Events List for the Academic Year
Event Time:
Thursday, January 16, 2025 | 10:00 am - 11:00 am
Event Location:
BRIM 311
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2025-01-16T10:00:00
2025-01-16T11:00:00
A Personal Journey from a Condensed-Matter Theorist to an Education Researcher and Practitioner: Lessons Learned
Event Information:
Trained as a condensed-matter theorist at UBC under Mona Berciu, over the past five years I have become increasingly involved in education research and practice. In fact, I've become quite an active leader in developing and promoting Meaningful Learning towards Advanced Knowledge Generators for Cultivating Creators (ML4C). In this talk, I will share the key ideas and concepts of ML4C, which are summarized in the next paragraph. I hope that in the future, some of the courses at UBC will also be taught in this way, and that the whole curriculum—even the entire program—can be redesigned according to the core ideas of ML4C. Besides the ideas and concepts, you may also see how they were developed starting from personal learning and research experiences. In fact, this process itself is an example of how advanced knowledge generators help create knowledge, although this time on teaching and learning. ML4C provides answers to the following questions: -What to teach: Advanced Knowledge Generators (AKG), such as the ways of thinking and the methods of analysis of a discipline. -How to teach: By experiencing knowledge creation. -Why teach them in this way: One needs advanced knowledge generators to be a creator, and one masters advanced knowledge generators better by experiencing them in use. -Meaningful: For me, being a teacher who can help others become creators is satisfying, while being a teacher who feeds factual, procedural, or even conceptual knowledge to students is not.
Event Location:
BRIM 311
Event Time:
Tuesday, January 14, 2025 | 9:00 am - 11:00 am
Event Location:
HENN 309
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2025-01-14T09:00:00
2025-01-14T11:00:00
Studies of Ultracold Neutron Dynamics and Systematic Effects for the TUCAN EDM Experiment
Event Information:
Abstract:
The TRIUMF Ultracold Advanced Neutron (TUCAN) Collaboration is developing a new measurement of the neutron electric dipole moment (nEDM) with the goal of improving the current best limit of dn < 1.8E-26 ecm (90% C.L.) to the level of dn < 2E-27 ecm (90% C.L.). A non-zero nEDM requires the violation of charge-parity (CP) symmetry, and so the measurement of the nEDM can shed light on unanswered questions of fundamental physics such as baryon asymmetry, the strong CP problem, and extensions of the Standard Model such as supersymmetry.
The first part of this dissertation relates to the development of a new source of ultracold neutrons (UCNs) based on the conversion of cold neutrons, produced by a dedicated spallation source, to UCNs by downscattering in superfluid 4He. This new source will enable the desired statistical reach of the experiment. Prior to the construction of the new source, a prototype source was operated at TRIUMF from 2017 to 2019, and was used to perform experiments on UCN production, storage, and transport to assist in the design of the new source. This dissertation describes the results of a subset of those experiments, relating to the production and lifetime of UCNs in superfluid 4He.
The second part relates to the design of the TUCAN EDM spectrometer, which implements Ramsey's method of separated oscillating magnetic fields to search for a shift in precession frequency associated with the presence of a non-zero nEDM in a large electric field. To achieve the desired sensitivity, the spectrometer must be designed to minimize systematic uncertainty. The calculations and simulations described here demonstrate the requirements to achieve this goal. This work is largely focused on the design of the central region of the spectrometer, which contains the UCNs and applies the electric field. This includes the development of a prototype cell and characterization of its storage properties, simulation studies of the electric fields and impact of magnetic properties, and measurements of ferromagnetic contamination in components of the central region.
Event Location:
HENN 309
Event Time:
Monday, January 13, 2025 | 4:00 pm - 5:00 pm
Event Location:
HEBB 116
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2025-01-13T16:00:00
2025-01-13T17:00:00
Building Rocky Planets
Event Information:
Abstract:
Early in our solar system’s evolution, thousands of rocky planetesimals, little planets the size of cities or continents, formed in just a few million years. Heat from the decay of a short-lived radioactive element caused melting in many planetesimals. Dense iron-nickel metal sank and formed cores in the planetesimals, surrounded by less-dense silicate mantles, the same structure that Earth and the other rocky planets have. Over the next few tens of millions of years many planetesimals crossed paths catastrophically. Colliding worlds merged and eventually formed complete rocky planets. Rocky planets are expected to have melted significantly or perhaps completely, and likely more than once each, because of the heat of these impacts. The resulting magma oceans are a clean starting point for forward modeling of planetary evolution, using the decades of lab- and field-based information on how silicate magmas solidify. How much, then, are variations in the evolution of planets due to differences in their planetesimal building blocks prior to magma ocean formation? What makes, in the end, a habitable planet? The spectrum of possible planetesimal structures and compositions motivated our successful proposal for the NASA Psyche mission, to visit the metallic asteroid (16) Psyche. I’ll present what is known and hypothesized about building rocky planets, and also about how space missions are helping to answer questions.
