Events List for the Academic Year
Event Time:
Monday, March 6, 2023 | 3:00 pm - 4:00 pm
Event Location:
HENN 318
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2023-03-06T15:00:00
2023-03-06T16:00:00
Baryon Cycles in the Biggest Galaxies
Event Information:
Abstract:
The universe’s biggest galaxies have both vast atmospheres and supermassive central black holes. Coupling between those two components of a large galaxy couple regulates the galaxy’s star formation rate. Models of interactions between a supermassive black hole and the large-scale atmosphere suggest that the energy released as cold gas clouds accrete onto the black hole suspends the atmosphere in a state that is marginally stable to formation of cold clouds.
A growing body of observational evidence indicates that many massive galaxies, ranging from the huge central galaxies of galaxy clusters down to our own Milky Way, are close to that marginal state. The gas supply for star formation within a galaxy in such a marginal state is closely tied to the galaxy's central potential well, as traced by the central velocity dispersion of its stars. Those findings suggest that energy released during black-hole accretion shuts down star formation when the central potential well depth exceeds a critical value determined by the galaxy’s supernova heating rate.
Bio:
I’m currently an astronomy professor at Michigan State University. My journey here started in suburban Philadelphia. I graduated from Cheltenham High School in 1979 and from Princeton in 1983, with an A.B. in Astrophysical Sciences. My Ph.D. in Astrophysics (1990) is from the University of Colorado. Then came three years as a Research Fellow at Caltech, two more as a Hubble Fellow at Johns Hopkins, and eight as an astronomer at the Space Telescope Science Institute, working on the Hubble Space Telescope project, before Michigan State brought me on board in 2003.
Learn more:
View Dr. Voit's personal website here.
View Dr. Voit's Michigan State faculty webpage here.
Event Location:
HENN 318
Event Time:
Monday, March 6, 2023 | 11:00 am - 12:00 pm
Event Location:
HENN 318
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2023-03-06T11:00:00
2023-03-06T12:00:00
Probing fundamental physics by mapping the millimeter and submillimeter sky
Event Information:
Abstract:
Cosmology has transformed from a field of speculation to precision science as a result of a wealth of data from sensitive instruments. In particular, precise observations of the cosmic microwave background (CMB) have revolutionized our understanding of the Universe. Despite the success of the standard model of cosmology (ΛCDM) in describing much of the cosmos with just six parameters, many fundamental questions remain unresolved. Are there primordial gravitational waves? Are there new light relic particles? How will the current cosmological tensions be resolved? Improved mapping of the millimeter and submillimeter sky will help address these questions. I will highlight recent results from the Atacama Cosmology Telescope (ACT), and describe how the new ACT maps will advance our understanding of the Universe beyond Planck. I will also present recent progress on CCAT-prime and Simons Observatory that are paving the way for CMB-S4 in pursuit of next generation cosmology.
Bio:
I am an NSF Astronomy and Astrophysics Postdoctoral Fellow at Cornell University. My primary research interest is on understanding the formation and evolution of our universe through building sensitive instruments to make precise measurements and applying modern data analysis techniques to them.
On the experimental side I am developing novel instruments using MKID arrays for the CCAT-prime project. MKIDs are a promising detector technology for making future sub-mm measurements, but they have yet to be demonstrated from the best observing sites in the world such as that to be used by CCAT-prime. As a graduate student at Princeton University I worked on a different detector technology, TES arrays, for the Atacama Cosmology Telescope. In addition, I investigated infrared blocking filters, a crucial component in mm and sub-mm telescope receivers.
I continue to analyze data from the Atacama Cosmology Telescope. Recently, the cosmological data analysis I led resulted in a new precise measurement of the age and expansion rate of our universe (covered on Gizmodo!). I’ve also worked on searching for B-modes and characterizing foreground emission for measuring B-modes. This led to a definitive measurement of the correlation of the polarized thermal dust and synchrotron radiation from the Milky Way.
Learn More:
View Steve's faculty webpage from Cornell University here
See his homepage here
Event Location:
HENN 318
Event Time:
Monday, March 6, 2023 | 10:00 am - 11:00 am
Event Location:
HENN 309
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2023-03-06T10:00:00
2023-03-06T11:00:00
X-ray Insights into the Connection between Quenching of Star Formation and Galaxy Stellar Velocity Dispersion
Event Information:
Abstract:
There is a surprisingly tight correlation between galaxies with quenched star formation and their central velocity dispersion, which also correlated with the central black hole's mass. Those correlations suggest that the central black hole is the culprit. However, radio and X-ray observations of these galaxies show that the black hole's considerable energy production can bypass the galaxy and thermalize at distances tens of kiloparsecs from the galaxies' stars. The circumgalactic medium (CGM) may therefore be what connects black hole feedback with quenching of star formation. The CGM can be difficult to observe, but X-ray observations have yielded important clues about the how black holes and the CGM are connected.
