Events List for the Academic Year
Event Time:
Thursday, October 3, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2024-10-03T16:00:00
2024-10-03T17:00:00
New twists on topology in moiré quantum matter
Event Information:
Abstract:
Over the past two decades, condensed matter physicists have steadily mastered the isolation and control of two-dimensional van der Waals materials. These systems host a broad range of intriguing new quantum phases, enabling studies of unconventional superconductivity and strongly correlated states. Much of this progress has been driven by moiré superlattices, formed by stacking and twisting atomically thin crystalline sheets. These materials can feature flat electronic bands with strong Coulomb interactions, often giving rise to emergent collective states with exotic topological properties. I will first discuss scanning tunneling microscopy experiments that probe the microscopic origins of topological states in twisted 2D semiconductors. Then, I will present electrical transport measurements in various graphene-based moiré systems revealing topological crystals of electrons and their interplay with competing states featuring fractionally charged quasiparticles. These systems are poised to become a focus of intensive study in the coming years due to their wealth of correlation-driven topological physics and their potential applications in future quantum devices.
Bio:
Matthew Yankowitz is an Associate Professor of Physics and Materials Science & Engineering at the University of Washington. His research in experimental condensed matter physics focuses on the investigation and control of strong correlations, magnetism, superconductivity, and topology in two-dimensional van der Waals heterostructures, probed using a combination of electrical transport and scanning tunneling microscopy. Prior to joining the University of Washington, he was a postdoctoral researcher at Columbia University and received his Ph.D. in Physics from the University of Arizona. He is the recipient of an ARO Young Investigator Award (2020), an NSF CAREER Award (2021), the Lee Osheroff Richardson Science Prize from Oxford Instruments (2021), and the IUPAP Young Scientist Prize in Low Temperature Physics (2022).
Learn More:
See Matthew's lab here
View his University of Washington faculty page: Matthew Yankowitz | Department of Physics | University of Washington
Event Location:
HENN 201
Event Time:
Thursday, October 3, 2024 | 10:00 am - 11:00 am
Event Location:
AMPEL 311
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2024-10-03T10:00:00
2024-10-03T11:00:00
Introducing the Ramaniton: The quasiparticle for Raman scattering
Event Information:
In Raman scatering, pump photons that are incident on a material are able to emit or absorb materials' excitations such as phonons and orbital transitions. This process generates red-shifted (Stokes) and blue-shifted (antiStokes) photons that are usually uncorrelated with each other. When real or virtual excitations emitted by a Stokes photon are coherently absorbed by another pump photon, an entangled Stokes-antiStokes photon pair is created, in a process analogous to the formation of Cooper pairs in superconductors [1].In this talk we will show that this mechanism provides the microscopic underpinning for the phenomena of four-wave mixing in quantum optics, one of the main methods to generate squeezed states of light that are key to proposals of quantum computing, sensing, and communication with photons. We will argue that it's fruitful to take a "condensed matter physics approach" and treat Raman-interacting photons and phonons as a hybrid excitation, the Ramaniton quasiparticle [2]. The Ramaniton enables nonperturbative theories for the evolution of photons in waveguides formed by group IV semiconductors such as silicon and diamond, enabling the design of photonic devices that exploit optical phonons for optimal generation of two-mode squeezed states of light. [1] A. Saraiva, F.S.D.A. Júnior, R. De Melo E Souza, A.P. Pena, C.H. Monken, M.F. Santos, B. Koiller, and A. Jorio, Photonic Counterparts of Cooper Pairs, Phys. Rev. Lett. 119, 193603 (2017).[2] S. Timsina, T. Hammadia, S.G. Milani, F.S.D.A. Júnior, A. Brolo, and R. de Sousa, Resonant squeezed light from photonic Cooper pairs, Phys. Rev. Res. 6, 033067 (2024).
Event Location:
AMPEL 311
Event Time:
Thursday, September 26, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2024-09-26T16:00:00
2024-09-26T17:00:00
Queering Physics: A History of the Queer Rights in the USA and LGBT+ Advocacy in Physics
Event Information:
Abstract:
Queer civil rights in the USA have been hard won from direct activism and organization of a diverse coalition of people, including trans women and men, People of Color, and members of the LGBT+ community more broadly. This talk will explore this history and take an in-depth look at how principles from this history were applied to physics to make significant policy changes. The data presented will uncover a concerning climate for LGBT+ physicists, which can be even more challenging for trans persons and People of Color. The talk will conclude with concrete actions that everyone can take to become more informed about Queer Studies and implement impactful best practices in their own lives.