Bio:
Lindy Elkins-Tanton is a Foundation and Regents Professor in the School of Earth and Space Exploration. She is also the vice president of the ASU Interplanetary Initiative, and the Principal Investigator (PI) of the Psyche mission, selected in 2017 as the 14th in NASA’s Discovery program.
Her research includes theory, observation, and experiments concerning terrestrial planetary formation, magma oceans, and subsequent planetary evolution including magmatism and interactions between rocky planets and their atmospheres. She also promotes and participates in education initiatives, in particular, inquiry and exploration teaching methodologies, and leadership and team-building for scientists and engineers.
She has led four field expeditions in Siberia, as well as participated in fieldwork in the Sierra Nevada, the Cascades, Iceland, and the Faroe Islands.
Professor Elkins-Tanton received her bachelor's and master's degrees from MIT in 1987, and then spent eight years working in business, with five years spent writing business plans for young high-tech ventures. She then returned to MIT for a doctorate. She spent five years as a researcher at Brown University, followed by five years on MIT faculty, before accepting the directorship of the Department of Terrestrial Magnetism at the Carnegie Institution for Science. In 2014, she moved to the directorship at Arizona State University.
She serves on the Standing Review Board for the Europa mission, and served on the Mars panel of the Planetary Decadal Survey and on the Mars 2020 Rover Science Definition Team.
Professor Elkins-Tanton is a two-time National Academy of Sciences Kavli Frontiers of Science Fellow and served on the National Academy of Sciences Decadal Survey Mars panel. In 2008 she was awarded a five-year National Science Foundation CAREER award, and in 2009 was named Outstanding MIT Faculty Undergraduate Research Mentor. In 2010 she was awarded the Explorers Club Lowell Thomas prize. The second edition of her six-book series "The Solar System," a reference series for libraries, was published in 2010; the book "Earth," co-authored with Jeffrey Cohen, was published in 2017; and Harper Collins published her memoir, "A Portrait of the Scientist as a Young Woman" in 2022. Asteroid (8252) Elkins-Tanton and the mineral elkinstantonite were named for her.
In 2013 she was named the Astor Fellow at Oxford University, in 2016 she was named a fellow of the American Geophysical Union, and in 2018 a member of the American Academy of Arts and Sciences. In 2020 the National Academy of Sciences awarded her the Arthur L. Day Prize and Lectureship, and in 2021 she was elected to the National Academy of Sciences.
Learn more:
View her profile: https://search.asu.edu/profile/2437950
Check out her book! https://www.amazon.com/Asteroids-Meteorites-Comets-Solar-System/dp/081605195X
Watch her video: "Building a positive human space future" - Linda Elkins-Tanton interviewed by IAC TV: https://www.youtube.com/watch?v=rQdMbWbO_oA
Event Location:
HEBB 116
Event Time:
Thursday, January 9, 2025 | 10:00 am - 11:00 am
Event Location:
BRIM 311
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2025-01-09T10:00:00
2025-01-09T11:00:00
How nonlinearity distorts the evidence for photoinduced superconductivity
Event Information:
Over a decade of research has suggested that some metallic compounds can be transformed into superconductors by illuminating them with intense beams of laser light. Recently, we have shown that the experimental evidence for this effect could literally be an optical illusion produced by the high-intensity laser illumination. By examining several influential results on photoinduced superconductivity in K3C60, we have identified a fundamental flaw in their analysis that exaggerates the apparent photoinduced changes to the conductivity. When we account for this error, we find evidence that photoexcitation produces a moderate enhancement of the conductivity, but that there is no need to appeal to a photoinduced phase transition to a superconducting state. Subsequent work on K3C60 has provided quantitative support for our analysis. After discussing our reanalysis of experiments on K3C60, I will describe how this error also distorts the evidence for photoinduced superconductivity in the normal state of cuprate superconductors and in the charge-transfer salt BEDT-TTF. Finally, I will discuss how our reinterpretation raises new and interesting questions about the interaction of light with matter.
