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.

 

Ziqing Hong
Northwestern University

Abstract

Dark matter is a hypothetical form of matter that, if it exists, may account for more than a quarter of the energy density of our universe. Despite the variety of astrophysical evidence pointing to its existence, the direct interaction of dark matter in a terrestrial detector is yet to be observed. The Super Cryogenic Dark Matter Search (SuperCDMS) experiment tries to observe a dark matter signal in silicon and germanium detectors operated around 50 miliKelvin. In this talk, I will discuss the status of the next generation SuperCDMS experiment, the recent results with an eV-resolution gram-scale prototype detector, and the future plan with this technology.

 

Dr. Shawn Westerdale
Princeton University

Abstract

Dark matter comprises 27% of the energy density of the universe -- about 5 times more than baryonic matter. Despite this abundance, its nature remains a complete mystery. While several theories predict different dark matter candidates, no experimental evidence to date can confirm any of them. Many experimental efforts are currently underway, aiming to directly detect some of the most promising candidates — a challenge akin to finding a needle in a haystack. To accomplish this, large detectors can be built deep underground, where backgrounds are greatly reduced. In this colloquium, I will review techniques used to search for dark matter, focusing on the DarkSide-50 and DEAP-3600 liquid argon-based detectors. I will discuss significant advances that have been made in reducing backgrounds for these dark matter searches and in improving liquid argon detector technology, paving the way for a future set of detectors to probe low- and high-mass candidates. 

Dr. Westerdale is a candidate for the tenure-track faculty position in Particle Astrophysics.  Faculty are encouraged to meet with Dr. Westerdale during his 2 days of visits.  Students and postdocs are welcome to join for a catered lunch immediately following the colloquium in Stirling 201.

 

Dr. Laurie Barge
Research Scientist in Astrobiology at the NASA Jet Propulsion Laboratory

Abstract

To search for biology on other worlds, it is important to have working definitions of what constitutes “life” and “non-life”. However, the distinction between biotic and abiotic is often unclear, since we are still learning about the limits of life, and also because abiotic systems can become highly complex when devoid of biological influence. Although Earth provides a variety of examples of what biology can look like, examples of the critical steps between abiotic and biotic systems are lacking because the prevalence of life on our planet has contaminated / erased its record of prebiotic conditions. However, prebiotic chemistry may still be a current or formerly active process on other worlds with detected chemical gradients and organics, such as Enceladus, Ceres, or Mars. I will discuss how astrobiologists approach the search for life on other planets, and will describe some of the difficulties in distinguishing living and non-living systems. In particular I will share some of our lab work on simulating gradients in hydrothermal vents that could support life or its origin, and prebiotic chemistry experiments that aim to bridge the gap between geochemistry and the emergence of biochemistry.

Bio

Dr. Laurie Barge is a Research Scientist in Astrobiology at the NASA Jet Propulsion Laboratory. She co-leads the JPL Origins and Habitability Laboratory which studies the origin of life and how life can be detected on other planets, and she is the Investigation Scientist for the HiRISE instrument on NASA’s Mars Reconnaissance Orbiter (MRO). Dr. Barge’s research interests include the emergence of life on Earth, and organic chemistry on Mars and ocean worlds such as Jupiter’s moon Europa and Saturn’s moon Enceladus. She is also interested in hydrothermal vents as planetary analogs, and is the science lead for an underwater laser divebot that will be deployed to a vent in the Pacific in 2020. Dr. Barge received her Bachelor’s degree (2004) in Astronomy and Astrophysics from Villanova University, and her Ph.D. (2009) in Geological Sciences from the University of Southern California. After graduate school she was a Caltech postdoc and then NASA Astrobiology Institute postdoctoral fellow. For her astrobiology research Barge has received the JPL Lew Allen Award, the NASA Early Career Public Achievement Medal, and the Presidential Early Career Award for Scientists and Engineers.

 

Szymon Manecki
SNOLAB

Abstract

Our World is a wealthy mine of fundamental properties waiting to be explored. Two of the most intriguing mysteries are the dominance of matter over anti-matter, as well as the nature of dark matter in the Universe. Canada, with SNOLAB and its partners are at the forefront of making these discoveries in the upcoming decades. The SNO+ experiment is soon going to begin the search for neutrinoless double beta decay, known as one of the most promising probes to study the matter asymmetry in the Universe. ARGO on the other hand, is a concept for a future large-scale liquid-argon detector. In exploring the unknown nature of dark matter, ARGO will search for its possible direct interactions with ordinary matter with unprecedented sensitivity.

In this colloquium, I will present the status, development and prospects for these two projects. I will also highlight their competitiveness and complementarity in the field.

 

Orad Reshef
University of Ottawa, Ontario

Abstract

The refractive index is the single defining quantity for determining the behaviour of light propagation in a medium. Recent advances by the metamaterials community have resulted in fine control over this value in both composite and bulk materials, tuning the index to negative values and even down to zero [1]. These exotic materials exhibit extreme and counter-intuitive properties, including infinite phase velocities and seemingly diverging optical nonlinearities.

In my talk, I will first discuss the recent progress in developing monolithic zero-index metamaterials in the standard silicon-on-insulator platform [2], and how we used this material to produce and directly image light waves with infinite wavelengths at optical frequencies [3]. I will then present our recent experiments exploiting the giant ultrafast nonlinearities of another low-index material, indium tin oxide, and how this class of materials enters a non-perturbative regime of nonlinear optics [4]. Our work has important implications for the fundamental understanding of nonlinear optical phenomena and enables novel applications in ultra-thin active photonics devices.

Bio

Dr. Orad Reshef is working in nanophotonics, metamaterials and nonlinear optics. After completing a bachelor’s degree with First Class Honours in Physics at McGill University in Montreal, he joined Prof. Eric Mazur at Harvard University to pursue his doctoral studies. There, he worked on photonic titanium dioxide, integrated zero-index metamaterials, and their applications in nonlinear optics. Currently, Orad is a Banting postdoctoral fellow under Robert Boyd in the CERC group at the University of Ottawa, where he is working on nonlinear optics in epsilon-near-zero (ENZ) materials, high-Q metasurfaces based on surface lattice resonances, and nonlocal metamaterials. He is interested in scalable integrated photonic devices, and on engineering nonlinear interactions and devices that are not typically found in nature by structuring materials on the nanoscale. More information on Orad can be found online on his portfolio website: reshef.ca

Laurence Perreault Levasseur
University of Montreal

Abstract

Despite the remarkable success of the standard model of cosmology, the inflationary lambda CDM (cold dark matter) model, at predicting the observed structure of the universe over many scales, very little is known about the fundamental nature of its principal constituents: the inflationary field(s), dark matter, and dark energy. In this talk, I will give a brief overview of the successes of the inflationary lambda CDM model and discuss how, in the coming years, new surveys and telescopes will provide an opportunity to probe these unknown components. These surveys will produce unprecedented volumes of data, the analysis of which can shed light on the equation of state of dark energy, the particle nature of dark matter, and the nature of the inflation field. The analysis of this data using traditional methods, however, is entirely impractical. I will share my recent works in developing machine learning tools for cosmological data analysis and discuss how they can allow us to overcome some of the most important computational challenges for the data analysis of the next generation of sky surveys.