and neutrinos, produced during the interactions experienced by cosmic rays have been studied in order to search for their elusive source sites. Observations of neutrinos provide a key element in these studies, as neutrinos can probe source environments that, due to their distance or obscuration, are inaccessible to gamma-ray observatories. Recently, the IceCube experiment located at the South Pole has revealed the first neutrino view of the cosmos, opening a new window to explore the sources of high-energy cosmic rays in our Universe. I will highlight the role that these high-energy neutrino observations play in the emerging discipline of multi-messenger astrophysics, focusing on the recent IceCube neutrino alert from a flaring blazar, TXS 0506+056. I will also discuss what we expect to learn in the future with the next-generation neutrino observatory, IceCube-Gen2, and summarize how these observations will allow us to explore fundamental physics, including searches for decaying dark matter throughout the Universe.

 

Alexander Tait
NIST: National Institute of Standards and Technology

Abstract

At low-temperature, silicon can be made to emit light, and superconducting wires can detect single photons. When integrated with silicon photonic waveguides, this combination of sources and detectors forms the basis of an emerging platform for cryogenic silicon photonics. A new photonic integrated circuit platform could potentially impact current approaches to quantum measurement, communication, and computing. The extent of these potentials depends on further development of on-chip silicon light sources. There are two frontiers: high-power sources for nonlinear optics, and very low-power (single-photon) sources for quantum optics.

Silicon photonics has opened possibilities for new concepts in optical information science - this is also true at room temperature. Neuromorphic silicon photonics has pushed the bounds of machine learning performance. As with any revolutionary computing technology, neuromorphic photonics could have unforeseen and fascinating other applications, perhaps most dramatically in autonomous analysis and control of ultrafast phenomena.

This talk will summarize recent progress in neuromorphic silicon photonics and touch on some current research frontiers. I will give an introduction to cryogenic silicon optoelectronics and describe how these physics can connect to information processing. Special attention will be given to current progress and future directions in cryogenic all-silicon light sources.