We have proposed a "valve" model for that connection, whereby the black hole lifts the CGM, lowering the circumgalactic pressure and allowing two distinct states for the galaxy: a wind-dominated mode where winds from type 1a supernovae suppress gas cooling, and a precipitation-dominated mode where cool gas can rain from the hot CGM. This cold "multi-phase" gas can feed the black hole and trace amounts of star formation, completing and sustaining the feedback cycle that keeps a galaxy quenching. The central velocity dispersion - the observational signature of the central gravitational potential - may determine which state prevails in each galaxy.
We will discuss what the X-ray observations have shown so far, and what future X-ray and UV observations may unlock.
Bio:
Megan Donahue studies clusters of galaxies. Cluster evolution tells us about the matter density of the universe, because the formation of galaxy clusters is governed by gravitational physics. She pays particular attention to how clusters are found, because any bias in finding clusters can lead to a bias in our conclusions about them. She also studies the metallicity, distribution, and physics of intergalactic gas. Is this really where most of the baryons are hiding? Her work includes models and observational tests of cooling flows in the gas within clusters. Strange things are afoot in cluster cores and she would like to sort it out.
Professor Donahue was named a Fellow of the American Physical Society in October 2016 for "advanced cosmological observations and analyses of galaxy clusters, and of the relationship between the thermodynamic state of circumgalactic gas around massive galaxies, the triggering of active galactic nucleus feedback, and the regulation of star formation in galaxies" after nomination by the APS Division of Astrophysics.
Professor Donahue was elected as President of the American Astronomical Society (AAS) in 2017.
Learn More:
View Dr. Donahue's faculty webpage here
View her Home page here
Event Location:
HENN 309
Event Time:
Thursday, March 2, 2023 | 4:00 pm - 5:15 pm
Event Location:
HENN 201
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2023-03-02T16:00:00
2023-03-02T17:15:00
3 Minute Thesis Competition, Physics and Astronomy Heat
Event Information:
Three Minute Thesis (3MT)
*On Thursday March 2, 2023 from 4:00 - 5:15pm during the Department Colloquium, in HENN 201*
The Three Minute Thesis (3MT) is an academic competition that assists current graduate students with fostering effective presentation and communication skills. Participants have just three minutes to explain the breadth and significance of their research project to a non-specialist audience. Over 200 universities participate in this fun, highly informative and very entertaining event. UBC was one of the first Universities in North America to host a 3MT competition.
Read more about the PHAS Heat of 3MT.
Register for the 2023 UBC Physics and Astronomy Heat of 3MT.
For full information, schedule, rules, eligibility, coaching sessions, judging criteria etc, see UBC 3 Minute Thesis.
Please note that two of our recent PHAS finalists who placed in the top 3 (and won cash prizes!) in the past 4 years took advantage of the 3MT Personal Presentation Feedback Sessions (20 min by appointment). Register for Feedback Session.
Event Location:
HENN 201
Event Time:
Thursday, March 2, 2023 | 11:00 am - 12:00 pm
Event Location:
HENN 318
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2023-03-02T11:00:00
2023-03-02T12:00:00
New directions for the detection of light dark matter
Event Information:
Abstract:
Dark matter remains one of the central mysteries of cosmology and particle physics. Here, I introduce a new set of strategies in the search for the universe's missing mass. I will present a series of recent theoretical developments that predict that molecules and nano-materials are optimal targets to use in next-gen detectors looking for dark matter beyond the weak scale. I will show that molecular detectors can be sensitive to the direction of the dark matter wind, producing daily-modulating signals. Additionally I will show that semiconducting nano-crystals (quantum dots) can produce inherently low-noise signals following dark-matter induced excitations. Finally, I will advocate for the further development of the theoretical formalism underlying these novel strategies and comment on emerging collaborations that aim to rapidly develop and deploy these promising detectors.
Bio:
Carlos Blanco completed his PhD at the Kavli Institute for Cosmological Physics at the University of Chicago, and is currently working at Princeton University as a postdoctoral Research Associate.
