Spring 2025 Schedule
Feb. 18, 2025
Daniel Wang
UMass Amherst
[Canceled] Exploring the Galactic Core: The mysteries of Sagittarius A* - our supermassive black hole
Host: Ting-Wen Lan
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Abstract
The presence of supermassive black holes (SMBHs) in galaxies is well known. But why most of them remain silent in today's Universe is poorly understood. Sgr A* at the center of our Milky Way Galaxy is an asymptotic example of such a low-luminosity SMBH. The proximity of Sgr A* provides a unique opportunity to observe and understand the dynamics of black hole activity and its interplay with its Galactic nuclear environment. Based primarily on deep X-ray observations and computer simulations, I will discuss what Sgr A* has been doing recently and how this interplay may have determined the life cycle of black hole activity and other galactic nuclear processes that profoundly affect the structure and evolution of our Galaxy. Such studies, complemented by observations of other nearby SMBHs and their environments, provide insights into the functioning of galactic ecosystems and astrophysical processes under extreme conditions.
Brief Bio
Daniel Wang is a professor in the Astronomy Department at University of Massachusetts Amherst. He received his Ph.D. in astronomy in 1990 from Columbia University and was awarded the 1992 ASP Robert J. Trumpler Award for Outstanding North American Ph.D Dissertation Research in Astronomy. He was then a NASA Edwin P. Hubble Postdoctoral Fellow at the University of Colorado and later a Lindheimer Fellow at Northwestern University. He was also a member of the Institute for Advanced Study at Princeton and a Raymond and Beverley Sackler Distinguished Visiting Astronomer at the University of Cambridge. He was honored first as the Siyuan Visiting Professor and later as the Yixing Visiting Chair Professor in the School of Astronomy and Space Science at Nanjing University, later as a US Fulbright Scholar and a visiting professor at Pontificia Universidad Catolica de Chile, and as a visiting professor at Tsung-Dao Lee Institute and Shanghai Jiao Tong University. He is currently a visiting scientist at ASIAA. His research is primarily on high-energy astrophysics, covering a broad range of topics: compact objects, stellar feedback, and the hot circumgalactic/intergalactic media, as well as galactic nuclei and their environments.
Feb. 25, 2025
J. Xavier Prochaska
UC Santa Cruz
Three Decades of Science in Silhouette
Host: Ting-Wen Lan
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Abstract
I will discuss a perspective on counting and locating the majority of our Universe's baryons from the scant signatures imprinted on the light and signals of distant sources (quasars and fast radio bursts). These data offer what I consider the most robust measurement of a cosmological parameter (the baryonic mass density) and I'll describe previous and ongoing efforts to establish where the majority of this matter resides. If time permits, I'll briefly detail my new adventure to measure – again in silhouette – the constituents of our Earth's oceans (e.g. phytoplankton).
Brief Bio
J. Xavier Prochaska is a distinguished professor at the University of California Santa Cruz. He is also an associated member of the Kavli IPMU at the University of Tokyo and the National Observatory of Japan. He received his PhD from UC San Diego in 1998 and after that he joined the Carnegie Observatories as a Carnegie and Hubble fellow. In 2002, he became a faculty member at UCSC. He has been working on probing the distribution of baryons in various forms, diffuse gas, molecules in and out of galaxies across cosmic time by utilizing both the collecting power of large telescopes, including the Hubble Space Telescope, the Keck telescope in optical, and ALMA in radio, as well as the statistical power provided by large sky surveys, including the SDSS and DESI. He is one of the pioneers in applying machine learning (ML) techniques to astronomical datasets. Several years ago, he established a team to study the nature of fast radio bursts and search for their host galaxies. With such information, along with his collaborators, Prof. Prochaska resolved the so-called missing baryon problem. In addition to astrophysics, he has been working on physical oceanography and is currently an affiliate faculty member of the Ocean Sciences Department at UCSC. In 2023, he received the Simons Pivot Fellowship to support his exploration in oceanography.
Mar. 04, 2025
Sinya Aoki
YITP, Kyoto
Conservation laws and gravity
Host: Jiunn-Wei Chen
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Abstract
In this colloquium, I discuss conservation laws in a presence of gravity including general relativity. After an introduction, contents of my colloquium are
I. Energy non-conservation in general relativity
I-1. Why is energy conserved?