Event Location:
BRIM 311
Event Time:
Monday, January 6, 2025 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2025-01-06T16:00:00
2025-01-06T17:00:00
Finding Relativistic Stellar Explosions as Fast Optical Transients
Event Information:
Abstract:
For the last half-century, relativistic outflows accompanying the final collapse of massive stars have predominantly been detected via high-energy emission, as long-duration gamma-ray bursts (GRBs). Yet, it has long been hypothesized that GRBs are the tip of the iceberg of relativistic stellar explosions, because the conditions required to produce and detect a GRB are contrived. I will present results from a search for relativistic stellar explosions using optical time-domain surveys. The emerging zoo includes afterglows at cosmological distances with no detected GRB, supernovae with luminous X-ray and radio emission, and a mysterious class of "fast blue optical transients" with minute-timescale optical flares at supernova-like luminosities. An understanding of the origin of these events and their relation to GRBs will be enabled by upcoming time-domain surveys in other bands, including X-ray, UV, and submillimeter.
Bio:
Anna Ho's research uses telescopes located all over the world and in space to study the lives and deaths of stars and the physics of those phenomena and other energetic cosmic events. She uses wide-field surveys along with targeted observations from gamma-ray to radio wavelengths, and works to understand the physical processes governing the observed emission. She is an active member of several international collaborations, and serves as co-chair of the gamma-ray bursts working group for the ULTRASAT mission.
Learn More:
See Anna's faculty webpage from Cornell University, here: https://astro.cornell.edu/anna-yq-ho
Find her personal website here: https://annayqho.github.io/
What are long-duration gamma-ray bursts (GRBs): Imagine the Universe!
What are fast blue optical transients: Dying stars’ cocoons might explain fast blue optical transients - Northwestern Now
What is the ULTRASAT mission: Ultraviolet Transient Astronomy Satellite (ULTRASAT)
Event Location:
HENN 318
Event Time:
Thursday, December 19, 2024 | 10:00 am - 11:00 am
Event Location:
Via Zoom
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2024-12-19T10:00:00
2024-12-19T11:00:00
Ultrafast photoemission studies of bulk and exfoliated Ta2NiSe5
Event Information:
Abstract:
This thesis details the development of a 6.2 eV laser-based time- and angle-resolved photoemission spectroscopy (TR-ARPES) apparatus with micro-scale spatial resolution for the study of equilibrium and non-equilibrium properties of inhomogeneous and exfoliated samples. To demonstrate the performance of this apparatus, we spatially resolve the sample inhomogeneities giving rise to spectral broadening of the surface state of the topological insulator Bi2Se3 observed when increasing the spot-size of the 6.2 eV source incident on the sample surface.
We then explore the dynamic properties of the correlation-driven ground state of candidate excitonic insulator Ta2NiSe5. Ta2NiSe5 undergoes a semimetal-to-insulator phase transition below 328 K, accompanied by a lattice distortion from an orthorhombic-to-monoclinic structure. Because both electron-phonon and excitonic interactions can give rise to the bandgap-opening, distinguishing between the contributions of both degrees-of-freedom is theoretically and experimentally challenging. The approach presented in this thesis is to examine the change in spectral lineshape width, related to quasiparticle lifetimes, upon photodoping with a 1.55 eV pump-pulse. The experimental results are directly compared to theoretical many-body simulations, revealing that the bandgap of Ta2NiSe5 originates from predominantly electronic contributions with a much smaller, but necessary, contribution from electron-phonon coupling.
In an effort to further elucidate the electronic and lattice contribution, we exfoliate Ta2NiSe5 on Au(111) using an in-situ exfoliation method and probe the sample with our micro-ARPES apparatus. Low-dimensional studies have been shown to induce electronic states that differ from their bulk counterparts due to the confinement, and may enhance exciton binding energies due to reduced screening of the electron-hole Coulomb interaction. In this study, we explore the emergence of an in-gap state, indicating a phase transition of ultrathin Ta2NiSe5 on Au(111) to a metallic state. The study is extended to the time-domain, where we observe the metallic-like response of ultrathin Ta2NiSe5 to a high-fluence 1.55 eV pump-pulse, and directly compare to the more familiar insulating-like region of the sample where we photo-induce a semimetallic phase. Overall, this thesis work explores the tunability of the bandgap of Ta2NiSe5 through photoexcitation, dimensionality, and carrier doping, demonstrating how we can manipulate the electronic properties, and even induce phase transitions, through manipulation of the physical and electrostatic environment of the material.
