Events List for the Academic Year
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Thursday, April 8, 2021 | 2:00 pm - 4:00 pm
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2021-04-08T14:00:00
2021-04-08T16:00:00
Departmental Doctoral Oral Examination (Thesis Title: “Holographic quantum matter: toy models and physical platformsr”)
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Abstract:
In recent years a new paradigm has emerged to investigate non-Fermi liquids without quasiparticles, based on the exactly-solvable Sachdev-Ye-Kitaev model which consists of a large number of fermions with all-to-all, random Gaussian interactions. This model exhibits a rich phenomenology at low energy, including power-law decaying spectral functions, maximal chaos and connections to black hole horizons in anti-de Sitter spacetime. These intriguing properties have inspired a broad research program at the intersection of condensed matter physics, quantum information and quantum gravity.
In this thesis we explore the phases and phase transitions occurring in Sachdev-Ye-Kitaev models that are coupled in various ways, with an eye on physical platforms that could enable their realization in condensed matter systems. This journey takes us from the investigation of quantum chaos and revival dynamics in traversable wormholes, all the way to the physics of disordered graphene flakes and unconventional superconductivity.
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Event Time:
Thursday, April 8, 2021 | 10:00 am - 11:00 am
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2021-04-08T10:00:00
2021-04-08T11:00:00
CM Seminar - Recent Developments in Hybrid and Inorganic Perovskite Halides
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CM Seminar - Thu, April 8th 10am
https://ubc.zoom.us/j/64183011430?pwd=U2lFNXEwSmlBRWVBdTR5OG1ZdlVSZz09
Meeting ID: 641 8301 1430
Passcode: 113399
Talk Title: Recent Developments in Hybrid and Inorganic Perovskite Halides
Speaker: Anthony K. Cheetham - Materials Research Laboratory, UCSB
Abstract: Hybrid organic-inorganic perovskites are found in a number of important families, including the lead-based halides (e.g. CH3NH3PbI3) and the formates (e.g. [(CH3)2NH2]Zn(HCOO)3) [1], as well as systems with the ReO3 structure [2]. The lead halide perovskites have attracted a great deal of attention in the last decade on account of their excellent performance as active layers in solar cells and other optoelectronic devices. I shall discuss some of our recent work which has focused on the search for lead-free hybrid and inorganic double perovskites such as (CH3NH3)2AgBiBr6 and Cs2AgSbBr6 [3]. I shall also describe some B-site vacant perovskites based on platinum [4] and ruthenium [5], as well as recent developments in the area of hybrid layered double perovskite halides [6]. Our current work on ruthenium systems is enabling us to explore the influence of chemical bonding on spit-orbit coupling effects.
1. W. Li, Z. M. Wang, F. Deschler, S. Gao, R. H. Friend and A. K. Cheetham, Nature Rev. Mater. 2, 16099 (2017)
2. H. A. Evans, Y. Wu, R. Seshadri and A. K. Cheetham, Nature Rev. Mater. 5, 196 (2020)
3. Wei, Z. Deng, S. Sun, F. Zhang, D. M. Evans, G. Kieslich, S. Tominaka, M. A. Carpenter, P. D. Bristowe, and A. K. Cheetham, Chem. Mater. 29, 1089 (2017); Z. Deng, F. Wei, F. Brivio, Y. Wu, S. Sun, P. D. Bristowe, and A. K. Cheetham, J. Phys. Chem. Lett, 8, 5015 (2017); F. Wei, Z. Deng, S. Sun, N. T. Putri Hartono, H. L. Seng, T. Buonassisi, P. D. Bristowe, and A. K. Cheetham, Chem. Comm. 55, 3721 (2019)
4. H. A. Evans, D. H. Fabini, J. Andrews, M. Koerner, M. Preefer, G. Wu, F. Wudl, A. K. Cheetham and R. Seshadri, Inorg. Chem. 57, 10375 (2018); H. A. Evans, J. L. Andrews, D. H. Fabini, M. B. Preefer, G. Wu, A. K. Cheetham, F. Wudl, and R. Seshadri, Chem. Comm. 55, 588 (2019)
5. P. Vishnoi, J. L. Zhuo, T. A. Strom, G. Wu, S. D. Wilson, R. Seshadri, and A. K. Cheetham, Angew. Chemie Intl. Ed. Eng. 59, 8974 (2020); P. Vishnoi, J. L. Zuo, J. A. Cooley, L. Kautzsch, A. Gómez‐Torres, J. Murillo, S. Fortier, S. D. Wilson, R. Seshadri, A. K. Cheetham, Angew. Chemie Intl. Ed. Eng. 60, 5184 (2021)
6. L. L. Mao, S. Teicher, C. C. Stoumpos, R. M. Kennard, R. A. DeCrescent, G. Wu, J. A. Schuller, M. L. Chabinyc, A. K. Cheetham and R. Seshadri, J. Amer. Chem. Soc. 141, 19099 (2019); H. A. Evans, L. L. Mao, R. Seshadri and A. K. Cheetham, Ann. Rev. Mater. Sc. 51, (2021)
