Spring 2023 Schedule
Feb 21, 2023
Yao-Yuan Mao University of Utah
Host:
Kai-Feng Chen
Time: 2:20 pm
- 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Illuminating the dark universe with galaxies
Abstract
Dark matter and dark energy remain the mysterious components in the current standard model of cosmology, and many current and upcoming experiments and astronomical surveys are poised to bring exciting discoveries about the physical nature of these dark components. Since the dark components are not directly observable, the interpretation of the results from cosmological surveys and dark matter searches often relies on, and sometimes is limited by, our understanding of the relation between visible galaxies and dark cosmic structures (dark matter halos). In this talk, I will discuss the recent progress in modeling some important features of the so-called galaxy-halo connection, including the low-mass end behavior of the said connection (at dwarf galaxy scale), the role the halo-subhalo interaction plays, and the degree at which the galaxy assembly depends on halo assembly (commonly known as assembly bias). I will demonstrate how cosmological simulations and new observations have advanced the galaxy-halo connection models, and how these improved models can in turn further our understanding of dark matter and dark energy.
Brief Bio
Dr. Yao-Yuan Mao (they/he) is an Assistant Professor of Physics and Astronomy at the University of Utah. Yao-Yuan received B.S. in Physics from NTU in 2009, and Ph.D. in Physics from Stanford University in 2016. Yao-Yuan then conducted postdoctoral research at the University of Pittsburgh as a PITT PACC Langley Fellow, and later at Rutgers University as a NASA Einstein Fellow. Yao-Yuan uses astronomical surveys and numerical simulations to study astrophysics, with a focus on dwarf galaxies and dark matter. Yao-Yuan is currently co-piloting the SAGA Survey, an ongoing spectroscopic galaxy survey aiming to characterize Satellites Around Galactic Analogs, and is also an active member of the Rubin Observatory LSST Dark Energy Science Collaboration. For more information about Yao-Yuan, see https://yymao.github.io/.
Mar 07, 2023
Lisa Kewley Harvard University
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Next Generation Modeling of HII Regions and Emission-line Galaxies
Abstract
I will present our our new state-of-the-art Messenger Monte Carlo MAPPINGS V code (M ³ ). The turbulent ISM causes inhomogeneity of electron temperature and density within the nebula, which is most effectively modeled through Monte Carlo ray tracing methods. We analyze the dependence of different optical emission lines on the complexity of nebular geometry, finding that the emission lines residing on the nebular boundary are highly sensitive to the complexity of nebular geometry, while the emission lines produced throughout the nebula are sensitive to the density distribution of the ISM within the nebula. Our fractal photoionizationmodel demonstrates that a complex nebular geometry is required for the accurate modeling of H II regions and emission-line galaxies. Finally, I will discuss the opportunities for these types of models for understanding galaxy formation and evolution with the current and next generation telescopes including JWST and the GMT.
Brief Bio
Lisa Kewley is Director of the Center for Astrophysics | Harvard & Smithsonian. She is Director of the Smithsonian Astrophysical Observatory, Director of the Harvard College Observatory, and Professor of astrophysics at the Harvard Department of Astronomy. Kewley obtained her PhD in 2002 from the Australian National University on the connection between star-formation and supermassive black holes in galaxies. She was a Harvard-Smithsonian Center for Astrophysics Fellow and a NASA Hubble Fellow. Her awards include the 2006 American Astronomical Society Annie Jump Cannon Award, the 2008 American Astronomical Society Newton Lacy Pierce Prize, and the 2020 US National Academy of Science James Craig Watson Medal. In 2014, Kewley was elected Fellow of the Australian Academy of Science “for her fundamental advances in understanding of the history of the universe, particularly star and galaxy formation”, and in 2015, Kewley was awarded an ARC Laureate Fellowship, Australia’s top fellowship to support excellence in research. In 2020, Kewley was awarded the US National Academy of Sciences James Craig Watson Medal, in 2021 she was elected to the US National Academy of Sciences, and in 2022 she was elected to the American Academy of Arts and Sciences. From 2017-2022, Kewley implemented her scientific vision through her Australian Research Council Centre of Excellence in All-Sky Astrophysics in 3D (ASTRO 3D). In July 2022, Kewley became Director of the Center for Astrophysics | Harvard & Smithsonian. At the CfA, she is implementing an ambitious new vision for the next generation space and ground-based telescopes, petabyte-scale data handling, new diversity and inclusion initiatives, and nation-wide education and outreach programs.
