Events List for the Academic Year
Event Time:
Friday, October 5, 2018 | 8:30 am - 10:30 am
Event Location:
Room 318, Hennings Building
Add to Calendar
2018-10-05T08:30:00
2018-10-05T10:30:00
Departmental Oral Examination (Thesis Title: “Decay Spectroscopy of Neutron-Rich Cadmium Around the N = 82 Shell Closure")
Event Location:
Room 318, Hennings Building
Event Time:
Thursday, October 4, 2018 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar
2018-10-04T16:00:00
2018-10-04T17:00:00
Paradigms 2.0: Supporting Collaborative Departmental Change
Event Information:
The Paradigms in Physics program began 20 years ago at Oregon State University. In those two decades, we not only completely restructured the content trajectory for majors to be more aligned with how professionals think about the content, but we also designed many course activities which reflect not only our own education research but also results from other PER and DBER groups. In the past two years, we have chosen to revise and update the program to reflect new research interests among department faculty and to allow us to incorporate holistic changes that could not be addressed iteratively. Along the way, we have been documenting and studying our change process. We will share insights from the change process about how to support faculty in collaboratively implementing curriculum reform based on education research.
Event Location:
Hennings 201
Event Time:
Thursday, October 4, 2018 | 2:00 pm - 3:00 pm
Event Location:
TRIUMF Auditorium
Add to Calendar
2018-10-04T14:00:00
2018-10-04T15:00:00
Physics of Superheavy Nuclei
Event Information:
Where does the Periodic Table end? What is the mass of the heaviest atomic nucleus? With the addition of four new elements in 2015, the seventh row of the table is now complete, but answers to such basic questions remain elusive. I will present a brief review of the current status of the topic, and recent controversies in the field, including the failure to directly determine the atomic number, Z, and mass number, A, of many of the newly discovered superheavy isotopes. Then I will turn to describing new efforts to address outstanding issues. For instance, while the single-particle structure is vital to understanding the stability of the heaviest elements, the alpha decay and fission processes ultimately determine how long a nucleus will survive. Recent observations, and theoretical descriptions, suggest that metastable states, which can have substantial hindrance to fission and favor decay via alpha emission, may be much longer lived than the ground state of the same nucleus. Such results have tremendous implications for how far we may be able to push the experimental studies of the heaviest elements.
Event Location:
TRIUMF Auditorium
Event Time:
Wednesday, October 3, 2018 | 3:00 pm - 4:00 pm
Event Location:
Henn 318
Add to Calendar
2018-10-03T15:00:00
2018-10-03T16:00:00
Many-body quantum chaos of ultracold atoms in a quantum ratchet
Event Information:
There are now over 300 quantum simulators on at least 10 separate architectures with long coherence times and controlled dynamics. These experimental systems have generated tremendous excitement about driven interacting quantum systems resulting in physics ranging from time crystals to dynamical many-body localization. The quantum ratchet adds a new feature to periodic driving: a preferred direction in both time and space, i.e., parity and time-reversal symmetry-breaking. By studying weakly interacting ultracold bosons in a quantum ratchet on a ring in position, momentum, and Floquet representations, we demonstrate the limits of known measures of quantum chaos in a system with a clearly defined and rather famous semiclassical or mean-field limit, and moreover supporting experiments. We show that the usual Wigner-Dyson statistics used to identify chaos are smeared out as we couple non-resonant modes into the drive. In contrast, the entropy of entanglement, condensate depletion, and inverse participation ratio all serve as accurate alternate identifiers for the chaotic regime in which the current on the ring flip-flops with a positive Lyapunov exponent in the mean-field limit. The dimension of the strange attractor is found to depend on the local vs. global nature of the observables. Moreover, the growth of depletion indicates mean field theory breaks down at realistic experimental times scaling polynomially as in the chaotic regime. This study opens the door to beyond single-frequency many-body Floquet physics showing many surprises and subtleties in both the quantum many-body dynamics and the mean-field limit (or lack thereof). Our prediction of a concrete time at which depletion grows is experimentally observable via an interference experiment. The dynamics and emergent structure of higher order correlators remains an especially intriguing avenue of exploration as we find that, contrary to oft-stated popular opinion, chaos, at least in the quantum ratchet, does not lead to high entanglement.
References:
Marc Andrew Valdez, Gavriil Shchedrin, Martin Heimsoth, Charles E. Creffield, Fernando Sols, and Lincoln D. Carr, "Many-body Quantum Chaos and Entanglement in a Quantum Ratchet," Phys. Rev. Lett., v. 120, p. 234101 (2018).