Bio: Tony Cheetham is a Research Professor at the University of California, Santa Barbara, and a Distinguished Visiting Professor at the National University of Singapore. He was formerly the Goldsmiths’ Professor of Materials Science at the University of Cambridge (2007-2017) and the Treasurer and Vice-President of the Royal Society (2012-2017). He obtained his D.Phil. at Oxford in 1972 and did post-doctoral work in the Materials Physics Division at Harwell. He joined the Chemistry faculty at Oxford in 1974, and then moved to UC Santa Barbara in 1991 to become Professor in the Materials Department. From 1992-2004 he was the Director of UCSB’s Materials Research Laboratory. Cheetham was knighted by the Queen for “Services to Materials Chemistry, UK Science and Global Outreach” in January 2020
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Thursday, April 1, 2021 | 4:00 pm - 5:00 pm
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2021-04-01T16:00:00
2021-04-01T17:00:00
Physics Pranks and Astronomical Antics
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1st April has traditionally been a day for japes and high jinks in many realms of life - with science not being entirely excluded! In observance of this day I will review the use of humour in physics and astronomy, focusing on some specific examples, particularly those involving April Fool's Day.
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Thursday, April 1, 2021 | 10:00 am - 11:00 am
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2021-04-01T10:00:00
2021-04-01T11:00:00
CM Seminar - Frontiers in Quantum Information Science
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https://ubc.zoom.us/j/64183011430?pwd=U2lFNXEwSmlBRWVBdTR5OG1ZdlVSZz09
Meeting ID: 641 8301 1430
Passcode: 113399
Title: Frontiers in Quantum Information Science
Speaker: Jacob Taylor – University of Maryland
Abstract: Quantum information science (QIS) promises dramatic improvements in our ability to understand the physical world and in our capabilities for measurement, communication, and computation. Over the past five years, a worldwide expansion of government-funded research and development has combined with an unprecedented investment from the private sector to dramatically accelerate progress in realizing the potential of quantum systems. In this talk I will discuss the re-envisioning of the U.S. research and development approach to QIS enacted over the past two years through the National Quantum Initiative and other efforts, and consider future opportunities and challenges for academia, industry, government, and the public. I will also touch upon several research frontiers of personal interest in the space, specifically the interplay between quantum device development and physical understanding, from probing many-body systems with qubits to searching for dark matter using advanced quantum sensors to even exploring terrestrial tests of the quantum nature of gravity.
Bio: Jake Taylor has been doing research in quantum information science and quantum computing for the past two decades, most recently at the National Institute of Standards and Technology and at the Joint Quantum Institute and the Joint Center for Quantum Information and Computer Science at the University of Maryland, College Park. In addition to his research, he spent the last three years as the first Assistant Director for Quantum Information Science at the White House Office of Science and Technology Policy, where he led the creation and implementation of the National Quantum Initiative (quantum.gov) and the COVID-19 High Performance Computing Consortium (covid19-hpc-consortium.org). Now taking a year as a TAPP Fellow at Harvard's Belfer Center for Science and International Affairs, Jake is looking at how lessons learned in implementing science and tech policy for an emerging field can enable public purpose in other areas. He is the author of more than 150 peer reviewed scientific articles, a Fellow of the American Physical Society and the Optical Society of America, and recipient of the Silver and Gold medals from the Department of Commerce. He can be found on twitter @quantum_jake and atquantumjake.org.