Bio:
Ramón Barthelemy is an associate professor of physics and astronomy at the University of Utah and a fellow of the American Physical Society. Previous to his faculty position Ramón was a Fulbright Scholar in Finland, a Science Policy Fellow in the U.S. Department of Education and a private sector consultant. His work focuses on the lives, educational experiences, and career paths of marginalized students in physics and STEM. This has included work on LGBT+ people, graduate Students of Color, and women in physics. Through this work he has become a global leader on LGBT+ inclusion in STEM with dozens of publications and over $5M in National Science Foundation funding. Ramón was the 2020 recipient of the Fulbright Finland Alumni Award, the 2021 recipient of the AAPT Doc Brown Futures award, the 2022 WEPAN Research award recipient, the 2023 Out to Innovate LGBTQ+ Educator of the Year, and a 2023 awardee for the APS 5 Sigma award for science advocacy.
Learn More:
View Ramón Barthelemy's faculty page: RAMON BARTHELEMY - Home - Faculty Profile - The University of Utah
Read University of Utah Department of Physics & Astronomy article on Ramón here: Ramón Barthelemy – Department of Physics & Astronomy (utah.edu)
Read University of Utah College of Science article on Ramón here: Humans of the U: Ramón Barthelemy | College of Science (utah.edu) and article "Ramón Barthelemy wins 2023 LGBTQ+ Educator of the Year" here: Ramón Barthelemy Out to Innovate | College of Science (utah.edu)
Event Location:
HENN 201
Event Time:
Thursday, September 26, 2024 | 10:00 am - 11:00 am
Event Location:
AMPEL Rm 311
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2024-09-26T10:00:00
2024-09-26T11:00:00
Impact of Josephson junction materials on the performance of superconducting qubits
Event Information:
Superconducting qubits are a leading modality for quantum computing, offering a favorable balance between coherence, gate times, scalability, and fidelity. I will explore the interplay between materials science and qubit performance, with a particular focus on how the materials used in Josephson junctions (JJs) affect qubit behavior. The frequency of a qubit is largely determined by the properties of JJs, which typically consist of amorphous oxide tunnel barriers. These barriers are also the likely location of most two-level systems (TLS) defects. Recently, we discovered an Alternating-Bias Assisted Annealing (ABAA) process that enables us to fine-tune JJs to achieve the desired frequency. Characterizing these ABAA post-processed JJs provides insight into the structural and chemical bonding uniformity of the amorphous oxides after ABAA processing, as well as the impact on qubit performance and TLS density.
Event Location:
AMPEL Rm 311
Event Time:
Wednesday, September 25, 2024 | 12:00 pm - 2:00 pm
Event Location:
Zoom https://ubc.zoom.us/j/69727529419?pwd=8tzHM4QhGjNpV26SgpqRhuEfAqLfyb.1
Meeting ID: 697 2752 9419
Passcode: 501860
Meeting ID: 697 2752 9419
Passcode: 501860
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2024-09-25T12:00:00
2024-09-25T14:00:00
Predictive Metrics for Moist Desquamation in Treatment Planning for Breast Radiotherapy
Event Information:
Abstract: The objective of this thesis was to establish techniques for predicting and modelling moist desquamation (MD). The work in this thesis is based on the clinical studies of the novel Carbon Fibre Adjustable Reusable Accessory (CARA) breast support device. The epidermal dose measurements, treatment plans, and skin assessments from clinical studies of the CARA device were used to develop models to be applied during treatment planning to reduce the occurrence of MD in breast radiotherapy.
In the first study of this thesis, in vivo film dosimetry was used to establish a relationship between the epidermal surface area receiving various levels of radiation dose and the corresponding skin reactions.
The results of this study indicated potential dose-area based constraints on the skin for use during treatment planning.
For the second study, the in vivo film dosimetry was compared against the Eclipse(Varian Medical Systems) treatment planning system’s Analytical Anisotropic Algorithm (AAA) and AcurosXB (AXB) dose calculation algorithms. This study produced recommendations for skin rind definitions for the two dose calculation algorithms to improve consistency in epidermal dose reporting.