Mar 13, 2023
Dam Thanh Son University of Chicago
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
UnNuclear Physics: Conformal Symmetry in Nuclear Reactions
Abstract
Conformal symmetry plays an important role in quantum field theory and statistical physics. A nonrelativistic version of the conformal symmetry, also called Schrödinger symmetry, is approximately realized in various physical systems, including neutrons in nuclear physics and ultracold atoms. After going through some basic facts about nonrelativistic conformal field theory, we describe one concrete application of such a theory in the physics of nuclear reactions with several neutrons in the final state.
Brief Bio
Dam Thanh Son was born in Hanoi, Vietnam. He studied at Moscow State University and received his PhD in Physics from the Institute of Nuclear Research of the Russian Academy of Sciences. He is currently a Professor at the University of Chicago. His research interest includes quantum field theory, particle physics, nuclear physics and condensed matter physics.
Mar 14, 2023
Yasushi Suto University of Tokyo, Head of RESCEU and UTAP
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Spin-orbit architectures of transiting planetary systems: Rossiter-McLaughlin effect and asteroseismology
Abstract
A significant fraction of exoplanetary systems is known to exhibit spin-orbit misalignments. This surprising fact has been mainly revealed by a spectroscopic method, known as the Rossiter-McLaughlin effect for transiting planetary systems. This method measures the projected angle between the stellar spin and the planetary orbital axes, but is insensitive to the obliquity of the stellar spin with respect to the observer. Asteroseismology offers a unique method to infer the stellar obliquity in a complementary fashion. In this talk, I will first review the current statistics of the observed spin-orbit angles and proposed models for the origin of the misalignment. Then I will show our recent work on the spin-orbit architecture of transiting planetary systems using asteroseismology, and discuss its implications.
Brief Bio
Yasushi Suto is a professor in the Department of Physics and the director of Research Center for the Early Universe (RESCEU), the University of Tokyo. He earned his Ph.D. in physics from the University of Tokyo in 1986. After spending a couple of years as a Miller Research Fellow at the University of California, Berkeley, he joined faculty at Ibaraki University, Research Institute of Theoretical Physics, Hiroshima University, and the Yukawa Institute of Theoretical Physics, Kyoto University, before returning to the University of Tokyo in 1993. His research interests include observational cosmology and exoplanets. He received the Hayashi Chushiro Prize in 2004 from the Astronomical Society of Japan, and served as a Member of the Science Council of Japan during 2011 and 2017.
Mar 21, 2023
Hong-Yu Chu National chung cheng University
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Ferrofluid drop in DC/AC magnetic field
Abstract
We report that the responses of the ferrofluid drop in the time-constant and time-varying magnetic field. Ferrofluid material not only exhibits the fluid property like surface tension and element transport but also can be manipulated by the magnetic field. A model is proposed that regards the bulk magnetization of the ferrofluid drop in the magnetic field as a magnetic dipole. The magnetic length coefficient denoting the ratio of the magnetic length of the dipole and the length of the major axis of the deformed drop is found scaling relation and is consistent with experimental results. The prolate-shaped traveling ferrofluid drops are demonstrated to measure the gradient of the magnetic field in space. We also report the stretch–shrink–rotation motion of a ferrofluid drop in a time-varying magnetic field along the x direction. The drop performs stretch and shrink motion at low magnetic field due to the balance of magnetic force and surface tension as observed in many investigations, but it exhibits rotating motion at high magnetic field. We find that the size of elongated drop shows transitions at Rayleigh frequency of drop and at the frequency with maximum growth rate. The phase diagram of growth rate to the frequency and the strength of applied magnetic field reveals the threshold for drop to rotate. It is suspected that the induced transverse magnetization for the magnetic torque is associated with the phase lag between the time-varying magnetic field and the deformation of drop which leads to the rotation of drop.