Learn More:
View Carlos' web profile here
See past publications via INSPIRE website here
See a YouTube video of Carlos speaking on "New Directions in Dark Matter Direct Detection" from March 02, 2022
Event Location:
HENN 318
Event Time:
Thursday, March 2, 2023 | 10:00 am - 11:00 am
Event Location:
AMPL 311
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2023-03-02T10:00:00
2023-03-02T11:00:00
The Quantum Twisting Microscope
Event Information:
Abstract: In this talk, I will present a new type of scanning probe microscope, the Quantum Twisting Microscope (QTM), capable of performing local quantum interference measurements at a twistable interface between two quantum materials. Its working principle is based on a unique tip made of an atomically-thin two-dimensional material. This tip allows electrons to coherently tunnel into a sample at many locations at once, with quantum interference between these tunneling events, making it a scanning electronic interferometer. With an extra twist degree of freedom, our microscope becomes a momentum-resolving local probe, providing powerful new ways to study the energy dispersions of interacting electrons. I will present various experiments performed with this microscope, demonstrating quantum interference at room temperature, probing the conductance of in-situ twisting interfaces, and imaging local energy dispersions of graphene and twisted bilayer graphene.
Speaker Bio: I am a postdoctoral researcher working at the Weizmann Institute of Science with Prof. Shahal Ilani. I completed my Ph.D. with Prof. Andre Geim and Prof. Irina Grigorieva at the University of Manchester, UK. My research focuses on using unique scanning probe microscopes to visualize the electronic properties of 2D materials and vdW heterostructures.
Event Location:
AMPL 311
Event Time:
Wednesday, March 1, 2023 | 11:00 am - 12:00 pm
Event Location:
HENN 318
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2023-03-01T11:00:00
2023-03-01T12:00:00
How do the most luminous black holes accrete and expel gas?
Event Information:
Abstract:
The gravitational pull of a black hole attracts gas and forms a physical laboratory whose extreme conditions cannot be replicated on Earth. The infalling gas forms an accretion disk where the interplay between hydromagnetic processes and the warping of space-time releases gravitational energy in the form of radiation, relativistic jets, and winds. It is likely that most gas falls into supermassive black holes when the accretion rate approaches the Eddington limit (L=Ledd), at which point radiation pressure overcomes gravity. To date, our knowledge of such `luminous’ black hole accretion disks mostly relies on semi-analytical models, supplemented by a very limited set of numerical simulations.
In my talk I will discuss new insights gained from the first radiative general relativistic magnetohydrodynamics (GRMHD) simulations of luminous accretion disks. I will demonstrate that magnetic fields lead to the formation of a hot corona and that misalignment between the disk and black hole spin axis can explain quasi-periodic oscillations, which have remained a mystery for over 30 years.
I will finish my talk by discussing the opportunities the next-generation of GRMHD simulations will bring in addressing the origin of non-thermal radiation, cosmic rays, and neutrinos from accreting black holes.
Bio:
Matthew Liska is a computational astrophysicist with an interdisciplinary interest in astrophysics, plasma physics and computation. He is the main developer of the world's first GPU accelerated GRMHD code ("H-AMR") which he uses to study accretion onto compact objects such as black holes. He completed his PhD in 2019 at the University of Amsterdam and is now a John Harvard & ITC Fellow at Harvard CFA.
Learn More:
See Matthew's webpage here
Event Location:
HENN 318
Event Time:
Tuesday, February 28, 2023 | 1:00 pm - 3:00 pm
Event Location:
UBC Centre for Brain Health Room 3402, Vancouver
Zoom: https://ubc.zoom.us/j/62544295867?pwd=eURLUHJ3K1V6MVpETVpWTVppOGJOQT09
Meeting ID: 625 4429 5867
Passcode: 682315
Zoom: https://ubc.zoom.us/j/62544295867?pwd=eURLUHJ3K1V6MVpETVpWTVppOGJOQT09
Meeting ID: 625 4429 5867
Passcode: 682315
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2023-02-28T13:00:00
2023-02-28T15:00:00
Advances in Quantitative Magnetic Resonance Imaging of Myelin
Event Information:
Myelin water imaging (MWI) is a quantitative magnetic resonance imaging (MRI) technique generally regarded as the most rigorous approach for non-invasive, in-vivo measurement of myelin content.