In the final study, a metric was developed to predict MD based on the spatial distribution of dose across the skin. This metric maps the risk of MD across the skin’s surface based on the treatment planning system’s skin dose calculations. The predictive model was validated against a second dataset, and showed promise in its performance.
Event Location:
Zoom https://ubc.zoom.us/j/69727529419?pwd=8tzHM4QhGjNpV26SgpqRhuEfAqLfyb.1
Meeting ID: 697 2752 9419
Passcode: 501860
Event Time:
Tuesday, September 24, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-09-24T16:00:00
2024-09-24T17:00:00
Constraints on Quantum Gravity
Event Information:
We welcome you to our new Pioneers in Theoretical Physics Colloqium Series, starting this Fall, 2024.
On September 24th, we present Hirosi Ooguri, Fred Kavli Professor of Theoretical Physics & Mathematics, founding Director of the Walter Burke Institute for Theoretical Physics at the California Institute of Technology, and University Professor at the University of Tokyo.
Abstract:
Superstring theory is the best candidate for the ultimate unification of general relativity and quantum mechanics. Although predictions of the theory are typically made at extremely high energies and beyond the reach of current experiments and observations, several non-trivial constraints have been found on its low-energy effective theory. Because of the unusual ultraviolet behavior of gravitational theory, the standard argument for the separation of scales does not work for gravity, leading to robust low-energy predictions of consistency requirements at high energy. For gravitational theories in asymptotically anti-de Sitter spacetimes, we can formulate such constraints and aim to prove or falsify them using the AdS/CFT correspondence. I will review recent progress in this approach. In particular, I will prove the absence of global symmetry in quantum gravity (based on my work with Daniel Harlow) and a part of the distance conjecture in three dimensions (based on my work with Yifan Wang) and discuss the consequences of these constraints.
Bio:
Ooguri studies quantum field theory, quantum gravity, and string theory. He explores mathematical structures in these theories and uses them to develop new theoretical tools for solving fundamental questions in physics. His work in physics has also inspired progress in mathematics.
Links:
Ooguri's Caltech faculty page
Youtube playlist for Hirosi Ooguri's lectures on Topological String Theory (3 lectures)
Youtube playlist for Hirosi Ooguri science lectures
Event Location:
HENN 318
Event Time:
Monday, September 23, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-09-23T16:00:00
2024-09-23T17:00:00
Probing the Limits of Black Hole Feedback in the Most Massive Galaxies
Event Information:
Abstract:
In the past several decades it has become clear that mechanical (radio-mode) feedback from supermassive blackholes is necessary to moderate the growth of the most massive galaxies in which they reside. In particular, in the cores of galaxy clusters, the evolution of giant elliptical galaxies appear to be primarily governed by black hole feedback. Despite its apparent importance, our understanding of how feedback works is woefully incomplete, particularly when it comes to mechanical or radio-mode feedback. In this talk I will discuss two directions that we are pursuing to understand the balance between cooling and feedback in galaxy cluster cores: (i) identifying systems for which feedback appears to not work, in an effort to understand the limitations and failure modes of the feedback/cooling cycle, and (ii) searching for evidence of AGN feedback in the cores of the most distant galaxy clusters. All of these efforts require the use of data from a variety of X-ray, optical, mm-wave, and radio telescopes, including Chandra, Hubble, James Webb, and the South Pole Telescope.
Bio:
Michael McDonald is an Associate Professor of Physics at the Massachusetts Institute for Technology's Kavli Institute for Astrophysics and Space Research. He obtained his BScH and MSc degrees in Physics at Queen's University in Canada, and his PhD in Astronomy at the University of Maryland in College Park, MD. Michael spent three years as a Hubble Fellow at MIT, before being hired as an Assistant Professor in July 2015.
His research focuses on the co-evolution of massive galaxies and their super-massive black holes in the rich cluster environment. This research involves the discovery and study of the most distant assemblies of galaxies alongside detailed analyses of the complex interplay between gas, galaxies, and blackholes in the closest, most massive systems. He uses of a wide variety of ground- and space-based observatories, including (but not limited to) the Hubble and Chandra space telescopes, and the Magellan and ALMA telescopes located in Chile.