Event Location:
Via Zoom
Event Time:
Thursday, December 12, 2024 | 1:00 pm - 2:00 pm
Event Location:
AMPEL building, Room 311
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2024-12-12T13:00:00
2024-12-12T14:00:00
Layer-Dependent Electronic Structure and Magnetic Transition Evolution in Two-Dimensional Ferromagnetic van der Waals Films
Event Information:
Abstract:In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry.
We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers.
We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling.
Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.:In this work, we explore what happens to a magnet when it is to only a few layers of atoms thick. To do this we grow crystals of Fe$_3$GeTe$_2$ with a technique akin to atomic spray paint, which allows for the precise control of atomic ratios to approach a nearly perfect stoichiometry.
We first demonstrate the wafer-scale synthesis of high-quality, single-crystalline FGT films with precise control over layer thickness from 1 to 10 quintuple layers (QLs). With this layer control, we are able to perform transport measurements that reveal robust ferromagnetism across all layer numbers, with drastic thickness-dependent Curie temperatures evolution from 1-4 layers.
We then employ angle-resolved photoemission (ARPES) spectroscopy and density functional theory calculations, to map the evolution of the electronic band structure with increasing layer number, identifying emergent bands and quantifying the effects of interlayer coupling.
Carrier Density measurements are then performed for all thicknesses as a function of temperature and compared to the density of states near the Fermi energy observed in ARPES. Surprisingly we observe a constant normalized carrier density per QL at the Curie temperature across different thicknesses, suggesting a universal mechanism underlying the ferromagnetic transition. We then discuss the applicability of itinerant electron-dominated or mediated mechanisms for magnetism and the unique Fe site contributions.
Event Location:
AMPEL building, Room 311
Event Time:
Thursday, December 12, 2024 | 10:00 am - 11:00 am
Event Location:
BRIM 311
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2024-12-12T10:00:00
2024-12-12T11:00:00
Majorana bound states in artificial Kitaev chains
Event Information:
The Kitaev chain model predicts the ability to engineer localized Majorana bound states: non-Abelian zero-energy excitations that are protected from local perturbations, which can be utilized for realizing robust quantum computation schemes. Recent work on InSb nanowires demonstrated that the ingredients for a minimal Kitaev chain, consisting of two sites, can be engineered by coupling quantum dots (QDs) via two second-order processes: crossed Andreev reflection and elastic co-tunnelling. To open up the path to more complex experiments, we implemented this system in a two-dimensional electron gas (2DEG). In this talk, I will detail the theoretical background and our experimental implementation of the Kitaev chain in the InSbAs 2DEG platform. I will highlight recent results obtained on a chain consisting of three quantum dots, where we find that the presence of zero energy modes on the outer QDs is correlated with a bulk excitation gap in the middle QD, demonstrating key properties of the Kitaev chain.
Event Location:
BRIM 311
Event Time:
Tuesday, December 10, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2024-12-10T16:00:00
2024-12-10T17:00:00
Special Colloquium: The NANOGrav Experiment: Current Results and Future Directions
Event Information:
Abstract:
Galaxy mergers are a standard aspect of galaxy formation and evolution, and most large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz to microhertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent evidence for a gravitational wave background, and efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers.
Bio:
Dr. Chiara Mingarelli is an Assistant Professor of Physics at Yale University and a prominent researcher in the field of gravitational wave astrophysics. Her work focuses on using pulsar timing arrays to detect nanohertz-frequency gravitational waves, particularly those generated by supermassive black hole binaries. She has held key leadership roles, including serving on NASA's Physics of the Cosmos Executive Committee and co-chairing the Gravitational Wave Science Interest Group. Dr. Mingarelli is also a Full Member of the NANOGrav collaboration, contributing to the discovery of the gravitational wave background. An advocate for diversity in science, she previously served as the Ada Lovelace Director of Diversity at the Flatiron Institute. Dr. Mingarelli has been widely recognized for her contributions, with over 100 refereed papers with 16,000 citations, and numerous grants from NASA and the National Science Foundation.
