Young Suh Kim, 1935 - 2025

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Published: Monday, December 08 2025 05:19

Professor Emeritus Young Suh Kim died on October 25, 2025 at age 90.  Prof. Kim's research was dedicated to elucidating the connections between relativity, quantum mechanics, and the symmetries that underlie the laws of nature.

Born in Korea in 1935, Prof. Kim earned his Bachelor of Science degree from the Carnegie Institute of Technology (now Carnegie Mellon University) and his Ph.D. in Physics from Princeton University
in 1961. He stayed at Princeton to complete his postdoctoral research. At the invitation of Department Chair John S. Toll, Kim joined the University of Maryland faculty in 1962. At the time, he was the
youngest person to become assistant professor at the university. He retired in 2007.

While at Princeton as a graduate student, he studied Eugene Wigner’s influential 1939 paper on the inhomogeneous Lorentz group, and had the privilege of asking questions directly to Wigner. At the start of
Prof. Kim’s career at Maryland, Paul A. M. Dirac visited for one week, and Prof. Kim was assigned to serve as Dirac’s personal assistant. During this time, Dirac suggested to Kim that more physicists should study the relationship of Lorentz covariance to the internal symmetries of particles.

Prof. Kim’s early research centered on the representations of the Lorentz and Poincaré groups, the fundamental symmetries of special relativity. Together with Marilyn E. Noz, he developed the covariant harmonic oscillator model, providing a relativistically consistent description of the internal structure of bound systems. Their 1977 paper, “Covariant Harmonic Oscillators and the Parton Picture” (Physical Review D, 15, 335), offered an innovative framework linking the quark model of hadrons with Feynman’s parton picture of high-energy processes. This work sought to reconcile the static quark view with the dynamic, frame-dependent parton model through Lorentz-covariant formalism.

Professor Kim’s numerous papers appeared in leading journals including Physical Review, Physical

Review Letters, and Journal of Mathematical Physics. His 1989 paper, “Observable Gauge Transformations in the Parton Picture,” offered an important contribution to the study of relativistic symmetries in hadron structure by showing that the parton picture of fast-moving hadrons can be understood as a Lorentz covariant effect with the use of Wigner’s little group formalism, an insightful complement to the dynamical consequence of QCD interactions.  

He had a long collaboration with Wigner, co-authoring the 1990 paper “Space-time Geometry of  Relativistic Particles” in the Journal of Mathematical Physics. In it he uses Wigner’s little group formalism to unify the space-time geometry of relativistic particles — from massive quarks to massless photons — within a single Lorentz-covariant framework. Again complementing QCD, it is a deep symmetry-based reinterpretation of how internal quantum states (spin, helicity) are tied to external Lorentz transformations. His influential book “Theory and Applications of the Poincare Group” is a key resource for understanding how symmetries underpin modern physics, with discussions of how Poincaré symmetries explain conservation laws via Noether’s theorem. 

Prof. Kim is survived by his wife, son, daughter-in-law, two grandchildren, and a global community of former students, collaborators, and admirers. 

Y.S. Kim, Umirzak Makhmutovich Sultangazin, Richard Ferrell and Chuan S. Liu.

Y.S. Kim and Dieter Brill.

Y.S. Kim at a departmental holiday party. 

Gates Receives 2025 Barry Prize, Named Fellow of the American Mathematical Society and African Academy of Sciences

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Published: Thursday, December 04 2025 00:01

Distinguished University Professor Sylvester James Gates, Jr.  was recently named Fellow of both the American Mathematical Society and the African Academy of Sciences and received the 2025 Barry Prize for Distinguished Intellectual Achievement from the American Academy of Sciences & Letters. The Barry Prize honors “those whose work has made outstanding contributions to humanity’s knowledge, appreciation, and cultivation of the good, the true, and the beautiful.”

Original story: https://cmns.umd.edu/news-events/news/sylvester-james-gates-jr-barry-prize-fellow-ams-aas

Barkeshli Selected for Prestigious Simons Collaboration to Study Inner Workings of Artificial Intelligence

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Published: Wednesday, December 03 2025 01:34

As artificial intelligence (AI) rapidly transforms everything from medicine to scientific research to creative fields, a fundamental question remains unanswered: How do AI systems actually work?  

AI models help diagnose diseases, discover new drugs, write computer code and generate images, yet scientists still don't fully understand the principles underlying their remarkable capabilities. Solving this ‘black box’ problem—where we can see AI's outputs but can’t fully comprehend its internal workings—has become more urgent as these systems become more deeply embedded in society.

University of Maryland Physics Professor Maissam Barkeshli will help unravel that mystery. 

Barkeshli was one of 17 principal investigators recently chosen for the Simons Collaboration on the Physics of Learning and Neural Computation, an international research initiative that aims to investigate the complex inner workings of AI. The collaboration, which will receive $2 million annually for the next four years, brings together leading experts from physics, mathematics, computer science and neuroscience. The team will first identify key emerging phenomena in AI before isolating them and studying them systematically, forming smaller working groups to tackle specific questions, then combining their findings at the conclusion of the collaboration.