Brief Bio
Prof. Hong-Yu Chu received his Ph.D. degree in physics at National Central University in 2006. He then joined the Department of Physics in National Chung Cheng University as an assistant professor in 2007 and was promoted to the full professor in 2016. His research focuses on the RF dusty plasma, various kinds of atmospheric pressure plasmas, plasma-liquid-gas interaction, motions of bouncing drops on liquid surface, shear flow in gas and liquid, and manipulation of ferrofluid drops.
Mar 28, 2023
Pin Chieh Wu National Cheng Kung University
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Next-generation of Optical System –Nanophotonic Metasurface for Light Management and Applications
Abstract
Metasurfaces, artificially designed nano-scatterers, have attracted immense attention because of their remarkable ability to control the optical properties and wavefront at a subwavelength scale. Thus, they hold promise for various flat optical applications such as compact spectrometers and low-profile spatial light modulators. In this talk, I will first discuss the intriguing characteristics of optical metasurfaces for phase modulation, amplitude control, and dispersion engineering, which enable feasible applications of focusing metalens and achromatic metasurface devices. Subsequently, the presentation will shift to several approaches, such as automatic inverse design, toroidal resonance modes, and plasmonic Huygens source utilized to accomplish high-performance metasurfaces. Lastly, a metasurface-integrated microlaser that modulates the light properties at the source will be discussed.
Brief Bio
Pin Chieh Wu is an Associate Professor in the Department of Photonics at National Cheng Kung University (NCKU). Dr. Wu completed his Ph.D. in Applied Physics at National Taiwan University (NTU). Afterward, he joined Nanyang Technological University, Singapore, as a Postdoctoral Research Fellow. Before he joined NCKU, he worked as a Postdoctoral Fellow at the California Institute of Technology (Caltech). Dr. Wu’s group has primarily focused on nano-optics and nano-photonics, from fundamental physical analysis to practical applications, especially for plasmonics, metamaterials, and metasurfaces for light manipulation and low-profile nanophotonic components.
Apr 11, 2023
Yun-Tse Tsai SLAC National Accelerator Laboratory
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
“Near Detector” for Supernova Neutrino Measurements in DUNE
Abstract
Neutrinos are the electrically neutral elementary particles with finite mass. The discovery of their non-zero masses is the first instance of a conflict with the Standard Model of particle physics, which has successfully described elementary particles and interactions but leaves questions unanswered. The fruitful results from neutrino experiments in the past two decades provide us with a paradigm, but further precision measurements are required to address the fundamental questions.
The Deep Underground Neutrino Experiment (DUNE), the flagship particle physics experiment in the US, aims to answer important questions in neutrino physics, and to detect neutrinos from explosions of core-collapse supernovae. In this talk, I will be focused on the detector technology used in DUNE, liquid-argon time-projection chambers (LArTPCs), and the development of supernova neutrino measurements in DUNE.
Brief Bio
Yun-Tse Tsai is an associate scientist at SLAC National Accelerator Laboratory. Her research interests have been focused on neutrino experiments based on liquid-argon time-projection chambers (LArTPCs), including MicroBooNE, ICARUS in the Short Baseline Neutrino Program (SBN) at Fermilab, DUNE, and potential of future LArTPC detectors in the COHERENT experiment. She has led the delivery of the MicroBooNE data acquisition system, the astroparticle and exotic physics group of MicroBooNE, the TPC reconstruction working group of SBN, the high energy physics group of DUNE, and the project of the first LArTPC prototype detector at SLAC.