Learn More:
See Chiara's personal website here: https://www.chiaramingarelli.com/
Read her guest blog for Scientific American: https://www.scientificamerican.com/blog/guest-blog/searching-for-the-gravitational-waves-ligo-can-t-hear/
View her Yale faculty page: https://astronomy.yale.edu/people/chiara-mingarelli
Watch her videos:
Frontiers of pulsar timing array experiments: https://www.youtube.com/watch?v=uDdxcS0HeeU
Unlocking the Universe: Chiara Mingarelli on Pulsar Timing Arrays & Gravitational Waves: https://www.youtube.com/watch?v=tn--gIGKmJw
79 - NanoGRAV's Big Gravitational Wave Discovery (Ft. Chiara Mingarelli) | Why This Universe Podcast: https://www.youtube.com/watch?v=__otsacCqhY
Links:
NANOGrav Collaboration: https://nanograv.org/collaboration/overview
Pulsar Timing Array Group: https://perimeterinstitute.ca/news/international-group-pulsar-timing-arrays-announce-gravitational-wave-detection
What are gravitational waves? https://www.ligo.caltech.edu/page/what-are-gw
Flatiron Institute: https://flatironschool.com/blog/flatiron-school-relaunches-lovelace-and-ford-fellowships/
NASA's Physics of the Cosmos group: https://pcos.gsfc.nasa.gov/
Event Location:
HENN 201
Event Time:
Monday, December 9, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-12-09T16:00:00
2024-12-09T17:00:00
Entering a new, data-driven era for precision cosmology: opportunities and challenges for machine learning
Event Information:
Abstract:
Despite the remarkable success of the standard model of cosmology, the inflationary lambda CDM 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 inflaton field. The analysis of this data using traditional methods, however, is entirely impractical. I will share my recent work focused on developing machine learning tools for cosmological data analysis and discuss how these tools can help us overcome some of the most important computational challenges of analyzing data from the next generation of sky surveys.
Bio:
Laurence Perreault-Levasseur is the Canada Research Chair in Computational Cosmology and Artificial Intelligence. She is an assistant professor at Université de Montréal and an associate academic member of Mila – Quebec Artificial Intelligence Institute. Perreault-Levasseur’s research focuses on the development and application of machine learning methods to cosmology.
She is also a Visiting Scholar at the Flatiron Institute in New York City. Prior to that, she was a research fellow at their Center for Computational Astrophysics, and a KIPAC postdoctoral fellow at Stanford University.
For her PhD degree at the University of Cambridge, she worked on applications of open effective field theory methods to the formalism of inflation. She completed her BSc and MSc degrees at McGill University.
Learn More:
See her faculty webpage here: Laurence PERREAULT-LEVASSEUR - Département de physique - Université de Montréal
Read more about her research here: Laurence Perreault Levasseur – Interaction
Event Location:
HENN 318
Event Time:
Monday, December 9, 2024 | 2:30 pm - 3:30 pm
Event Location:
HENN 318
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2024-12-09T14:30:00
2024-12-09T15:30:00
PHAS Monday Tea!
Event Information:
Event Information:
Welcome everyone to Monday Tea!
This is our last Monday Tea event for 2024! Stay tuned for our 2025 schedule, which will be posted in our events calendar.
We welcome all students, staff and faculty to meet new-to-you colleagues, catch up with your physics community and to learn about current happenings in the PHAS Department.
Meet your hosts in the EDI Community Building Working Group:
Jess McIver
Adele Ruosi
Megan Bingham
Evan Goetz
Mona Berciu
Howard Li
Mandana Amiri
See you there!
Event Location:
HENN 318
Event Time:
Monday, December 9, 2024 | 12:30 pm - 2:03 pm
Event Location:
Graduate Student Centre (6371 Crescent Road), Room 203
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2024-12-09T12:30:00
2024-12-09T14:03:00
Anomalies in the cosmic microwave background
Event Information:
Abstract:
Over the past century, our understanding of the Universe has grown dramatically. Today, scientists use a model that requires just six key numbers to describe how the Universe evolved. Yet, some big mysteries remain unsolved. In my thesis, I explore two of these mysteries.
The first involves a signal that might be hidden by our movement through the Universe. Since Earth -- and our entire Galaxy -- is moving, the signals we observe are altered, via the Doppler effect. This makes it hard to separate universe-spanning signals from those caused by our motion. I investigate ways to tell them apart.
The second mystery, cosmic birefringence, rotates the light as it moves through the Universe, like light through a crystal. This could only be caused by a new type of field, like gravity or electromagnetism, and is potentially an observable caused by dark matter or dark energy.