Marc Andrew Valdez, Gavriil Shchedrin, Fernando Sols, and Lincoln D. Carr, "Layered Chaos in Mean-field and Quantum Many-body Dynamics," to be submitted (2018).
M. Heimsoth, D. Hochstuhl, C. E. Creffield, L. D. Carr, and F. Sols, "Effective Josephson dynamics in resonantly driven Bose-Einstein condensates," New J. Phys., New J. Phys. v. 15, p. 103006 (2013).
M. Heimsoth, C. E. Creffield, L. D. Carr, and F. Sols, "Orbital Josephson effect and interactions in driven atom condensates on a ring," New J. Phys., v. 14, p. 075023 (2012).
Event Location:
Henn 318
Event Time:
Tuesday, October 2, 2018 | 7:30 pm - 9:00 pm
Event Location:
Hennings Building - RM 202 (6224 Agricultural Road) UBC
Add to Calendar
2018-10-02T19:30:00
2018-10-02T21:00:00
The Quantum Way of Doing Computations
Event Information:
Since the mid-1990s, we have seen how computers and many of their applications can be enhanced using quantum physics. This is timely since "Moores law", for the continuing development of conventional computers, will not apply to ever-smaller electronic components governed by quantum physics. All computations, in our heads or in computational devices, rely on the real physical processes of data input, data representation in a memory, data manipulation using algorithms and finally, data output. Building a quantum computer we then require quantum bits (qubits) as storage sites for quantum information, quantum registers and quantum gates for data handling and processing and the development of quantum algorithms. I will review the basic principles of quantum computation, and show how strings of trapped ions can be used to build a quantum information processor, and do basic computations. Routes towards a scalable quantum computer will be discussed.
Event Location:
Hennings Building - RM 202 (6224 Agricultural Road) UBC
Event Time:
Monday, October 1, 2018 | 4:00 pm - 5:00 pm
Event Location:
AMPEL 311
Add to Calendar
2018-10-01T16:00:00
2018-10-01T17:00:00
Recent results of REXS and RIXS experiments on quantum materials
Event Location:
AMPEL 311
Event Time:
Monday, October 1, 2018 | 3:00 pm - 4:15 pm
Event Location:
Hennings 318
Add to Calendar
2018-10-01T15:00:00
2018-10-01T16:15:00
Massive black holes in the smallest galaxies
Event Information:
Supermassive black holes are thought to exist in the centres of most massive galaxies and their masses have been found to correlate strongly with the properties of their host galaxies like overall luminosity or central velocity dispersion. Yet it is unknown what processes have established these correlations and if and how they continue towards lower mass systems. In my talk I will present results from our search for massive black holes in ultra-compact dwarf galaxies in nearby galaxies and in massive globular clusters of the Milky Way.
Please join us before the Colloquium in Hennings 318 for coffee, tea and snacks at 2:45 pm
Event Location:
Hennings 318
Event Time:
Friday, September 28, 2018 | 9:00 am - 11:00 am
Event Location:
Room 309, Hennings Building
Add to Calendar
2018-09-28T09:00:00
1998-09-28T11:00:00
Final PhD Oral Examination (Thesis Title: “Development of Trajectory-Based Techniques for the Stereotactic Volumetric Modulated Arc Therapy of Cranial Lesions”)
Event Information:
Abstract:
Introduction: Stereotactic Radiosurgery is the delivery of a large, highly focused radiation dose to well defined targets in the brain. This thesis explores linac-based inverse planning algorithms that can be implemented to improve the dosimetric and delivery performance of Volumetric ModulatedArc Therapy treatments for these indications.
Methods: In this work, algorithms for Couch-Gantry, and Collimator-Gantry trajectory optimization were developed. Treatment plans calculated with
these algorithms were compared dosimetrically to conventional methods used for treatment planning. Additionally, the clinical feasibility of the
methods developed were tested by performing end-to-end patient specific Quality Assurance on prospective treatments and by developing machine specific quality assurance for the intra-treatment movement of the couch and collimator.
Results: This thesis introduces a robust method for optimizing the trajectory of the couch by delivering treatments along patient generalized trajectories. These treatments were able to dosimetrically outperform Dynamic Conformal Arcs, and had higher delivery efficiency than multi-arc
volumetric modulated arc therapy. Similarly, collimator trajectory optimization was shown to reduce the dose bath when compared with the clinical standard of care. These methods were shown to be safe for delivery using phantom verification studies.
Conclusion: This thesis outlines methods for stereotactic radiosurgery which show dosimetric improvement over previous methodology and are
clinically feasible.