Apr 18, 2023
Tai-Wei Wu Director, Institute of Chemistry at Academia Sinica
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
The Molecular Tango of Gas Hydrates: How Methane and Water Form an Intimate Structure with Lessons for Nucleation and Energy
Abstract
Methane gas, being a hydrophobic hydrocarbon, has low solubility in water. Yet at moderately high pressures and low temperatures, such as those occurring at the ocean floor or in oil and gas pipelines, these two species crystallize together into a molecular lattice of hydrogen bonded water molecules with polyhedral cages containing individual methane molecules. Given the ubiquity of these two compounds, these methane “clathrate hydrates” are found in enormous quantities on earth and form easily in pipelines, and thus have significant energy and environmental implications. In addition to being a generic behavior of water and hydrophobic molecules, gas hydrates have been of scientific interest as a model system for multicomponent multiphase nucleation. However, the nucleation of methane hydrates has been difficult to study, since it is a rare stochastic event that occurs in nanoseconds at a random location on a nanometer length scale. By analyzing ensembles of large-scale microseconds molecular dynamics simulations, we captured the mechanism of spontaneous hydrate nucleation, revealing an intricate cooperative dance between methane and water molecules. These observations and resulting insights overturned leading hypotheses for methane hydrate formation, and have recently led to the discovery of surprising new order-transmission mechanisms for heterogeneous nucleation in general.
Brief Bio
David Wu is Director and Research Fellow of the Institute of Chemistry at Academia Sinica. He is a Joint Professor of Chemical Engineering at National Taiwan University, and also a Professor (on leave) in Chemistry and in Chemical and Biological Engineering at the Colorado School of Mines. He earned his A.B. in Chemistry from Harvard University in 1985 and his Ph.D. in Chemical Physics from the University of California at Berkeley in 1991, working on the quantum statistical mechanics of the solvated electron. He was then a Junior Research Fellow in the Condensed Matter Theory group at the Cavendish Laboratory in Cambridge University followed by a postdoc in the Chemical Engineering department at the University of California at Santa Barbara, where he worked on polymer and colloid hydrodynamics and statistical physics. In 1996, he joined the faculty at the Colorado School of Mines, where from 2009-2014 he was the Associate Director for the Center of Hydrate Research, and from 2012-2017 he was Head of the Chemistry and Geochemistry department. In 2003 he spent a year as the Visiting Joliot Chair Professor at ESPCI, Paris. He was a visiting researcher/professor at National Taiwan University in 1996 at the Center for Condensed Matter Sciences, and in the Chemical Engineering department in 2010 and in 2017. He returned to Taiwan in 2021 to assume the Directorship of the Institute of Chemistry, and also received the CTCI Foundation Science and Technology Recruitment Fellowship. His research interests include theory and modeling of soft materials, statistical mechanics and simulation of molecular systems, and gas hydrate science and applications.
Apr 25, 2023
Sara Ellison University of Victoria
Host:
Kai-Feng Chen
Time: 2:20 pm - 3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
Clash of the Titans: Star formation, AGN and quenching in galaxy mergers
Abstract
Astronomy's current model of galaxy evolution is built on a foundation of hierarchical growth, in which small galaxies merge together to form larger ones. In addition to the simple accrual of mass, this merging process is predicted to fundamentally change the galaxies' properties, such as dramatic morphological transformations, the triggering of bursts of star formation and high rates of accretion onto the central supermassive black hole. In this talk I will explain the physical processes behind these predictions, and present the observations that we are performing in order to test the theory. Although many of the predictions are indeed borne out by experiment, there have been some surprising conflicts as well, that demand revisions to our models of how mergers shape galaxy evolution.
Brief Bio
Sara Ellison received her PhD in 2000 from the University of Cambridge. After a postdoctoral fellowship at the European Southern Observatory in Chile, she moved to the University of Victoria in 2003 to take up a Canada Research Chair where she has been a full professor since 2014. Sara has received numerous research honours and awards including the Annie Jump Cannon Award from the American Astronomical Society, the Peter Martin Award from the Canadian Astronomical Society (CASCA) and the Rutherford medal in physics from the Royal Astronomical Society of Canada. She has also served in a number of prominent community roles, including as President of CASCA. In 2015 she was elected to the Royal Socity of Canada's College of new scholars. A strong believer in work-life balance, Sara is a keen sportswoman (particularly active in triathlons), traveller (with a current tally of 64 countries) and has written a best-selling guide book about snorkelling around Vancouver Island.