Although MWI has proven valuable for the study of development, aging, disease, injury, genetics, and fundamental biology in the central nervous system, the power of its insights hinge on accurate characterization of normative values. To that end, we used MWI data from 100 adults (age 20-78) to create an optimized, unbiased myelin atlas and characterize how myelin content changes throughout the adult life span; an invaluable, openly available reference for future studies.
In practice, lengthy acquisition times have limited the utility of MWI and often lead to alternative approaches being used to acquire surrogates for MWI. To compare the traditional multi-echo T2 relaxation and alternative steady-state MWI approaches, we created multivariate brain and spinal cord atlases and found an approximately linear relationship between myelin estimates, which broke down in the presence of unique relaxation times (spinal cord, tissue affected by disease pathology). This work will improve retrospective interpretation, and guide future design, of MWI studies.
Next, we addressed lengthy MWI acquisition times using conventional compressed sensing before ultimately introducing the Constrained, Adaptive, Low-dimensional, Intrinsically Precise Reconstruction (CALIPR) framework. Drastically improved reconstruction performance allowed whole-brain MWI to be acquired using a previously unattainable sequence (fully sampled acquisition time 2h:57m:20s) in only 7m:26s with CALIPR (acceleration factor 23.9, 4.2% of the dataset). Reproducibility experiments demonstrated excellent precision, and CALIPR provided markedly increased sensitivity to demyelinating disease pathology (the hallmark application for myelin imaging). We implemented CALIPR for MWI of brain and spinal cord, and for two of the three largest MRI manufacturers. The CALIPR framework provides increased acceleration, precision, and sensitivity for MWI, and could be similarly transformative for other quantitative MRI applications.
Finally, we implemented CALIPR on an ultra-low field (0.064T) portable, point-of-care MRI scanner to acquire accurate, quantitative T2 mapping data in <10 minutes. In combination with the accessible, low-cost imaging enabled by this platform, this work could help revolutionize the care of neurological disorders by enabling frequent, quantitative assessment of subtle tissue changes.
Event Location:
UBC Centre for Brain Health Room 3402, Vancouver
Zoom: https://ubc.zoom.us/j/62544295867?pwd=eURLUHJ3K1V6MVpETVpWTVppOGJOQT09
Meeting ID: 625 4429 5867
Passcode: 682315
Event Time:
Monday, February 27, 2023 | 3:00 pm - 4:00 pm
Event Location:
HENN 318
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2023-02-27T15:00:00
2023-02-27T16:00:00
Unexpected Outbursts from Massive Stars
Event Information:
Abstract:
This talk will focus on two somewhat unusual types of shock dynamics associated with core-collapse supernovae:
1. "Bells, not whistles": Some massive stars appear to undergo shock-driven outbursts before their cores collapse. I will show that nonlinear acoustics rules out a standard explanation for how these events are driven, a result that deepens the mystery of their origin.
2. "Flares from Asphericity": Compact supernovae have a unique potential to make especially fast, even relativistic, surface flows, even if they are spherical. But they often are not spherical, and this fact has complicated consequences. I will discuss whether one consequence -- the collision of ejecta streams -- creates a new class of observable flare.
Bio:
I am a professor of theoretical astrophysics at the University of Toronto, working on the fluid dynamics of gravitational collapse and energetic feedback in:
- star and star cluster formation,
- molecular cloud evolution and the interstellar medium,
- black hole formation and accretion,
- stellar tidal disruptions,
- supernovae, gamma-ray bursts, and related transients.
Learn more:
See Dr. Matzner's website here
Enjoy his list of "Resources for the ambitious undergraduate or beginning graduate researcher in Astronomy & Astrophysics" here!
Event Location:
HENN 318
Event Time:
Monday, February 27, 2023 | 11:00 am - 12:00 pm
Event Location:
HENN 318
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2023-02-27T11:00:00
2023-02-27T12:00:00
Exploring Exoplanet Populations with Kepler, TESS, and Beyond
Event Information:
Abstract:
Exoplanet surveys such as Kepler and TESS have been spectacularly successful in identifying thousands of planets with breathtaking diversity. These discoveries help place the Solar System in context and inform our understanding of how planets form and evolve. Finding large numbers of planets also enables statistical studies of the exoplanet population, through which we can uncover which types of planets are more common than others and find correlations between planet abundance and the properties of stars. Such exoplanet demographic studies are key for constraining planet formation and evolution theories and for predicting the science yields of future missions, especially time-critical surveys that will attempt to detect and characterize potentially habitable, Earth-like planets around Sun-like stars. I will highlight my contributions to the field of demographics, from my past work on large and small planet populations with Kepler and its implications for the search for other Earths, to my current work with TESS to significantly expand our understanding of planet populations around more diverse stellar samples than were probed by Kepler. Finally, I will identify a set of important open questions that remain to be answered and outline my future goals to push the field of demographics to new frontiers.