Learn More:
View Michael's MIT faculty webpage here: Michael A. McDonald » MIT Physics and personal website here: Michael McDonald - Associate Professor - MIT Kavli Institute for Astrophysics and Space Research
See Michael's Kavli Institute faculty page here: Michael McDonald - MIT Kavli Institute
MIT News: Research pulled Michael McDonald in and it won’t let go | MIT News | Massachusetts Institute of Technology
What is a supermassive black hole? Supermassive black holes: Characteristics and formation | Space
NASA animation on black holes: NASA Animation Sizes Up the Universe’s Biggest Black Holes - NASA
Event Location:
HENN 318
Event Time:
Monday, September 23, 2024 | 2:30 pm - 3:30 pm
Event Location:
HENN318
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2024-09-23T14:30:00
2024-09-23T15:30:00
PHAS Monday Tea
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:
HENN318
Event Time:
Thursday, September 19, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2024-09-19T16:00:00
2024-09-19T17:00:00
Polarized Radiation from X-Ray Pulsars
Event Information:
Abstract:
With the launch of the Imaging X-ray Polarimetry Explorer (IXPE) at the end of 2021, we have entered the era of X-ray polarization. IXPE is more than one thousand times more sensitive that previous observatories giving us "first (polarized) light" images of hundreds of X-ray sources. Looking as these objects in an essentially new way for the very first time has been exhilarating. After highlighting many of the key observations of IXPE, I will focus in particular on the observations of accreting X-ray pulsars which despite complicated magnetic field and emission geometries exhibit very simple changes in the polarization direction as the stars rotate. This straightforward evolution with spin results from the first (yet still unverified) prediction of QED that a magnetic field even in vacuum induces an index of refraction: vacuum birefringence.
Bio:
I am currently acting PHAS Department Head, professor at the University of British Columbia and a Canada Research Chair in Neutron Stars and Black Holes. My recent research has focused on compact objects: white dwarfs, neutron stars and black holes. These are the most extreme objects in the universe since the Big Bang. Astrophysicists think that they provide the power behind quasars and gamma-ray bursts, the brightest objects in the recent universe.
To put it concisely I study stars, white dwarfs neutron stars and black holes from an astrophysical perspective. Because I am a theorist I focus what these objects can tell us about fundamental physics and how our current knowledge or speculation about fundamental physics can help us understand these phenomena.
The areas of physics that my research sometimes covers include:
* High-energy astrophysics* Nuclear physics* High-energy physics (particle physics)* General relativity* Cosmology* Condensed matter physics* Atomic physics* Classical dynamics
Education
Doctoral Degree University of California at Santa Cruz, 1998Employment HistoryHead, Department of Physics and Astronomy, University of British Columbia, January 2024-Professor, Department of Physics and Astronomy, University of British Columbia, July 2013-Associate Professor, Department of Physics and Astronomy, University of British Columbia, July 2008-June 2013Assistant Professor, Department of Physics and Astronomy, University of British Columbia, July 2003-June 2008Chandra Fellow, Theoretical Astrophysics Division, Harvard-Smithsonian Center for Astrophysics, September 2000-July 2003Lee A. DuBridge Postdoctoral Fellow in Theoretical Astrophysics, California Institute of Technology, January 1998-August 2000Visiting Researcher, The Central Astronomical Observatory at Pulkovo, Saint Petersburg, Russia, June 1992-September 1992Research Assistant, National Astronomical and Ionospheric Center, Arecibo, Puerto Rico, June 1991-August 1991Research Assistant, Princeton University Observatory, Princeton, New Jersey, June 1989-September 1989
Learn More:
See Jeremy's homepage on the Stellar and High-Energy Astrophysics at UBC website: Jeremy Heyl (coolpulsars.org)
See Jeremy's faculty homepage: heyl | UBC Physics & Astronomy
UBC News: Dr. Jeremy Heyl appointed head, Physics and Astronomy | UBC Science
UBC Expert profiles: Jeremy Heyl, AB (Princeton), MSc (Cambridge), PhD (UCSC) (ubc.ca)