Event Location:
Graduate Student Centre (6371 Crescent Road), Room 203
Event Time:
Sunday, December 8, 2024 | 1:15 pm - 3:00 pm
Event Location:
HEBB 100
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2024-12-08T13:15:00
2024-12-08T15:00:00
2024 Faraday Show
Event Information:
We are thrilled to announce that our annual Faraday Show will be held on Sunday December 8th, in-person, on the UBC-Vancouver campus in HEBB 100.
The Faraday Show is UBC’s annual science lecture, designed for children and all those who are ‘young at heart’. It is presented by UBC Physics & Astronomy students, faculty and staff.
This year’s theme is: "Physics in your House!". We will answer questions such as, How does the best fire alarm work? Where does static electricity come from? Why do your windows mist up in the winter? All these and more will be answered through fun demonstrations and hands-on activities!
Show schedule:
Pre-Show (table top demonstrations): 1:15PM – 1:55PM
Stage Show (stage presentations): 2:00PM – 3:00PM
This show is FREE! We ask that you please bring non-perishable food items to support Greater Vancouver Food Bank member, The Kettle Society. No RSVP required, although we recommend arriving 15-20 minutes earlier for good seats.
*Planning Tip:
Plan a day on campus! Mention “Faraday Show” and get 50% off admission at the Beaty Biodiversity Museum on Sunday December 8th, between 10am-5pm!
Event Location:
HEBB 100
Event Time:
Friday, December 6, 2024 | 1:00 pm - 2:00 pm
Event Location:
HENN 318
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2024-12-06T13:00:00
2024-12-06T14:00:00
The complex Liouville string
Event Information:
Abstract:
I will introduce the complex Liouville string, a novel and controllable model of two-dimensional quantum gravity that is defined by coupling two copies of Liouville CFT with complex conjugate central charges on the worldsheet. I will describe how by harnessing the exact solution of the worldsheet CFT we can bootstrap the string amplitudes and reveal a rich holographic duality with a double-scaled two-matrix model. Topological recursion of the matrix model leads to a recursion relation for the string amplitudes which solves the theory at the level of string perturbation theory. Finally, I will describe how the string amplitudes may be interpreted as cosmological correlators of massive particles in three-dimensional de Sitter space, integrated over the metric of future infinity. The duality with the matrix integral then establishes a novel holographic scenario for dS_3 quantum gravity. Based on work in collaboration with Lorenz Eberhardt, Beatrix Mühlmann and Victor Rodriguez.
Bio:
I am a theoretical physicist with broad interests in non-perturbative aspects of quantum field theory and quantum gravity. My research harnesses powerful non-perturbative field theory techniques together with holographic duality to bootstrap fundamental questions in quantum gravity and black hole quantum mechanics. Some of my recent work at PCTS has focused on questions related to the role of spacetime wormholes, disorder averaging and quantum chaos in holographic dualities. I am also interested in the worldsheet string theory formulation of holographic dualities.
Learn More:
See his MIT webpage here: https://physics.mit.edu/faculty/scott-collier/
View his LinkedIn page: https://www.linkedin.com/in/scott-collier-79103a201
Event Location:
HENN 318
Event Time:
Tuesday, December 3, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-12-03T16:00:00
2024-12-03T17:00:00
Entanglement Bootstrap, a perspective on quantum field theory
Event Information:
Welcome to the third talk in our new Pioneers in Theoretical Physics Colloqium Series.
On December 3rd, we present Dr. John McGreevy, professor of physics at UC San Diego.
Abstract:
I will introduce the Entanglement Bootstrap, a program to extract and understand the universal information characterizing a phase of matter starting from the entanglement structure of a piece of a single representative state. This universal information is usually packaged in the form of a quantum field theory; the program therefore provides a surprising new perspective on quantum field theory. I will discuss what we can learn about gapped topological phases and their associated topological field theories, and about quantum critical points in 1+1 dimensions and their associated conformal field theories.
Bio:
Professor McGreevy is a theoretical physicist with interests in quantum matter, string theory, and quantum field theory. His current research centers on the study and application of quantum field theory, both in condensed matter physics and in high energy physics.
