Research, teaching and outreach in Physics at UW–Madison
Month: August 2023
Through machine learning maps, cosmic history comes into focus
By Jason Daley, UW–Madison College of Engineering
For millennia, humans have used optical telescopes, radio telescopes and space telescopes to get a better view of the heavens.
Today, however, one of the most powerful tools for understanding the cosmos is the computer chip: Cosmologists rely on processing power to analyze astronomical data and create detailed simulations of cosmic evolution, galaxy formation and other far-out phenomena. These powerful simulations are starting to answer fundamental questions of how the universe began, what it is made of and where it’s likely headed.
“It is extremely expensive to run these simulations and basically takes forever,” says Kangwook Lee, an assistant professor of electrical and computer engineering at the University of Wisconsin-Madison. “So they cannot run them for large-scale simulations or for high-resolution at that same time. There are a lot of issues coming from that.”
Instead, machine learning expert Lee and physics colleagues Moritz Münchmeyer and Gary Shiu are using emerging artificial intelligence techniques to speed up the process and get a clearer view of the cosmos.
Choy leads team awarded National Science Foundation Quantum Sensing Challenge Grant
The National Science Foundation has selected a proposal “Compact and robust quantum atomic sensors for timekeeping and inertial sensing” by an interdisciplinary team led by University of Wisconsin-Madison researchers for...
Ke Fang, Ellen Zweibel earn Simons Foundation funding to study electrodynamics in extreme environments
Much of what we understand about fundamental physics is based on experiments done in the convenient “lab” of earth. But our planet is just one location, with its own relatively mild electromagnetic field. Do forces and energies work the same on earth as they do in all corners of the universe?
“It’s never guaranteed, as we see many theories break down at extreme environments,” says University of Wisconsin–Madison physics professor Ke Fang. “For example, a neutron star offers a magnetic field that is trillions of times stronger than on the Earth, and magnetars offer a field that is hundreds of trillions of time stronger. They are natural places to test many fundamental physics theories.”
SCEECS has six main research questions, three centered on understanding electrodynamics in neutron stars and three centered in black holes. Each question pairs at least one senior-level investigator with an early-career co-investigator. Zweibel serves as the lead investigator on her black hole question, and she is paired with Richard Anantua at UT-San Antonio. Fang is co-investigator on a neutron star question, and she is paired with Anatoly Spitkovsky at Princeton.
The neutron star “labs” that Fang is using are amongst the most dense stars in the universe — as small as 10 kilometers in diameter and with densities a million billion times that of water. High energy particles streaming from neutron stars are detectable on Earth, but they tend to be significantly altered by the time they make it here.
“How do those particles survive, in the sense that these extreme energy particles would interact with the surrounding media and produce secondary particles, and how do these interactions play a role in converting what you see on Earth?” Fang’s research asks. “There are also several major questions revealed by recent observations, such as extended TeV gamma-ray halos around neutron stars that are completely new phenomena. We would like to go from first principle physics to understand these phenomena.”
Zweibel’s research will use the extreme environment of spinning black holes, where the electromagnetic field has recently been identified as a major factor in accretion flows, or the movement of gases into the dense center. Her question asks how these accretion flows contribute to magnetizing black holes to form relativistic jets, or powerful emissions of radiation and high-energy particles.
“Accretion disks, their magnetic fields, and their magnetized jets are found throughout the Universe. They play essential roles in star formation, in the evolution of double, or binary stars, and in many other astrophysical settings,” Zweibel says. “The magnetized accretion disks surrounding black holes are by far the most extreme, and test our theories to the limits. Remarkably, we can circle back to laboratory plasma experiments, including some right here at UW, to study magnetized disks and jets as well.”
SCEECS is housed at Stanford University and includes researchers from 14 other US and international universities. UW–Madison and Columbia University are the only universities that have more than one investigator in the collaboration. Most of the funding will be used to support investigators, postdoctoral fellows, and graduate students.
The collaboration plans to host an in-person kick-off in October at Stanford with regular virtual meetings throughout the year. Those meetings will be a place where everyone involved in the research, including students, postdocs, and faculty, can provide updates and seek feedback. Larger-scale collaborations such as this one are nothing new to physicists, but those groups are almost always made up of experimental physicists.
“It’s rare for theorists to be in a larger collaboration because we’re usually working alone or in a small group,” Fang says. “This program is exciting because it collects leading theorists in the field from many different institutions and provides a network for us to collaborate with each other.”
The Simons Foundation’s mission is to advance the frontiers of research in mathematics and the basic sciences. The Foundation makes grants in four areas, including Mathematics and Physical Sciences, through which this collaboration is supported.
Zain Abhari selected for SACLA graduate internship
Congrats to Physics PhD student Zain Abhari for being selected to the SACLA Research Support Program for Graduate Students. The one-year internship run by SACLA (the SPring-8 Angstrom Compact free electron LAser) accepts graduate students with a demonstrated interest in using X-ray free electron lasers (XFELs) for their research and provides them with training and beam time at the facility in Japan.
Prior to her acceptance in the program, Abhari had already spent time at SACLA as part of her research in Uwe Bergmann’s group. While there, her collaborator told her about the program and recommended she apply.
“My goal after the PhD is to work at one of these large-scale facilities, specifically the X-ray free electron lasers and there’s only six of them right now in the world,” Abhari says. “If I can get my foot in the door in Japan, or get the experience to then help me with any of the other ones, that would be pretty awesome.”
Abhari was also interested in the program because SACLA’s laser aligns well with the goals of her thesis research, which is to obtain intense, stable XFEL pulses to apply to different spectroscopy techniques. For about the past decade, XFEL has allowed researchers to make ultrafast movies of molecular changes, essentially helping them to see chemical reactions take place. But x-ray lasers are “dirty,” and they contain multiple wavelengths of light of varying intensity. Last year, Bergmann and his colleagues somewhat accidentally discovered a way to make the pulses cleaner through two intense, femtosecond-spaced pulses.
Even though the researchers think they know how the useful pulses work, producing and controlling them are a completely different story — and one that Abhari hopes to unravel in her research.
“Right now, they’re just random,” Abhari says. “So the goal is to understand them. And then if we understand them, can we control them? If we can control them, can we apply them?”
Abhari will travel to Japan for three months beginning in September, where the program provides on-campus housing and time on the laser. Without the access she is now granted by this internship, her research would have been much more focused on short rounds of data collection followed by off-site data analysis.
“Now, I can get my hands on the laser and collect data to try to understand parameters that allow us to get the specific output we’re looking for,” Abhari says. “I have data that allude me to what those parameters will be, but now in real time, I can be like, ‘If I do this, I see this; if I do that, I see that.’”
In addition to her thesis research, Abhari will be working with her SACLA collaborators on a machine learning project to optimize beam focusing, and helping learn about and improve a portable beam nanofocusing apparatus.