Event Location:
Room 309, Hennings Building
Event Time:
Thursday, September 27, 2018 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar
2018-09-27T16:00:00
2018-09-27T17:00:00
How helices bend, curve and stretch: does physical intuition help us understand protein mechanics?
Event Information:
Our group is investigating the mechanics of a key structural protein, collagen, which is comprised of three chains that coil to make a triple helix. Collagen is the fundamental structural protein in vertebrates and is widely used as biomaterial, for example as a substrate for tissue engineering. In spite of its prevalence and mechanical importance in biology, the mechanics of collagen is surprisingly unresolved. In this talk, I will focus on its flexibility and its stress response, why these properties are important and contentious, and how my group’s work has helped to address some of the discrepancies in the literature. I’ll describe our experimental approaches, which use image-analysis software and statistics to analyse atomic-force microscopy images of single collagen proteins, and which use a high-throughput single-molecule force spectroscopy instrument we’ve built, the mini-radio centrifuge force microscope (MR.CFM), to measure collagen’s response to load. Finally, we will see whether physical intuition and models correctly predict the mechanical response of this key protein.
Event Location:
Hennings 201
Event Time:
Thursday, September 27, 2018 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar
2018-09-27T16:00:00
2018-09-27T17:00:30
How helices bend, curve and stretch: does physical intuition help us understand protein mechanics?
Event Information:
Our group is investigating the mechanics of a key structural protein, collagen, which is comprised of three chains that coil to make a triple helix. Collagen is the fundamental structural protein in vertebrates and is widely used as biomaterial, for example as a substrate for tissue engineering. In spite of its prevalence and mechanical importance in biology, the mechanics of collagen is surprisingly unresolved. In this talk, I will focus on its flexibility and its stress response, why these properties are important and contentious, and how my group’s work has helped to address some of the discrepancies in the literature. I’ll describe our experimental approaches, which use image-analysis software and statistics to analyse atomic-force microscopy images of single collagen proteins, and which use a high-throughput single-molecule force spectroscopy instrument we’ve built, the mini-radio centrifuge force microscope (MR.CFM), to measure collagen’s response to load. Finally, we will see whether physical intuition and models correctly predict the mechanical response of this key protein.
Event Location:
Hennings 201
Event Time:
Thursday, September 27, 2018 | 2:00 pm - 3:00 pm
Event Location:
AMPL 311
Add to Calendar
2018-09-27T14:00:00
2018-09-27T15:00:00
Mapping the Calogero model onto the Anyon model
Event Information:
I will first give a review of the thermodynamics of the anyon model and the Lowest Landau Level (LLL) anyon model (i.e. anyons coupled to a strong external magnetic field), in relation to that of the Calogero model and Haldane fractional statistics. Then I will construct explicitly an $N$-body kernel which maps Calogero eigenstates onto anyonic eigenstates (arXiv: 1805.09899).
Event Location:
AMPL 311
Event Time:
Thursday, September 27, 2018 | 2:00 pm - 3:00 pm
Event Location:
TRIUMF Auditorium
Add to Calendar
2018-09-27T14:00:00
2018-09-27T15:00:00
Exploring Symmetry Violations with Free Neutrons
Event Information:
Symmetry principles are basic tenets for our theory of fundamental interactions. While they have been essential in building the theory, it is in their violations were major breakthroughs have often occurred. We will discuss how searches for symmetry violations can play a key role in elucidating the details of the fundamental forces. We will focus on the role of past and future precision measurements using free neutrons.
Event Location:
TRIUMF Auditorium
Event Time:
Monday, September 24, 2018 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar
2018-09-24T15:00:00
2018-09-24T16:00:00
Internal kinematics of globular clusters
Event Information:
With the advent of the Gaia mission, astrometry is experiencing a renaissance. Although Gaia will make important breakthroughs in many different areas, stars in the crowded central fields of globular clusters and at the faint end of the color-magnitude diagram are out of Gaia's reach. However, the stable environment of space makes the Hubble Space Telescope (HST) an excellent astrometric tool. Its diffraction-limited resolution allows it to distinguish and measure positions and brightnesses for faint stars all the way to the center of most globular clusters. I will present recent results from our HST-based, high-precision proper-motion analysis of Galactic globular clusters, with particular focus on kinematic differences among their multiple stellar populations.
Please join us before the Colloquium in Hennings 318 for coffee, tea and snacks at 2:45 pm
Event Location:
Hennings 318
Event Time:
Thursday, September 20, 2018 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar
2018-09-20T16:00:00
2018-09-20T17:00:00
Polarization of the Cosmic Gravitational Wave Background
Event Information:
The Cosmic Gravitational Wave Background (CGB) is a
hypothesized relic radiation field that, if detected, would give us
clues to the earliest moments of the history of the Universe. In this
talk, accessible to students and non-experts, I will describe the
physical processes that can give rise to a CGB, novel features including
a net polarization of the gravitational waves (as distinct from the
polarization of cosmic microwave background photons), and methods of
detection. I will also discuss the ability of the proposed Laser
Interferometer Space Antenna, LISA, to detect the CGB.