Learn More:
See his personal webpage here: mcgreevy (ucsd.edu)
View his faculty profile at UC San Diego here: UC San Diego | Faculty Profile (ucsd.edu)
For more on what is Quantum Field Theory, see this Quantum Field Theory summary, from the Stanford Encyclopedia of Philosophy
Event Location:
HENN 318
Event Time:
Monday, December 2, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-12-02T16:00:00
2024-12-02T17:00:00
From Light to Insight: Discovering the Evolving Universe with Big Eyes and Big Data
Event Information:
Abstract:Have you ever wondered how we can glimpse what the Universe looked like billions of years ago or understand our place in the cosmos without ever leaving the Milky Way? This remarkable understanding comes from studying cosmic radiation—such as radio waves—that reaches us from across space. Analyzing how this radiation encodes information is key to using the Universe as a natural laboratory to address fundamental questions: How did the Universe evolve to its current state? What shaped the formation and growth of stars, galaxies, and the intricate web of plasma linking galaxies, interwoven with magnetic fields?
In recent years, large-scale sky surveys ("Big Data") conducted by modern radio telescopes ("Big Eyes") have revolutionized our ability to map the Universe across time and space.
In this talk, I will explore the state of the field in understanding the evolving Universe, with a focus on probing magnetic fields and gas using cosmic radiation. I will discuss how radiation transport in an expanding Universe—known as cosmological radiative transfer—enables us to:
• Draw meaningful comparisons between observational data and theoretical predictions, driving discoveries about cosmic magnetic fields and gas ionization on cosmological scales. • Push beyond the limits of traditional methods. • Provide valuable insights, tools, and data for frontier research and STEM outreach.
Join me in this exploration as we uncover how light transforms into profound cosmic insights, revealing the Universe’s intricate story.
Bio:
Jennifer Chan is a postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA) and the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto, supported by joint CITA and University of Toronto Faculty of Arts & Science fellowships. She earned her Ph.D. and M.Sc. in Astrophysics from University College London, and a Bachelor's in Physics from the University of Oxford. Her research focuses on investigating the origins, evolution, and properties of large-scale magnetic fields in the Universe, essential for understanding their impact on cosmic structures. She also studies cosmological reionization, the transition of the Universe from a neutral state to a highly ionized intergalactic medium, which shaped the vast cosmic web connecting galaxies. To advance these studies, she develops tools that bridge theory and observation in the fields of cosmic magnetism and reionization, such as covariant cosmological radiative transfer formalisms, which accurately model the propagation of electromagnetic radiation through different astrophysical environments in an expanding, evolving Universe.
Learn More:
See her page at the Dunlap Institute: https://www.dunlap.utoronto.ca/dunlap-people/jennifer-chan/
Read this special biography from the University of Waterloo: https://uwaterloo.ca/astrophysics-centre/events/astroseminar-jennifer-chan-person
Read this article: "Dr. Jennifer Y.H. Chan CITA Postdoctoral Fellow, is awarded the 2020 Michael Penston Thesis Prize": https://www.cita.utoronto.ca/jennifer-y-h-chan-cita-postdoctoral-fellow-awarded-2020-michael-penston-thesis-prize/
Links to sky mapping groups:
National Radio Astronomy Observatory VLA Sky Survey: https://science.nrao.edu/science/surveys/vlass
SLOAN digital Sky surveys: https://www.sdss4.org/surveys/
Large surveys at NOIRLab: https://noirlab.edu/science/data-services/surveys
Read this article: "Very Large radio surveys of the sky": https://www.pnas.org/doi/10.1073/pnas.96.9.4756
Event Location:
HENN 318
Event Time:
Monday, December 2, 2024 | 2:30 pm - 3:30 pm
Event Location:
HENN 318
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2024-12-02T14:30:00
2024-12-02T15:30:00
PHAS Monday Tea!
Event Information:
Event Information:
Welcome everyone to Monday Tea!
This is a weekly event for students, staff and faculty to meet new-to-you colleagues, catch up with your community and to learn about what's happening in the PHAS Department.
Meet your hosts in the EDI Community Building Working Group:
Jess McIver
Adele Ruosi
Megan Bingham
Evan Goetz
Mona Berciu
Howard Li
Mandana Amiri
See you there!
Event Location:
HENN 318
Event Time:
Thursday, November 28, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2024-11-28T16:00:00
2024-11-28T17:00:00
Language Models for Quantum Design
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Abstract:In the last several years, generative language models like GPT have scaled to the point where they routinely demonstrate emergence behaviour. I will demonstrate how language models can be trained on the qubit measurement data produced by today's quantum devices, and discuss how large models could help scale quantum computers in the future.