“Maissam exemplifies the intellectual agility we prize in our faculty,” said UMD Physics Chair and Professor Steven Rolston. “Originally hired for his work in condensed matter theory, he is pivoting to address the exciting and potentially impactful challenge of understanding why artificial intelligence models actually work, informed by the concepts of mathematical and statistical physics.”

At UMD, Barkeshli's primary research focuses on quantum many-body phenomena. He studies how collections of many particles like electrons in materials spontaneously organize into unusual or specific positions such as superconductors and quantum Hall systems. Such events are emergent phenomena, which occur when simple components interact to create behaviors that cannot be predicted from studying individual parts alone. 

“Fundamentally, the field is really about emergence,” Barkeshli noted. “It’s about understanding collective behavior that is qualitatively different when you go to different scales that you wouldn’t have seen at smaller scales.” 

For Barkeshli, intelligence and learning are forms of emergent phenomena as well. Just as billions of electrons can collectively create superconductivity, neural networks with billions of parameters somehow learn to reason and understand language. As he begins his collaboration with experts from multiple disciplines, Barkeshli believes the theoretical tools and perspectives that physicists have developed in understanding the natural world can help us understand how AI works as well.

“There are three core ingredients of AI systems that interact to produce intelligence: training data, neural network architecture and optimization algorithms that are used to train models,” Barkeshli explained. “There’s incredibly rich interaction between these ingredients, but they all act very differently between themselves and have their own peculiarities at the individual level. We don’t have a very good idea of how it all comes together or why it works so well.”

These interactions lead to even more mysteries. For example, Barkeshli noted that AI follows predictable “scaling laws.”

“As you increase the size of data, the network and the computing power spent on training, AI systems get better and better,” he said. “In some cases, they follow very predefined, almost law-like patterns, where they’re getting better in a very predictable way. This is an emergent phenomenon that isn’t understood very well that we hope to study.”

Current AI development relies heavily on trial and error, but Barkeshli’s work on emergent phenomena may be the key to answering fundamental questions—such as why the human brain can operate on about 20 watts of power, yet AI systems require much more energy to complete similar cognitive tasks. 

“People have been trying different ideas based on intuition, but a more systematic understanding of AI could unlock some useful capabilities, like bridging that efficiency gap between human brains and language models,” he explained. 

Although the Simons Collaboration will focus on the most fundamental aspects of AI systems, Barkeshli hopes that “peeking under the hood” will illuminate more profound applications for AI in everyday life. 

“There’s room for making immense improvements,” Barkeshli said. “With a deeper understanding of the fundamentals of AI, especially from a physicist’s point of view, we could come up with different kinds of curricula for data to train with, different kinds of architectures, different kinds of optimization algorithms—even entirely new paradigms that we haven’t thought of yet.”

Original story by Georgia Jiang: https://cmns.umd.edu/news-events/news/umd-physicist-selected-prestigious-simons-collaboration-study-inner-workings   

Chung Yun Chang, 1929 - 2025

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Published: Monday, November 03 2025 15:19

Professor Emeritus Chung Yun Chang died on October 29, 2025, in San Diego, California. He was 95.

Prof. Chang was a native of rural Hunan, China. He received a bachelor’s degree at National Taiwan University and a Ph.D. at Columbia University in 1965.  

Prof. Chang joined the University of Maryland Physics department in the mid-1960s and worked with George Snow and Bob Glasser on the analysis of bubble chamber data. In those days almost the entire 4^th floor of the Toll Physics Building consisted of bubble chamber scanning and measuring tables. Those were the days of establishing the properties of elementary particles that eventually led to the current Standard Model of Particle Physics. In the late 1960’s Prof. Chang and his coworkers worked on a K⁻p  Bubble Chamber exposure at Brookhaven National Lab to study decays and results that were inconsistent with an |ΔI| = ½ rule. The analysis of this exposure continued for a long time and the film existed at Maryland until the 1990’s when it was finally mined for its silver content.

With the advent of Fermilab, Prof. Chang and the Maryland group worked on a number of bubble chamber experiments at Fermilab. Fermilab experiment E2B was a hybrid spectrometer experiment with optical spark chambers measuring forward tracks produced by 100 Gev π− interactions in the Argonne 30” hydrogen bubble chamber. The spark chambers and the bubble chamber were triggered if two or more forward tracks were detected by dE/dx deposits in 3 independent scintillation counters, indicating the presence of a high multiplicity event. A hybrid triggered system avoided taking photos of uninteresting events. Profs. Chang, Snow and Glasser were joined by Phil Steinberg on this experiment.

Prof. Chang also worked with Prof. Steinberg on a Magnetized Beam Dump experiment at Fermilab looking for neutral heavy leptons at this time.