See NASA's webpage on the Imagining X-ray Polarimetry Explorer (IXPE): Imaging X-ray Polarimetry Explorer (IXPE) - NASA
Find NASA articles on pulsars here: 428 Search Results for "pulsar" (nasa.gov)
Event Location:
HENN 201
Event Time:
Thursday, September 19, 2024 | 10:00 am - 11:00 am
Event Location:
AMPEL 311
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2024-09-19T10:00:00
2024-09-19T11:00:00
Quantum Anomalous Hall Effects in Rhombohedral Graphene Moiré Structures
Event Information:
Abstract:
A recent series of experiments in two-dimensional moiré materials have discovered the physics of quantum Hall effect in the absence of an external magnetic field. These so-called “(Integer/Fractional) Quantum Anomalous Hall” phases have been observed in twisted transition metal dichalcogenide MoTe2 moiré heterostructure, as well as more recently in pentalayer rhombohedral graphene aligned with a hexagonal Boron-Nitride (hBN) substrate. Unlike the standard theoretical framework of the quantum Hall effect, where one has a flat band at the single-particle level, these discoveries provide a fertile ground for exploring the minimal conditions that are required to realize and stabilize such exotic phases of matter. In this talk, I will examine the microscopic origin of both the integer and fractional QAH phases in N-layer graphene aligned with hBN through a combination of Hartree-Fock methods and Exact Diagonalization. I will also discuss the delicate role of the moiré superlattice potential in determining the ultimate ground state in strongly-correlated two-dimensional moiré materials. Time-permitting, I will also briefly touch on the phenomenology of the recently observed extended quantum anomalous Hall effect in pentalayer graphene aligned with hBN.
Bio:
Adarsh completed his undergraduate degree at the University of Waterloo, and his PhD at the University of Toronto under the supervision of Yong-Baek Kim in 2021. He was a postdoctoral research associate from 2021—2024 at the Massachusetts Institute of Technology working with Senthil Todadri.
Event Location:
AMPEL 311
Event Time:
Wednesday, September 18, 2024 | 1:30 pm - 3:30 pm
Event Location:
Henn 318
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2024-09-18T13:30:00
2024-09-18T15:30:00
Electrodynamics of Non-topological Solitons
Event Information:
In this thesis, we study a class of non-topological solitons known as "Q-balls" which arise in complex scalar field theories with U(1) symmetry. We focus on the case where the U(1) symmetry is gauged and the theory admits a coupling to electromagnetism; the corresponding solitons are known as "gauged Q-balls". Using numerical simulations, we examine the dynamical behaviour of these objects in various scenarios. First, we investigate the classical stability of gauged Q-balls under assumptions of axial symmetry. Considering two different forms for the scalar field potential, we find evidence for gauged Q-ball configurations which remain stable with respect to axisymmetric perturbations of the fields. We also find evidence for unstable configurations which are quickly destroyed in response to the perturbations (for example, through dispersal of the fields or via fragmentation into smaller structures). Next, we investigate head-on collisions of gauged Q-balls at relativistic velocities. We test the effects of the electromagnetic coupling strength, initial velocity, relative phase, and relative charge of the colliding binary on the outcome of the collision. Depending on the values of these parameters, we observe a variety of distinct phenomena such as gauged Q-ball mergers, fragmentation, charge transfer, charge annihilation, Q-ring formation, and electromagnetic radiation production. Finally, we investigate the dynamics of gauged Q-balls using fully three-dimensional numerical simulations. Extending the previous analyses, we find evidence for configurations which remain classically stable against generic perturbations in three spatial dimensions. We also consider off-axis collisions of gauged Q-balls and find that the impact parameter can play a significant role in determining the outcome of the collision. Together, these results address several key questions about the dynamics of non-topological solitons in general and the stability of gauged Q-balls in particular.