Bio:
I am a TESS postdoctoral associate at MKI. I received my PhD in Astronomy from the University of British Columbia in 2020.
My research is primarily focused on the detection of transiting exoplanets and the statistical determination of exoplanet demographics. For my PhD, I developed an independent pipeline to search archival Kepler data for new exoplanets, and estimated exoplanet occurrence rates from my planet catalogue including the abundance of potentially habitable planets around Sun-like stars. I am particularly interested in improving techniques for deriving and modeling exoplanet occurrence rates, such as through the application of approximate Bayesian computation and combining constraints from multiple types of surveys and exoplanet detection methods in a joint analysis. I am also interested in developing fully automated vetting pipelines and characterizing catalogue false positive rates.
I am committed to science outreach, and have given dozens of talks, hosted science workshops, and participated in podcasts aimed at the general public, high school students, and university students since I was an undergraduate.
Learn More:
View Michelle's webpage from MIT's Kavli Institute here
Event Location:
HENN 318
Event Time:
Monday, February 27, 2023 | 11:00 am - 12:00 pm
Event Location:
To be confirmed
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2023-02-27T11:00:00
2023-02-27T12:00:00
Neutron star science with gravitational waves
Event Information:
TALK RECORDING AVAILABLE AT: https://drive.google.com/file/d/10NAGUXErm9h3xy59d5tGyJTf_MVsHtSL/view?usp=share_link
Abstract:
LIGO and Virgo have observed half a dozen neutron stars with gravitational waves to date. These observations are revealing information about their uncertain internal structure and composition, and are beginning to provide insight into their astrophysical distribution. I will discuss recent work inferring the properties of ultra-dense matter and characteristics of the neutron star population from binary mergers, as well as opportunities for future discoveries in neutron star science with next-generation gravitational-wave observatories.
Event Location:
To be confirmed
Event Time:
Thursday, February 23, 2023 | 11:00 am - 12:00 pm
Event Location:
HENN 318
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2023-02-23T11:00:00
2023-02-23T12:00:00
Quantum electrodynamic phases in triangular magnetic systems
Event Information:
Abstract:
Quantum electrodynamics in (2+1) D (QED_3) consists of relativistic Dirac fermions strongly interacting with photons. Quantum magnets and electron systems under magnetic fields, meanwhile, represent 2 correlated paradigms in magnetism. We show that from symmetry reasoning, QED_3 emerges as a robust, critical phase both in triangular spin-1/2 magnets (called Dirac spin liquid), and half-filled Chern bands of electrons under periodic magnetic fields.
First triangular lattice Dirac spin liquid is shown to be stable as relevant monopole events are forbidden by symmetries. Furthermore, it is proximate to a plethora of symmetry breaking phases, furnishing a unifying framework for 2d frustrated magnets. Numerical and experimental signatures are discussed.
Next, I will show that QED_3 with 3 Dirac fermion species arises in a simple setup of Dirac materials under periodic magnetic fields with triangular lattice structure. Tuning chemical potential that breaks particle-hole symmetry will drive a transition among exotic incompressible states called fractional Chern insulators. Physical observables, numerical and potential experimental prospects are discussed.
Bio:
Xue-Yang Song obtained her PhD in theoretical condensed matter in 2021 and is currently a Moore postdoctoral fellow at MIT. She studies strongly correlated matter that shows emergent quantum phenomena like fractional excitations and high-temperature superconductivity. She is interested in both developing formal theories and making concrete connections to realistic solid state or synthetic systems. Besides physics, she enjoys cycling and playing with her cat.