George Snow conceived of a search for Charm in the 15 foot Fermilab Bubble Chamber filled with deuterium before the discovery of the J/Ψ. Although the proposal was accepted it was delayed for many years. Prof. Chang and his coworkers did find several charm candidate events when the Bubble Chamber finally took data, but by then Charm was no longer just a conjecture. The Standard Model was on its way to being finalized.

After the discovery of the ϒ at Fermilab, and the proposal of QCD as the underpinning of the strong interactions, the Standard Model was heading towards completion. A set of experiments at DESY in Hamburg, Germany established the existence of the gluon, the particle that binds the quarks in strong interactions. Prof. Chang worked with Gus and Bice Zorn, Andris Skuja and Prof. Glasser on the PLUTO experiment at PETRA. PETRA was an e⁺e^- collider. In 1979, three experiments at PETRA observed 3-particle jet events that were consistent with gluon production. Later the four experiments that operated at PETA were awarded a special EPS prize for the discovery and characterization of the gluon in strong interactions. PLUTO made many early contributions to our understanding of QCD and particle jet fragmentation as well as introducing the study of γγ production of hadrons.

After PLUTO on PETRA, Prof. Chang worked on the OPAL experiment at LEP (the Large Electron Positron collider) at CERN, Geneva, Switzerland.  While waiting for OPAL to begin data taking, Prof. Chang worked with Prof. Steinberg to find evidence for muonium and antimuonium oscillations. They did not find such evidence but for a while they had the best limits for non-existence of the phenomenon.

At LEP, Prof. Chang worked with Prof. Snow on the Z line-shape. The Maryland group had a major role in the OPAL experiment, leading the construction of the hadron calorimeter among other contributions. The analysis of the data from OPAL and other three experiments at the Z pole and later at higher energies led to the most precise measurements of the Electroweak interactions, validating the Standard Model predictions. Working with his students, Prof. Chang carried out studies of Z line-shape and its decay properties, and searches for new particles beyond the Standard Model.

After his retirement in 1997, Prof. Chang continued to do research, and had a deep interest in neutrino mixing studies. He was a Fellow of the American Physical Society.

Further information is posted here: https://www.dignitymemorial.com/funeral-homes/california/san-diego/pacific-beach-la-jolla-chapel/9560

Y.S. Kim, Umirzak Makhmutovich Sultangazin, Richard Ferrell and Chuan S. Liu.

Y.S. Kim and Dieter Brill.

Y.S. Kim at a departmental holiday party. 

Jaron E. Shrock Cited for Outstanding Thesis

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Published: Monday, September 29 2025 09:33

Jaron E. Shrock has been named the 2025 recipient of the American Physical Society’s Marshall N. Rosenbluth Outstanding Doctoral Thesis Award. Shrock was cited for the first demonstration of multi-GeV laser wakefield acceleration using a plasma waveguide in an all-optical scheme.

After graduating from Swarthmore College in 2018, Jaron joined Distinguished University Professor Howard Milchberg’s Intense Laser Matter Interactions lab, where The accelerator in action. his research has focused on using lasers to accelerate electrons to multi-GeV energies over meter-scale distances. The laser intensities needed to do this are extremely high, and the key element that keeps them high is a plasma waveguide—first realized by Dr. Milchberg at the University of Maryland in the 1990’s. The plasma waveguide is analogous to a glass fiber optic cable, but it can confine laser intensities more than 7 orders of magnitude higher than would destroy the glass fiber. “Shrinking  a km-long machine to fit inside a university lab, manufacturing facility, or hospital has enormous potential to bring advanced light and radiation sources to a variety of applications, and provides a possible path towards developing compact high energy colliders for probing fundamental physics”, said Shrock.

Dr. Shrock defended his thesis, Multi-GeV Laser Wakefield Acceleration in Optically Generated Plasma Waveguides, in 2023, and has also been recognized with the John Dawson Thesis Prize at the 2025 Laser Plasma Accelerators Workshop in Ischia, Italy. The success of the Maryland platform for laser acceleration has led to its installation for collaborative experiments at leading high power laser facilities in the US and Europe. Jaron is continuing his work at UMD as a postdoc, both helping to install the UMD platform at the other facilities and doing experiments on UMd’s new 100 terawatt laser system.  In thinking about the future of this research, Jaron says “It’s been thrilling (and exhausting!) to see this platform grow from ideas developed by our small team to the centerpiece of international research efforts, and I believe we’re only scratching the surface of what these accelerators can do.”

Shrock (right) with Ela Rockafellow (left) installing a prototype 1 meter gas jet on the ALEPH laser system at Colorado State University.Jaron is the fourth of Milchberg’s students to win the award, joining Thomas Clark (1999), Ki-Yong Kim (2004) and Yu-Hsin Chen (2012).

“Congratulations to Jaron for this outstanding achievement,” said physics chair Steve Rolston. “And kudos to Howard Milchberg for establishing such a constructive and creative atmosphere.”

The award consists of $2,000, a certificate, and an invitation to speak at the November 2025  Meeting of the APS Division of Plasma Physics (DPP) in Long Beach, California.