Event Location:
Henn 318
Event Time:
Wednesday, September 18, 2024 | 10:00 am - 12:00 pm
Event Location:
Henn 309
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2024-09-18T10:00:00
2024-09-18T12:00:00
New Tricks for Old Stars: Studying Compact Objects Through Novel Methodologies in Timing, Energy and Imaging
Event Information:
To understand astronomical objects and their environments, it is essential to study their behavior across time, energy and space. For compact objects, these analyses provide a unique window into physics in extreme environments, probing transient behavior, accretion processes, and tests of spacetime and gravity in the high field regime. In this thesis, I present novel approaches to revolutionize timing and spectral analysis and imaging with polarimetry in astronomy. I first present two novel methodologies for astronomical timing analysis: 1) Wiener Deconvolution to resolve the response function generating time lags across different energy bands and 2) Mutual Information as a powerful tool to identify time lags without assuming underlying linearity. I establish methodological framework and demonstrate efficacy of methodologies through toy models for generalized utilization of astronomical timing and lag analysis. I then present the results of novel methodologies applied to radio data from the black hole binary MAXI J1820+070. These approaches not only help in identifying time lags with much higher accuracy and precision, but also reveal numerous previously undetected lags, offering new insights into how the compact jet in MAXI J1820+070 behaves across different energies. I then extend the astronomical application of Wiener Deconvolution to 2D, enabling estimates of the first ever high resolution X-ray polarimetry images, and present preliminary results for the Supernova Remnant Cas A. Finally, I explore magnetar spectral line analysis and modeling, and show how we can learn about the behaviour of magnetic fields at their most intense through spectral lines detected from magnetars with current and future detectors.
Event Location:
Henn 309
Event Time:
Monday, September 16, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-09-16T16:00:00
2024-09-16T17:00:00
Roadmap to a compendium of supermassive black hole images
Event Information:
Abstract:
Following the transformational science enabled by the Event Horizon Telescope, we now focus on expanding the parameter space in terms of mass, spin and the role of magnetic field in extreme gravitational environment. It is thus imperative that imaging the silhouette of several black holes, beyond SgrA* and M87*, will provide vital constraints that will also probe the nature of (non-) General Relativity on a cosmological scale. I will present an overview of the fundamental physics that goes into this study from a multiwavelength perspective while also referring to an ongoing study with the EHT to image the photon rings and accretion flows of more AGNs in the nearby Universe. I will also show how the next generation EHT observations both from ground and space can be fundamental in this endeavour.
Bio:
Postdoctoral Researcher Venkatessh Ramakrishnan works at both the Finnish Centre for Astronomy with ESO and Aalto University’s Metsähovi Radio Observatory.
Links:
View his LinkedIn profile page
Aalto University Researchers' bio: Researchers from Aalto University, University of Turku, and Finnish Centre for Astronomy with ESO participated in the project taking a photo of the black hole at the centre of our galaxy
University of Turku (Finland) publications page for Venkatessh Ramakrishnan
Article: University of Turku (Finland): Scientists reveal new images of a black hole - Proof of a persistent black hole shadow
Article: Recognition from the Senate of Chile and the University of Concepción for Dr. Ramakrishnan's work on black holes
Event Location:
HENN 318
Event Time:
Monday, September 16, 2024 | 2:30 pm - 3:30 pm
Event Location:
HENN 318
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2024-09-16T14:30:00
2024-09-16T15:30:00
PHAS EDI Committee Monday Tea
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
Pedro Villalba Gonzalez
See you there!
Event Location:
HENN 318
Event Time:
Monday, September 16, 2024 | 12:30 pm - 2:30 pm
Event Location:
Hybrid: in-person at TRIUMF ISAC-II Conference Room (4004 Wesbrook Mall) and Zoom: https://ubc.zoom.us/j/62516482273?pwd=5UBub9EbYj9lLJZevXYfa31Heo76OP.1
Meeting ID: 625 1648 2273 Password: 129025
Meeting ID: 625 1648 2273 Password: 129025
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2024-09-16T12:30:00
2024-09-16T14:30:00
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 was 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 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 isolation time of solar material 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:
Hybrid: in-person at TRIUMF ISAC-II Conference Room (4004 Wesbrook Mall) and Zoom: https://ubc.zoom.us/j/62516482273?pwd=5UBub9EbYj9lLJZevXYfa31Heo76OP.1
Meeting ID: 625 1648 2273 Password: 129025
Event Time:
Thursday, September 12, 2024 | 4:00 pm - 5:00 pm
Event Location:
Mathematics Annex (MATX) 1100, 1986 Mathematics Road, UBC-V campus
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2024-09-12T16:00:00
2024-09-12T17:00:00
Exploring Exoplanet Demographics with Kepler, TESS, and Beyond
Event Information:
Abstract:
Searches for planets beyond the Solar System ("exoplanets") have been spectacularly successful in identifying thousands of diverse new worlds, placing the Solar System in context and informing our understanding of how planets form and evolve. Finding large numbers of planets also enables demographic studies, through which we can uncover which types of planets are more common than others and why. I will highlight contributions to exoplanet discovery and demographics, from planets of all sizes and implications for the existence of other Earths from Kepler, to the exciting potential of TESS to significantly expand our understanding of planets around nearby, bright stars amenable to follow-up and further characterization. Finally, I will identify a set of important open questions that remain to be answered and outline future goals to push exoplanet science to new frontiers, especially in the context of the search for habitable worlds.