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Wednesday, March 31, 2021 | 11:00 am - 12:00 pm
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2021-03-31T11:00:00
2021-03-31T12:00:00
Sub-leading Soft Photons and Gravitons
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Soft factorization has been shown to hold to sub-leading order in QED and to sub-sub-leading order in perturbative quantum gravity, with various loop and non-universal corrections that can be found. In a recent paper, we show that all terms factorizing at tree level can be uniquely identified as boundary terms that exist already in the classical expressions for the electric current and stress tensor of a point particle. Further, it turns out that one cannot uniquely identify such boundary terms beyond the sub-leading or sub-sub-leading orders respectively, providing evidence that the factorizability of the tree level soft factor only holds to these orders. In this talk, I will first introduce and motivate the soft theorems, and then explain our recent results. I'll also show how our new classical intuition is reflected in the calculation of quantum scattering amplitudes.
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Monday, March 29, 2021 | 3:00 pm - 4:00 pm
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2021-03-29T15:00:00
2021-03-29T16:00:00
The Quest for High Hubble Constant Harmony
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The most precise of the direct measurements of the current rate of cosmic expansion (the Hubble constant) is inconsistent with the even more precise, but indirect, model-dependent inferences. In particular the Riess et al. (2020) measurement is more than four standard deviations higher than the inference based on the standard cosmological model, with its free parameters constrained by Planck satellite observations of the cosmic microwave background. In this talk I will explain the beautifully simple physics that allows for a prediction of the Hubble constant from observations of temperature and polarization patterns in the sky at millimeter wavelengths and I will entertain the exciting possibility that the origin of this discrepancy is a deficiency of the standard cosmological model.
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Friday, March 26, 2021 | 12:00 pm - 2:00 pm
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2021-03-26T12:00:00
2021-03-26T14:00:00
Departmental Doctoral Oral Examination (Thesis Title: “The search for jovian and saturnian irregular moons and a study of their luminosity functions”)
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Abstract: (please see this link)
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Thursday, March 25, 2021 | 4:00 pm - 5:00 pm
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2021-03-25T16:00:00
2021-03-25T17:00:00
Attosecond Science
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An electron that multiphoton ionizes is immediately subject to the light's electric field that will control its short-term future. This control enables a gas of atoms to produce intense VUV or soft X-ray beams. Since we can precisely control the infrared beam, we can synthesize attosecond soft X-ray pulses - pulses that are the shortest controlled events ever systematically produced. For a complex atom (such as xenon), the recollision electron shares its energy in any multi-electron interaction. Measuring the energy share encodes multielectron dynamics such as the Fano resonance structure in helium and the Giant Plasmon resonance in Xenon.
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Thursday, March 25, 2021 | 10:00 am - 11:00 am
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2021-03-25T10:00:00
2021-03-25T11:00:00
CM Seminar - Spin, Charge, and Phonon Coupling Effects in 2D Materials
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CM Seminar - Thu, March 25, 10am (PST)
https://ubc.zoom.us/j/64183011430?pwd=U2lFNXEwSmlBRWVBdTR5OG1ZdlVSZz09
Meeting ID: 641 8301 1430
Passcode: 113399
Abstract: The coupling between spin, charge, and lattice degrees of freedom plays an important role in a wide range of fundamental phenomena. 2D material is an emerging platform for studying these coupling effects. In this talk, I will present a couple examples along this direction. I will firstly discuss the observation of antiferromagnetic exciton and multiple exciton phonon bound states in zigzag antiferromagnet NiPS3. I will then present the observation of valley phonons, i.e. phonons with momentum vectors pointing to the corners of Brillouin zone, and their interaction with spins in a monolayer semiconductor WSe2. We identified the efficient intervalley scattering of quasi particles in both exciton formation and light emission process. These understandings enable us to unravel a series of photoluminescence peaks as valley phonon replicas of neutral and charged dark excitons.
Short Bio: Xiaodong Xu is a Boeing Distinguished Professor in the Department of Physics and the Department of Materials Science and Engineering at the University of Washington. He received his PhD (Physics, 2008) from the University of Michigan and then performed postdoctoral research (2009-2010) at the Center for Nanoscale Systems at Cornell University. His nanoscale quantum-optoelectronics group at University of Washington focuses on creation, control, and understanding of novel device physics based on low-dimensional quantum materials.