I-2. Energy non-conservation in general relativity: Expanding Universe
I-3. Cases for energy conservation in a curved spacetime
II. Gravitational fields carry energy? Noether’s 2nd theorem and general relativity
II-1. Energy of gravitational field?
II-2. Noether’s 2nd theorem
II-3. Noether’s 2nd theorem in general relativity
III. Conserved charge in curved spacetime (including GR)
III-1. Proposal for a conserved charge
III-2. Perfect fluid and Stefan-Boltzmann law
III-3. A simple model of expanding Universe (scalar+radiation)
IV. Summary
Questions and comments during my presentation are very welcome.
Brief Bio
Professor Sinya Aoki is the director of the Yukawa Institute for Theoretical Physics at Kyoto University. He received his PhD in 1987 from the University of Tokyo. After postdoctoral terms at Brookhaven National Laboratory and the State University of New York, Stony Brook, in the USA, he joined the faculty of the University of Tsukuba in 1991. He then moved to the Yukawa Institute for Theoretical Physics at Kyoto University in 2013 and later served as the Director of the Institute.
Professor Aoki is an expert in theoretical high-energy physics, especially in Lattice Quantum Chromodynamics (LQCD). A new phase structure he discovered as a graduate student is now commonly referred to as "Aoki fingers." His research on Nuclear Force from Lattice QCD with Hatsuda and Ishii was awarded the prestigious Nishina Memorial Prize in 2012 and the MEXT Commendation for Science and Technology in 2014.
Mar. 11, 2025
Jiadong Zang
University of New Hampshire
An artificial intelligence era of magnetism
Host: Danru Qu / Shao-Yu Chen
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Abstract
Magnetic materials play a crucial role in numerous aspects of daily life, yet their choice remains limited, and discovering new ones is highly challenging. In recent years, the emergence of machine learning and artificial intelligence has revolutionized materials discovery, offering new hope for identifying novel functional magnetic materials. However, a comprehensive database of magnetic materials is still lacking. In this talk, we address this challenge by leveraging advanced large language models to extract material properties from experimental data reported in peer-reviewed journal articles. The database currently includes more than 30,000 magnetic materials and still keeps growing. Our database is highly inclusive and also encompasses superconductors and thermoelectric materials. We hope this resource accelerates materials discovery and paves the way for a new era in magnetism. No background on magnetism and condensed matter is required for this talk.
Brief Bio
Prof. Jiadong Zang received bachelor’s degree in 2007 and PhD degree in 2012, both from Fudan University. He was a postdoctoral fellow in the Institute of Quantum Matter at the Johns Hopkins University during 2012-2015. In 2015, he joined the Department of Physics at the University of New Hampshire (UNH) as an assistant professor. He was promoted to associate professor in 2020, and then to the full professor in 2023. His research field is theoretical condensed matter physics with a focus on many aspects of magnetism, including topological magnetism, quantum transport, and functional magnetic materials. Prof. Zang was recipient of IUPAP Young Scientist Prize in the field of magnetism and the Alexander von Humboldt Fellowship for Experienced Researchers. He is currently the chair of the APS New England Section.
Mar. 18, 2025
C.-J. David Lin
National Yang Ming Chiao Tung University
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Mar. 25, 2025
Wei-Li Lee
AS Institute of Physics
Host: Cheng-Tien Chiang
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Apr. 01, 2025
Wolfgang Kuch
Freie Universität Berlin
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Apr. 08, 2025
Midterm exam
Apr. 15, 2025
Ting-Wan Chen
National Central University
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Apr. 22, 2025
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Apr. 29, 2025
Yuan-Ron Ma
National Dong Hwa University
Host: Cheng-Tien Chiang
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
May 06, 2025
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
May 13, 2025
Wen-Bin Jian
National Yang Ming Chiao Tung University
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
May 20, 2025
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
May 27, 2025
Sut-Ieng Tam
National Yang Ming Chiao Tung University
Host:
Time: 2:20 pm
Place: Room 104, CCMS-New Phys. building
Joint Colloquia