Event Location:
HENN 318
Event Time:
Thursday, February 16, 2023 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2023-02-16T16:00:00
2023-02-16T17:00:00
Towards an Exoplanets Demographics Ladder
Event Information:
Abstract:
The NASA Kepler mission has provided its final planet candidate catalogue, the K2 mission has contributed another four years’ worth of data, and the NASA TESS mission has been churning out new planet discoveries at a rapid pace. The demographics of the exoplanet systems probed by these transiting exoplanet missions are complemented by the demographics probed by other techniques, including radial velocity, microlensing, and direct imaging. I will walk through the progress of the Kepler occurrence rate calculations, including some of the outstanding issues that are being tackled. I will present our new results from K2 and TESS, and outline how K2 and TESS will be able to push the stellar parameter space in which we can explore occurrence rates beyond that examined by Kepler. Finally, I will highlight some of the pieces of the larger demographics puzzle - occurrence rate results from the other techniques that probe different stellar and exoplanet regimes - and progress to be made working to join those pieces together.
Bio:
2002: Bachelor of Science (Advanced Studies) in physics and mathematics at Griffith University, Brisbane.
BSc first class honours in Astronomy at the Australian National University, Canberra.
2007: PhD at the University of New South Wales in 2007.
Postdoctoral Research Fellow at the Harvard-Smithsonian Centre for Astrophysics.
As a member of the Kepler Science Team, she won the NASA Group Achievement Award in 2010. She is involved in the planning for the upcoming NASA TESS mission, which will search the whole sky for the nearest planets to Earth. She won the 2018 NASA Exceptional Engineering Achievement Medal for her work on the Kepler planet sample.
Learn More:
See Jessie's TEDXTalk here
See Jessie's faculty webpage from the University of Southern Queensland here
See Jessie's webpage from the NASA Exoplanet Science Institute here
Event Location:
HENN 201
Event Time:
Monday, February 13, 2023 | 3:00 pm - 4:00 pm
Event Location:
HENN 318
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2023-02-13T15:00:00
2023-02-13T16:00:00
Causes and Consequences of Chaos in Planetary Systems
Event Information:
Abstract:
Is the solar system stable? This question has garnered attention from a litany of famous scientists and mathematicians since Isaac Newton but was only properly resolved a little over a decade ago with the advent of computer hardware and algorithms capable of following the dynamical evolution of the planets for billions of years. We now know that the solar system will most likely remain stable for the remainder of the Sun’s main-sequence lifetime, though there is a ~1% chance that Mercury is destabilized and collides with Venus or the Sun.
The surprising fact of the solar system’s dynamically fragile state has led some to speculate that additional planets were present earlier in the system’s history, but they have since been lost to collisions or ejections as their presence resulted in a more rapidly unstable system. Shortly after our modern understanding of the solar system’s long-term stability was established, the number of known exoplanet systems grew dramatically thanks to the NASA Kepler mission. Some evidence suggests that many of these exoplanetary systems are perched on the verge of instability and long-term dynamical evolution plays an important role in shaping their orbital architectures.
The potential for the solar system to exhibit instability is intimately related to the fact that it is a chaotic dynamical system and a more general understanding of chaotic behavior in planetary systems is necessary for determining the role of instabilities in shaping the broader population of exoplanet systems. The need for theoretical advances is especially acute since direct numerical simulations, already challenging in the case of the solar system, are impractical given the large number of exoplanet systems, their uncertain masses and orbital properties, and their much older ‘dynamical’ ages. I will describe some recent results on the causes of chaos and dynamical instability in planetary systems, focusing especially on compact systems of low-mass planets like those discovered by Kepler.
Bio:
I am currently a postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics. My research focuses on understanding gravitational dynamics in planetary systems. I apply this understanding in order to make sense of exoplanet observations such as transit timing and radial velocity measurements. I also work to understand the role of gravitational dynamics in the long-term evolution of planetary systems.
Previously, I was a CfA Fellow at the Harvard-Smithsonian Center for Astrophysics. Before that, I received my PhD in Physics and Astronomy from Northwestern University in 2017.
Learn More:
See Sam Hadden's website here.
Event Location:
HENN 318
Event Time:
Monday, February 13, 2023 | 11:00 am - 12:00 pm
Event Location:
Henn 318
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2023-02-13T11:00:00
2023-02-13T12:00:00
Observational constraints of the core-collapse supernova engine with the gravitational-wave data
Event Information:
TALK RECORDING AVAILABLE AT: https://drive.google.com/file/d/1l4DQfOrOuK3dQUECHt1DjAeEUpj4ovnF/view?usp=share_link
Abstract:
Core-collapse supernovae are violent explosions of massive stars. They are usually brighter than their host galaxies, and astronomers observe them daily. However, the mechanism driving these explosions is still unknown. Gravitational waves and neutrinos are the only means directly probing the central engines of these spectacular events. I will present the results of the search for gravitational waves in the data from the third observing run of LIGO-Virgo. We analyzed the data around the explosion time of supernovae observed optically at distances up to 30 Mpc. We have not found any gravitational waves, so we constrain the properties of the explosion's central engine, such as upper limits on the emitted gravitational wave energy and power. For a population of the analyzed supernovae, we constrain the possible core deformation and exclude parameter space of extreme emission models.