Event Location:
Hennings 201
Event Time:
Thursday, September 20, 2018 | 2:00 pm - 3:00 pm
Event Location:
Hennings 318
Add to Calendar
2018-09-20T14:00:00
2018-09-20T15:00:00
Computing Resonant Inelastic X-Ray Scattering Spectra Using The Density Matrix Renormalization Group Method
Event Information:
Over the past decade, Resonant Inelastic X-Ray Scattering spectroscopy (RIXS) has been established as a powerful technique to study the energy-momentum structure of charge, orbital, lattice, and magnetic excitations of strongly correlated materials.
The computation of RIXS spectra starting from model Hamiltonians is often a formidable task because of the absence of accurate many-body tools,
particularly when many orbitals are active. In most cases, exact diagonalization (ED) techniques are used which restricts clusters to a relatively small size.
In this talk, I will present a method for computing RIXS spectra in one-dimensional systems using the Density Matrix Renormalization Group Method.
With this new procedure, I computed the low-energy magnetic excitations observed in Cu L-edge RIXS for the challenging corner shared
CuO_4 chains on cluster sizes well beyond state-of-the-art ED techniques, using both multi-orbital and downfolded t-J model Hamiltonians.
Finally, I will discuss the implications of the results for experiments and outline future directions of research.
Event Location:
Hennings 318
Event Time:
Monday, September 17, 2018 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar
2018-09-17T15:00:00
2018-09-17T16:00:00
Probing planetary interior structure and processes with high-precision rotation measurements
Event Information:
Profound developments in our understanding of the Earth, Moon, and other planetary bodies have been enabled by rotation studies. I will describe the application of a new Earth-based radar technique that enables high-precision measurements of planetary spin states and provides powerful probes of planetary interior structure and processes.
Observations of radar speckle patterns tied to the rotation of Mercury establish that the planet exhibits periodic variations in rotation period or length of day. The amplitude of the oscillations show that the mantle of Mercury is decoupled from a molten outer core. These data enable precise estimates of Mercury's moment of inertia and the size of its core.
Observations of Venus show that its spin period is not constant. The length of day exhibits ~70 ppm variations that are consistent with percent-level changes in atmospheric angular momentum transferred to the solid planet. Monitoring these fluctuations provides important constraints on the atmospheric dynamics of Venus, which is key to elucidating its superrotation and the generation of recently discovered planetary-scale structures in the atmosphere. The radar observations provide the most realistic near-term prospect of measuring Venus's moment of inertia and the size of its core.
Measurements of Europa's obliquity suggest that the ice shell is decoupled from the interior, strengthening the case for a global subsurface ocean. The amplitude of the oscillations in length of day depends on the rheology and thickness of the ice shell, perhaps the most important determinants of Europa's astrobiological potential.
Event Location:
Hennings 318
Event Time:
Friday, September 14, 2018 | 6:00 pm - 7:00 pm
Event Location:
UBC Life Building
Add to Calendar
2018-09-14T18:00:00
2018-09-14T19:00:00
Our amazing Universe: astronomical revelations and new mysteries
Event Information:
Dr. Francois Bouchet will describe current observations that precisely constrain the nature of the Cosmos in which we live, leading to radical ideas for the origin of the structures within it. These touch on questions such as: How did the Universe originate? What is it made of? Why is it the way that it is? What is the nature of the Dark Matter and Dark Energy that dominate the Universe? How do we actually learn about these? And what are the new mysteries that our observations are revealing?
Francois R. Bouchet is a French astronomer specializing in physical cosmology, including formation of large scale structures and the study of the remnant radiation from the Big Bang. His research combines theoretical and numerical studies with analysis of data from space- and ground-based telescopes. He is based at the lnstitut d'Astrophysique de Paris, where he has served as overseer of the data analysis effort for the Planck satellite mission. Dr. Bouchet is a Research Director of the CNRS and serves as President of the Scientific Council of the National Cosmology Program.