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Final PhD Oral Examination (Thesis Title: “Scanning Tunnelling Microscopy of Topological Materials”)
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2021-03-25T09:00:00
2021-03-25T11:00:00
Final PhD Oral Examination (Thesis Title: “Scanning Tunnelling Microscopy of Topological Materials”)
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Abstract:
Topological materials have been at the forefront of condensed matter physics research over the past few decades. Characterised by electronic bands with non-trivial topological invariants, topological materials exhibit a number of interesting electronic properties, such as conducting chiral boundary states and linear electronic dispersions, and have been theorised for use in a variety of applications ranging from spintronic devices to quantum computing. Recently, topological semimetals were discovered, where the bulk electronic bands are understood in the framework of the high-energy relativistic Dirac equation and its conditional variations, the Weyl and Majorana equations. Furthermore, the vast permutations of material compounds available results in a nearly infinite sandbox for researchers to study, which has resulted in topological semimetals that have no high-energy analogue. One of such material classifications is the nodal-line semimetal, characterised by linear electronic band crossings that form lines or loops in momentum space. These nodal-line semimetals also exhibit exotic surface states, named drumhead states, which are an interesting and exciting new state with promises in high-temperature superconductivity and quantum computation. A large effort is being placed to find materials that can be used to study the fundamental properties of these materials and their resultant surface states.
Scanning tunnelling microscopy (STM) provides a perfect tool to study the topological properties of materials, able to atomically resolve the surface structure and also provide insight into scattering selection rules, which are deeply dependent on the band topology. Two topological materials were studied using STM in this thesis: the topological nodal-line semimetal ZrSiTe and the topological insulator (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$. ZrSiTe was studied with an emphasis on the quasiparticle scattering characteristics, measured using Fourier-transform scanning tunnelling spectroscopy. Two main scattering features are examined, one relating to the nodal line, and the other arising from the drumhead surface state. These studies mark the first time a drumhead state has been observed using a real space measurement. (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ was studied with an emphasis on the nano-scale transport characteristics, measured using 4-probe STM and scanning tunnelling potentiometry. Effects of step edges and domain boundaries on the local resistance are studied for a fractional substitution of $x = 0.19$.
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Monday, March 22, 2021 | 3:00 pm - 4:00 pm
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2021-03-22T15:00:00
2021-03-22T16:00:00
The Magnetic Milky Way in Three Dimensions
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Magnetic fields thread our Milky Way Galaxy, influencing interstellar physics from cosmic ray propagation to star formation. The magnetic interstellar medium is also a formidable foreground for experimental cosmology, particularly for the quest to find signatures of inflation in the polarized cosmic microwave background (CMB). Despite its importance across scientific realms, the structure of the Galactic magnetic field is not well understood. Observational tracers like polarized dust emission yield only sky-projected, distance-integrated measurements of the three-dimensional magnetic structure. I will discuss new ways to probe interstellar magnetism in three dimensions, by combining high-resolution observations of Galactic neutral hydrogen with recent insights into how gas morphology encodes properties of the ambient magnetic field. These 3D maps are a new tool for understanding the magnetic interstellar medium and the polarized foreground to the CMB.
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Monday, March 22, 2021 | 9:00 am - 11:00 am
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2021-03-22T09:00:00
2021-03-22T11:00:00
Final PhD Oral Examination (Thesis Title: “Development of a Single Vacuum Ultra-Violet Photon-Sensing Solution for nEXO”)
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Thursday, March 18, 2021 | 4:00 pm - 5:00 pm
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2021-03-18T16:00:00
2021-03-18T17:00:00
The entropy of Hawking Radiation
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Black holes are interesting spacetime configurations predicted by general relativity. When quantum mechanics is taken into account, black holes are found to emit thermal radiation, called "Hawking radiation".
During the past couple of years a surprising new way to compute its entropy has emerged. This result indicates that the black hole formation and evaporation is consistent with standard quantum mechanical laws.
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Thursday, March 18, 2021 | 1:00 pm - 3:00 pm
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2021-03-18T13:00:00
2021-03-18T15:00:00
Departmental Doctoral Oral Examination (Thesis Title: “Quantum tasks in holography”)
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Abstract:
The AdS/CFT correspondence relates quantum gravity in asymptotically AdS spacetimes to conformal field theories living on the boundary of that spacetime. Here, we initiate a new perspective on the AdS/CFT correspondence. In particular we study relativistic quantum tasks, which are quantum computations with inputs and outputs occurring at specified spacetime locations. We note that the AdS/CFT correspondence implies the same tasks are possible in quantum gravity in AdS spacetimes as are possible in the dual CFT. Using this, we find a relationship between the existence of overlaps in certain light cones in the bulk spacetime and entanglement in the boundary CFT. This complements the usual perspective on geometry and entanglement in AdS/CFT, which relates minimal surfaces in AdS to entanglement in the CFT. Further, we point out various instances where this bulk/boundary tasks relationship implies novel statements about tasks.