Bio:
Roger Melko is a professor at the University of Waterloo, and associate faculty at the Perimeter Institute for Theoretical Physics. He received his PhD from the University of California, Santa Barbara in 2005 and spent two years as a Wigner Fellow at Oak Ridge National Laboratory before coming back to Canada. His research involves the development of computer strategies for the theoretical study of quantum materials, atomic matter, quantum information systems, and artificial intelligence. He was the recipient of the 2016 CAP Herzberg Medal and the 2021 CAP/DCMMP Brockhouse Medal.
Learn More:
See his faculty page from University of Waterloo: Roger Melko | Physics and Astronomy | University of Waterloo
See his Github page: Roger G. Melko | rgmelko.github.io
See his page at the Perimeter Institute: Roger Melko | Perimeter Institute
Links:
What is quantum computing? Quantum computing - Wikipedia
Read about Generative Language Models in this article from the Center for Security and Emerging Technology (CSET): "What Are Generative AI, Large Language Models, and Foundation Models?" What Are Generative AI, Large Language Models, and Foundation Models? | Center for Security and Emerging Technology
Read this article from MIT TECH: What is a quantum computer? Explainer: What is a quantum computer? | MIT Technology Review
Event Location:
HENN 201
Event Time:
Thursday, November 28, 2024 | 10:00 am - 11:00 am
Event Location:
BRIM 311
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2024-11-28T10:00:00
2024-11-28T11:00:00
Measurement induced criticality in monitored quantum systems
Event Information:
Abstract: A novel aspect of recent experiments with quantum devices is that measurements can play an active role in preparing the state of the system, not just in diagnosing it. Unlike unitary evolution, the quantum collapse induced by local measurements can have a highly non-local impact on entangled quantum states, instantaneously destroying or creating new long distance correlations. I will review the surprising collective effects that can arise, such as measurement induced phase transitions and new entanglement structures. There is, however, a fundamental challenge to observing post-measurement correlations, conditioned on the outcome of many-measurements with exponentially small Born probability of recurring. I will discuss how to resolve this post-selection problem by cross-correlating experimental data with results of an approximate classical model. This allows us to reframe the measurement induced transition as a transition in the ability of a classical intelligent agent to learn the quantum state.
Event Location:
BRIM 311
Event Time:
Thursday, November 28, 2024 | 9:00 am - 12:00 pm
Event Location:
HENN 318
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2024-11-28T09:00:00
2024-11-28T12:00:00
Exotic Decay Measurements at the Experimental Storage Ring for Neutron Capture Processes
Event Information:
Abstract:
The slow (s) and rapid (r) neutron capture processes are responsible for producing almost all elements heavier than iron. Both processes require a lot of nuclear data to make more reliable predictions, and heavy-ion storage rings provide unique methods for measuring nuclear masses and exotic decay modes that can play an important role in these processes. A prime example is bound-state β− decay, where the β-electron is produced in a bound state of the decaying nuclei. This decay mode for highly-charged ions can currently only be measured at the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre in Darmstadt, Germany.
This thesis describes the analysis of the bound-state β− decay of 205Tl81+ at the ESR. 205Tl is a particularly interesting isotope due to its applications in solar neutrino spectrometry and for dating the early Solar System. A bound β-decay half-life of 291(+33,−27) days was measured, which is much longer than previously predicted. The experimental half-life determines the nuclear matrix element of this transition, which allows for the calculation of accurate astrophysical decay rates of 205Tl and 205Pb in the stellar plasma. This enables models of the s process in asymptotic giant branch (AGB) stars to provide accurate 205Pb yields, which are essential for using 205Pb as a cosmochronometer to date processes in the early Solar System, like the time required for the solar material to isolate from its parent molecular cloud. This thesis presents a preliminary determination of the isolation time of the Solar System using 205Pb.
In complement, a heavy-ion detector called PLEIADES was constructed and commissioned at the ESR, which will be used to detect decay products leaving the storage ring acceptance. PLEIADES is a δE–E telescope that uses silicon pads to measure energy loss and a scintillator stopper to measure the total ion energy. It was commissioned with a 208Pb beam at the ESR, and achieved a FWHM resolution of δZ = 0.66 and δA = 1.14.
PLEIADES and its predecessor CsISiPHOS will be used as multi-purpose detectors for future measurements in the ESR.
Event Location:
HENN 318