Event Location:
UBC Life Building
Event Time:
Thursday, September 13, 2018 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar
2018-09-13T16:00:00
2018-09-13T17:00:00
2-dimensional phase separation in cell membranes: How yeast harness physics to organize proteins and lipids
Event Information:
(No prior knowledge of biology is required for this talk!) For decades, scientists have argued about how living cell membranes acquire and maintain regions enriched in particular lipid and protein types. One of the more contentious theories has been that lipids and proteins spontaneously phase separate within the plane of the membrane to create liquid regions that differ in their composition. Physicists have long observed this type of demixing in simple artificial membranes. Clear identification of the same transition in a living biological system has heretofore been elusive. Here, by directly imaging micron-scale membrane domains of yeast organelles both in vivo and cell-free, we show that domains merge quickly, consistent with fluid phases. Moreover, the domains appear at a distinct miscibility transition temperature. Hence, large-scale membrane organization in living cells under physiologically relevant conditions can be controlled by tuning a single thermodynamic parameter. Interesting physical questions underlie this phenomenon. For example, asking how domains are coupled across the two faces of the membrane led to the first measurement of the interleaflet coupling parameter. Similarly, asking how sub-micron composition fluctuations might arise in a lipid membrane near a critical point led to our determination of the membrane’s effective critical dynamic exponent -- the first successful systematic measurement of this fundamental physical parameter in any 2dimensional Ising system with conserved order parameter. Asking how groups of lipids diffuse within a membrane led to our measurement of growth exponents for membrane domains. These projects were recently highlighted by Physics Today (Feb. 2018) and published in The Biophysical Journal (2017, 113:2425-2432; 2015; 109:2317-2327; and 2013, 105:444-454) and Physical Review Letters (2012, 108:265702).
Event Location:
Hennings 201
Event Time:
Thursday, September 13, 2018 | 12:00 pm - 2:00 pm
Event Location:
CEME 1210
Add to Calendar
2018-09-13T12:00:00
2018-09-13T14:00:00
Departmental Oral Examination (Thesis Title: “Emergent Spacetime in Matrix Models")
Event Information:
Abstract:
We study the noncommutative geometry associated to matrices of N quantum dots in the matrix models. The earlier work established a surface embedded in flat R^3 from three Hermitian matrices. We construct coherent states corresponding to points in the emergent geometry and find the original matrices determine not only shape of the emergent surface, but also a unique Poisson structure. We prove that commutators of matrix operators correspond to Poisson brackets. Through our construction, we can realize arbitrary noncommutative membranes embedded in R^3.
We further conjecture an embedding operator which assigns, to any 2n + 1 Hermitian matrices, a 2n-dimensional hypersurface in flat (2n + 1)-dimensional Euclidean space. This corresponds to precisely defining a fuzzy D(2n)-brane corresponding to N D0-branes. Points on the hypersurface correspond to zero eigenstates of the embedding operator, which have an interpretation as coherent states underlying the emergent noncommutative geometry. Using this correspondence, all physical properties of the emergent D(2n)-brane can be computed.
Many works have been done in exploring the geometry emerged from the matrix configuration, but they do not always produce consistent results.
We apply two types of point probe methods and the supergravity charge density formula on the generalized fuzzy sphere S^2(so(4)) . Its tangled structure challenges the applicability of the probing methods. We propose to disentangle blocks of S^2(so(4)) regarding the geometrical symmetry and retrieve S^2(so(4)) as a thick two sphere with coherent layers consistently in three methods.
The Yang-Mills matrix model with mass term representing IR cutoff on the effective radius generates remarkable spherical solutions of the emergent universe, but it is unsolvable, unlike matrix models dominated by the Gaussian potential. After imposing the spherical topology, we approach the model approximately by coarse-graining the dimension of matrices and find the free energy satisfies the Callan-Symanzik like renormalization group equation and reproduces 2D quantum gravity near the fixed point of the running mass. Among classical solutions of generalized fuzzy spheres, the critical sphere has its mass at the fixed point within a range of matrix dimensions for a given effective radius cutoff.
Event Location:
CEME 1210
Event Time:
Thursday, September 13, 2018 | 2:00 am - 3:00 am
Event Location:
AMPL 311
Add to Calendar
2018-09-13T02:00:00
2018-09-13T03:00:00
From solids with topology to black holes and back
Event Information:
Inclusion of topological phenomena in condensed matter physics over the past 10 years ushered a revolution in this field. As a result of the new theoretical insights entire classes of materials with exotic properties have been discovered, including topological insulators, Dirac and Weyl semimetals as well as topological superconductors containing Majorana fermions. In this talk I will give a brief review of these developments and discuss an intriguing connection noticed recently by Kitaev between one such topological system – the Sachdev-Ye-Kitaev model – and the horizon of a black hole. This connection furnishes a rare example of holographic duality between a solvable quantum-mechanical model and Einstein gravity, and may have simple physical realization in a tabletop experiment.
Event Location:
AMPL 311