Event Location:
Henn 318
Event Time:
Thursday, February 9, 2023 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2023-02-09T16:00:00
2023-02-09T17:00:00
Quantum Simulation with Ultra-Cold Atoms: Spin-Charge Separation
Event Information:
Abstract:
We employ quantum simulation of interesting electronic materials using ultracold 6 Li atoms, a composite fermion, as stand-ins for the electrons Quantum simulation of this kind takes advantage of the capability to adhere to a theoretical model, while the tunability of model parameters enables quantitative comparison with theory.
As an example, I will describe interacting spin-1/2 fermions confined to one-dimensional (1D). The low energy excitations are most likely collective in low dimensions, and thus realizes the Luttinger liquid. The low energy excitations are bosonic sound waves that correspond to either spin-density or charge-density waves that, remarkably, propagate at different speeds, thus realizing a spin-charge separation. This phenomena has been observed in electronic materials, but a quantitative analysis has proved challenging because of the complexity of the electronic structure and the unavoidable presence of impurities and defects. In collaboration with our theory colleagues, we made a direct theory/experiment comparison and found excellent agreement as a function of interaction strength [1]. We found that it was necessary to include nonlinear corrections to the spin-wave dispersion arising from back-scattering, thus going beyond the Luttinger model. More recently, we explored the disruption of spin correlations with increasing temperature [2], an effect that destroys spin-charge separation.
Our experiment uses Bragg spectroscopy to measure the momentum and energy resolved structure factor, S(q,ω), from which the two speeds of sound are determined.
1. R. Senaratne*, D. Cavazos-Cavazos* et al, “Spin-charge separation in a 1D Fermi gas with tunable interactions”, Science 376, 1305 (2022).
2. D. Cavazos-Cavazos, R. Senaratne, A. Kafle, and R.G. Hulet, “Realization of a spin-incoherent Luttinger liquid”, arXiv:2210.06306 (2022).
Bio:
Randall G. Hulet earned a BS degree at Stanford University and a Ph.D. in Physics at MIT. He was a National Research Council Fellow at the National Institute of Standards and Technology, where he worked on laser cooling of trapped atomic ions. He joined the faculty of Rice University in 1987 and he currently holds the Fayez Sarofim Chair in Natural Sciences. He has received many awards, including the I.I. Rabi Prize and the Davisson-Germer Prize of the American Physical Society, the National Science Foundation Presidential Young Investigators Award, a NASA Medal for Exceptional Scientific Achievement, and the Herbert Walther Award from the European Physical Society and the Optical Society of America. He is a member of the American Academy of Arts and Sciences.
Hulet is known for his many contributions to atomic physics including helping to develop methods for laser cooling and trapping of atoms. His group first realized Bose-Einstein condensation in an atomic gas with attractive interactions, created a degenerate Bose-Fermi mixture, and observed antiferromagnetic order in the Fermi-Hubbard model using ultracold atoms. More recently, his focus has been on interacting fermions and bosons confined to one-
dimension, which has produced detailed explorations of spin-charge separation and matter-wave solitons, respectively.
To view Dr. Hulet's website, please see here.
Event Location:
HENN 201
Event Time:
Thursday, February 9, 2023 | 10:00 am - 11:00 am
Event Location:
AMPL 311
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2023-02-09T10:00:00
2023-02-09T11:00:00
Aspects of Microsoft’s recent topological gap study
Event Information:
Abstract:
I will discuss the theory and data analysis techniques behind the recent study searching for Majorana zero modes. I will describe how the transport techniques can help identify the boundary and bulk signatures of the topological phase. The analytical insight is confirmed by extensive numerical study and data analysis. I will finish with an example of an experimental observation.
Event Location:
AMPL 311
Event Time:
Monday, February 6, 2023 | 3:00 pm - 4:00 pm
Event Location:
HENN 318
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2023-02-06T15:00:00
2023-02-06T16:00:00
Studying the neutron star equation of state with gravitational waves
Event Information:
Abstract:
Detections of neutron stars in binaries through gravitational waves offer a novel way to probe the properties of extremely dense matter. In this talk I will describe the properties of the signals we have observed, what they have already taught us, and what we expect to learn in the future. I will also discuss how information from gravitational waves can be combined and compared against other astrophysical and terrestrial probes of neutron star matter to unveil to the properties of the most dense material objects that we know of.