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Wednesday, March 17, 2021 | 11:00 am - 12:00 pm
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2021-03-17T11:00:00
2021-03-17T12:00:00
Pulsar Timing Arrays CHIME in on Gravitational Waves
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The success of gravitational wave observations of stellar mass black hole mergers and neutron star mergers has proven that observational gravitational wave astronomy has an important part to play in coming years. However, ground-based laser interferometers can access only a limited portion of the gravitational wave spectrum. Low-frequency gravitational waves, such as those from supermassive black hole binaries, require different observational strategies.
One such strategy is high-precision pulsar timing arrays (PTAs). PTAs observe sets of millisecond pulsars, generating high-precision, long-term timing solutions. Gravitational wave signals from supermassive black hole binaries will appear in these timing solutions as correlated timing fluctuations with a unique angular signature. Unlike signals from stellar mass compact binary coalescences, these gravitational wave signals will be visible on approximately decade timescales; they are expected to appear gradually and grow over time.
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is one such PTA, primarily using data from the Green Bank Telescope and the Arecibo Observatory. The most recent NANOGrav results strongly suggest a stochastic common-spectrum process, which may prove to be an early indicator of a gravitational wave signal.
In this talk, I will provide an introduction to pulsar timing arrays, discuss the recent NANOGrav results, and look forward to the emerging contributions of CHIME/Pulsar in pulsar timing array science.
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Monday, March 15, 2021 | 3:00 pm - 4:00 pm
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2021-03-15T15:00:00
2021-03-15T16:00:00
Radio-based Studies of Solar Flares: Looking Ahead to the Next Solar Maximum in 2025
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Abstract: New Jersey Institute of Technology's Expanded Owens Valley Solar Array (EOVSA) has amply demonstrated the power of radio imaging spectroscopy for imaging and quantitative diagnostics of both the flaring and non-flaring Sun. The unique sensitivity of radio emission to the flaring coronal magnetic field has been dramatically shown in a series of recent papers, along with accelerated-electron diagnostics in the same volume. The coming solar maximum (cycle 25) is slated to peak in 2025-2026, which promises to bring new space- and ground-based instruments together with EOVSA to provide our best observational view of solar flares ever achieved. Here we describe the preparations underway and what we hope to learn in the coming solar cycle from radio-based studies of solar flares.
Bio: Dale Gary received his B.S. in Physics from University of Michigan in 1976, and Ph.D. in Astro-Geophysics from University of Colorado, Boulder, in 1982. He served in various research positions at Caltech from 1982-1997, attaining the position of Research Fellow in Astrophysics. He joined the faculty of NJIT in 1997, where he is now Distinguished Professor in the Department of Physics and Director of the Expanded Owens Valley Solar Array, near Big Pine, CA. He is currently serving as Chair of the Solar Physics Division of the American Astronomical Society, and is a Fellow of the American Association for the Advancement of Science.
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Friday, March 12, 2021 | 2:00 pm - 4:00 pm
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2021-03-12T14:00:00
2021-03-12T16:00:00
Final PhD Oral Examination (Thesis Title: "Adaptive Radiotherapy Treatment Corrections to Account for Patient-Specific Systematic Soft Tissue Deformations: Prostate, Lung, and Head & Neck Cancer”)
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Thursday, March 11, 2021 | 4:00 pm - 5:00 pm
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2021-03-11T16:00:00
2021-03-11T17:00:00
The Connections Between Physics and Finance
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The connection between physics and finance goes back hundreds of years, and the names of the earliest physicists who studied finance may be surprising. In the 18th century Bernoulli discovered Euler's constant e when investigating compound interest; more recently Jim Simons – of the Chern-Simons QFT fame – runs one of the most successful hedge funds of all time, and Nigel Goldenfield – who pioneered renormalization group theory in condensed matter – founded a financial-derivative software company.