Bio:
I am an Assistant Professor in the Department of Physics and Astronomy at the University of British Columbia.My research is primarily focused on exoplanet detection, characterization, and demographics. I approach these fields in data-driven ways, developing and improving techniques to extract as much as we can from exoplanet surveys while answering key science questions along the way.
I was previously a Torres postdoctoral fellow and TESS postdoctoral associate at MIT. I obtained my PhD in Astronomy from UBC in 2020.
Learn More:
See Michelle's website here: About | Michelle Kunimoto (mkunimoto.github.io)
See Michelle's PHAS faculty page here: mkuni | UBC Physics & Astronomy
Find out more about exoplanets: The exoplanet zoo | Canadian Space Agency (asc-csa.gc.ca)
Event Location:
Mathematics Annex (MATX) 1100, 1986 Mathematics Road, UBC-V campus
Event Time:
Thursday, September 12, 2024 | 10:00 am - 11:00 am
Event Location:
AMPEL 311
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2024-09-12T10:00:00
2024-09-12T11:00:00
Sliding Ferroelectricity in Rhombohedral MoS2: A New Approach to Nonvolatilely Switch the Interaction between Light and Matter
Event Information:
Abstract:
The tunability in the stacking of layered materials with van der Waals bonding provides a new and powerful approach to engineer their physical properties. Sliding ferroelectricity is one such example where an electric field drives one layer of materials to move relative to its neighbours due to an out-of-plane electric polarization arising from interlayer coupling. Sliding ferroelectricity can therefore occur in traditionally non-ferroelectric materials and has been observed in artificially stacked boron nitrides and transition metal dichalcogenides (TMDs). In this talk, I will show that such a hysteric phenomenon can occur in chemically synthesized rhombohedral molybdenum disulfide (3R-MoS2) crystals with pre-existing domain walls. I will first discuss our studies on domain characterization using photocurrent and scanning probe microscopy. I will then show that these polarization domains and their switching behavior can be probed by optical spectroscopy, revealing the existence of a variety of switching pathways. Due to their strong excitonic effects and sliding ferroelectricity, rhombohedral TMDs can be built into nonvolatile optical memories with high performances.
Bio:
We are an optical spectroscopy group studying light matter interaction in low-dimensional materials. We are currently focused on exploring how topology, correlation effects, and other emergent degrees of freedom interact with each other in two-dimensional van der Waals materials such as graphene, phosphorene, transition metal dichalcogenide, hexagonal boron nitride, high-Tc cuprates and their heterostructures. Our expertise includes ultrafast optical spectroscopy with diffraction-limited resolution at low temperatures and strong magnetic fields as well as nearfield optical microscopy. In the past, we have utilized ultrafast nonlinear optical spectroscopies to reveal the crystal and electronic structure of TMDCs. We are currently interested in developing novel optical microscopy techniques to interrogate the 2D material’s intrinsic response and to control them with the strong optical field provided by coherent laser light. In the meantime, novel devices based on bulk photovoltaic effect and topological superconductivity are being actively explored in the group for classical and quantum applications.