Bio:
Katerina Chatziioannou is Assistant Professor of Physics at the California Institute of Technology.
Katerina works on gravitational wave astrophysics and using data from ground-based and space-based gravitational wave detectors to study the properties of black holes and neutron stars. She is particularly interested in the properties of neutron stars and the states of matter in their extremely dense cores, as well as tests of the theory of gravity.
See here to view her research articles and here for a full list of publications.
Event Location:
HENN 318
Event Time:
Monday, February 6, 2023 | 11:00 am - 12:00 pm
Event Location:
Henn 318
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2023-02-06T11:00:00
2023-02-06T12:00:00
Noise Hunting for LIGO
Event Information:
TALK RECORDING AVAILABLE AT: https://drive.google.com/file/d/1PhFE8tQS_fp_SbSI3S0f2Gz8yTwXVsdp/view?usp=share_link
Abstract:
The Advanced LIGO interferometers operate very close to their noise floor. This means that, in contrast to off-the-shelf instruments, any variation in the noise will not only be easily detectable but also may have a negative impact on LIGO's ability to detect gravitational waves. In this seminar, I will discuss a number of examples of noise sources that have been detected over the years, how their cause was identified , and how (or if) the problem was eliminated. These examples will not be chosen necessarily for their importance but rather to illustrate a variety of noise sources and analysis approaches.
Event Location:
Henn 318
Event Time:
Thursday, February 2, 2023 | 4:00 pm - 5:00 pm
Event Location:
HENN 201
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2023-02-02T16:00:00
2023-02-02T17:00:00
Why is it so Difficult to Probe the Nature of Dark Matter?
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Abstract:
Ninety years after the first hints of its existence, the nature of dark matter remains elusive. The only physical property firmly supported by observations is the "Cold" aspect of dark matter. Decades of direct search experiments have helped to reduce the range of some parameters of the so-called Weakly Interacting Massive Particles (WIMPs) model, but no direct detection has yet been reported. In this context, the exploration of dark matter models, other than WIMPs, has gained momentum.
The WIMPs model is based on fundamental assumptions, assumptions which are generally not questioned although not supported by direct observations. Abandoning them opens the path to alternative models of dark matter, but in order to be credible, these models have to predict specific signatures. The coming era of large scale surveys (Euclid, Rubin, Roman, SKA, etc...), going to probe to unprecedented depth and resolution the entire electromagnetic spectrum, from radio to gamma-ray wavelengths, might be the best opportunity astronomers ever had to test the electromagnetic signature of dark matter.
In this talk, after reviewing the assumptions behind the WIMPs paradigm, I will introduce the Axion Quark Nugget model. No wild extension of the standard model of particle physics is needed, other than the existence of the QCD axion. The axion field triggers the formation of two types of nuggets, matter and antimatter, at the quark-hadron phase transition. These nuggets would constitute the dark matter we observe today. The interactions between baryonic matter and the antimatter nuggets lead to a variety of predictable electromagnetic signatures. There are hints that some of them might have already been seen, and some others are within reach of upcoming surveys.
Bio:
Doctoral Degree: University of Orsay, Paris XI, Astrophysics/Cosmology, 1997
Employment History
2014- Professor, Physics and Astronomy, UBC
2009-2014 Associate Professor, Physics and Astronomy, UBC
2004-2009 Assistant Professor, Physics and Astronomy, UBC
2002-2004 Chargé de Recherche CR1, CNRS, IAP, Paris, France (tenure)
2000-2002 Chargé de Recherche CR1, CNRS, IAP, Paris, France (tenure track)
1998-2000 Postdoctoral Fellow, CITA, Toronto, Canada
1997-1998 Postdoctoral Fellow, Max-Planck-Institut, Garching, Germany
Awards
2015 Friedrich Wilhelm Bessel Research Award from the Humboldt Foundation
2010 Peter Walls Institute for Advanced Studies Early Career Scholar award
2007-2012 Senior Fellow, Canadian Institute for Advanced Research Cosmology & Gravity program
1993-1996 PhD fellowship award from the french ministry of research and education
Event Location:
HENN 201