Today many PhD graduates find a natural home in the financial industry. This talk will attempt to shed light as to why the fit is so natural, by exploring three facets of finance through the investment narrative: how does an investor choose their portfolio, how do they gauge the success of their investments, and finally how do they project and manage risk. I will spend the bulk of the talk on the pricing of derivative securities since this is my area of expertise, and the area that draws the most physicists.
First, I will discuss the types of problems that need to be solved, from choosing an investment, to forecasting financial risk, to hedging these risks by using derivative securities.
Second, the mathematical machinery required to solve these problems will be discussed, focusing on stochastic calculus, which has emerged as the lingua franca of financial security pricing. Stochastic calculus coupled with the concept of arbitrage freedom gives a very sound mathematical basis for the pricing of derivative securities.
Finally, I will discuss the models that are used to describe financial observables – such as prices, correlations, volatilities, and credit – and look at how the models have evolved as the important aspects of the data emerged.
When I first made the decision to move into finance, I was worried that the work would be a boring application of the mathematics I learned in my PhD. Happily, I was incorrect, as the field is deep with many interesting problems to study and novel mathematics to learn, and I hope to convey this in my talk.
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Thursday, March 11, 2021 | 10:00 am - 11:00 am
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2021-03-11T10:00:00
2021-03-11T11:00:00
CM Seminar: Microscopics of Quantum Annealing in the Disordered Dipolar Ising Ferromagnet LiHo1-xYxF4
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https://ubc.zoom.us/j/64183011430?pwd=U2lFNXEwSmlBRWVBdTR5OG1ZdlVSZz09
Meeting ID: 641 8301 1430
Passcode: 113399
Abstract: The technique of “quantum annealing” (QA) involves using quantum fluctuations to find the global minimum of a rugged energy landscape. For some problems it has been shown to produce faster optimization than thermal annealing (TA), and it has been adopted as one technique used for quantum computing (adiabatic quantum computing). Conceptually, QA is often framed in the context of the disordered transverse field Ising model, where a magnetic field applied perpendicular to the Ising axis tunes the quantum fluctuations and enables a “better” (lower energy) spin configuration to be obtained via quantum tunneling. A celebrated material example of this model, LiHo0.45Y0.55F4, was shown decades ago to exhibit faster dynamics after a QA protocol, compared to a TA protocol. However, little is known about the actual process of optimization involved and ultimately what the optimal spin configurations are like.
We have set out to understand the microscopics of QA in LiHo0.45Y0.55F4 using diffuse magnetic neutron scattering. We performed the same protocols as initially used to demonstrate QA in this material, and find faster dynamics at the end of the QA protocol compared to TA. This confirms the initial result, which was obtained from ac susceptibility. However, we also clearly observe experimental evidence that the transverse field does more than just introduce quantum fluctuations; namely, it produces random longitudinal fields, which had been previously predicted. Thus, while the material does respond to QA differently than TA, it is not a simple annealing problem; the energy landscape being optimized is changing as the optimization proceeds. Understanding this version of quantum annealing could be of interest in the context of adiabatic quantum computing, possibly for designing new algorithms, or for accounting for unwanted experimental effects.
Bio: Kate joined the faculty of the Department of Physics at Colorado State University in 2015. Her research focus is on synthesis and characterization of frustrated and quantum magnetic materials, in particular using neutron scattering. She earned her PhD from McMaster University in 2012 and was a postdoctoral fellow at NIST/Johns Hopkins University, as well as in the Chemistry Department at Colorado State University, before taking up her current position. In her spare time she loves hanging out with her 2 year old son, and is currently studying Bayesian statistics and machine learning.
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Wednesday, March 10, 2021 | 11:00 am - 12:00 pm
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2021-03-10T11:00:00
2021-03-10T12:00:00
Gravitational coupling of microscopic source masses: challenges for future quantum Cavendish experiments
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No experiment today provides evidence that gravity requires a quantum description. It has been suggested that one can at least exclude the possibility for semiclassical gravity by performing an experiment whose outcome cannot be explained by a purely classical source mass configuration. It turns out that such “quantum Cavendish” experiments are challenging, to say the least. I highlight some of the practical aspects of this challenge using the concrete example of our recent measurement of the gravitational field of a 1mm gold sphere, the smallest source mass to date in table-top gravity experiments.
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