Learn More:
Ziliang's Investigator biography page at the Stewart Blusson Quantum Matter Institute: Ziliang Ye - Stewart Blusson Quantum Matter Institute (ubc.ca)
Ziliang's faculty page for the Department of Physics & Astronomy: zlye | UBC Physics & Astronomy
Event Location:
AMPEL 311
Event Time:
Thursday, September 12, 2024 | 9:00 am - 11:00 am
Event Location:
Room 200, Graduate Student Centre (6371 Crescent Road)
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2024-09-12T09:00:00
2024-09-12T11:00:00
Scaling theories and simulation of ductile yielding in amorphous solids
Event Information:
Amorphous solids are a diverse class of materials that have significant interest owing to their ubiquity in industry, yet a unifying theory to describe their mechanical response to load under temperature is lacking. Using a combination of highly parallelized numerical routines to simulate an elastoplastic model (EPM) of amorphous solids, as well the corresponding mean-field theory, I develop a scaling theory for the yielding of amorphous solids for non-zero temperature and driving rates.
First, I simulate very large systems at zero temperature. Here, ductile yielding proceeds through localized rearrangements that, under sufficient load, self-organize into extended avalanches. I study the appearance of the recently described stability plateau, which violates the existing athermal scaling theories for amorphous yielding. Using finite-size scaling, I show that this deviation originates in the spatial extent of the largest avalanches, and that this plateau in turn affects the energy available to avalanches. Consequently, this changes the scaling description for amorphous yielding at zero temperature.
Second, I introduce a temperature-dependent failure to the EPM. With extensive numerical simulations, as well as scaling arguments from mean-field theory, I map out a phase-diagram for different regimes of behaviour, depending on both temperature and the rate at which energy is loaded into the system. I verify the boundaries of the phase-diagram by showing changes in behaviour across each of the phase lines, test predictions for avalanche size and flow stress in each flow regime. Contrary to recently proposed theories based on mean-field modelling alone, I show that the competition between driving rate and temperature differs between the continuously flow regime (in which avalanches merge) and the intermittent flow regime.
Finally, motivated by experimental data on the creep of disordered mylar sheets, I study creep-flow in amorphous solids by considering an EPM at fixed stress and non-zero temperature. Here, we show that creep proceeds through cascades of correlated activity that occur over extremely long timescales. These ``thermal avalanches'' have long periods of quiescence, yet I argue they obey the same scaling laws and underlying physics as the mechanical avalanches of the ductile yielding transition.
Event Location:
Room 200, Graduate Student Centre (6371 Crescent Road)
Event Time:
Monday, September 9, 2024 | 4:00 pm - 5:00 pm
Event Location:
HENN 318
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2024-09-09T16:00:00
2024-09-09T17:00:00
Probing Quasar Outflows Through Absorption Line Spectroscopy
Event Information:
Abstract:
Quasars, among the most luminous astrophysical systems, are powered by supermassive black holes (SMBHs) accreting gas at the centers of their host galaxies. A critical aspect of quasar physics is the presence of powerful outflows, often identified through broad absorption lines (BALs) in quasar spectra. These outflows are key to understanding the interaction between SMBHs and their host galaxies, which is crucial for unraveling the processes that drive their co-evolution. In this talk, I will focus on the time variability of these outflows through long-term spectral monitoring of BAL quasars, a powerful tool for studying their origins and evolution. I will present a comprehensive analysis of time variability in C IV BALs over a span of seven years, based on a sample of 64 BAL quasars observed with the Southern African Large Telescope. The discussion will highlight both short- and long-term variations in absorption strength and examine how various quasar and BAL properties influence these changes. Additionally, I will talk about two unusual sources from our sample in detail, presenting insights from their extreme variability events and what they reveal about the nature of quasar outflows.
Bio:
I am an observational astrophysicist with a PhD from the Inter University Centre for Astronomy and Astrophysics (IUCAA), India, now pursuing a postdoctoral fellowship at Western University, Canada. My research focuses on extragalactic astronomy, specializing in quasar formation and evolution. I have extensive experience in data analysis techniques, programming and scientific writing.
Learn More:
See Amoral's LinkedIn profile here: (39) Aromal Pathayappura | LinkedIn
NASA information about Quasars :NASA’s Webb Will Use Quasars to Unlock the Secrets of the Early Universe - NASA
Event Location:
HENN 318
Event Time:
Monday, September 9, 2024 | 2:30 pm - 3:30 pm
Event Location:
HENN 318
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2024-09-09T14:30:00
2024-09-09T15:30:00
PHAS EDI Committee Monday Tea Event Launch
Event Information:
Welcome everyone to the launch of the PHAS EDI 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
Pedro Villalba Gonzalez
See you there!
Event Location:
HENN 318