Neural Networks and Hidden Figures

For physics Ph.D. student Amitava Banerjee, coming to the University of Maryland was a giant step—literally. Banerjee grew up more than 8,000 miles away in Amitava BanerjeeAmitava BanerjeeKolkata, India, with a strong interest in science early on. Both of Banerjee’s parents are physicists, and when he did his undergraduate and master’s work at Presidency University in Kolkata, his own future in physics started coming into focus.

“As I learned more and more, I saw that physics claims it can solve anything in the universe starting from small atoms up to the scale of the full universe and that kind of mission is very, very grand,” Banerjee said. “I feel that if I want to pursue any particular interest, physics will actually help me do that.”

By the time he was ready to begin his doctorate in fall of 2018, Banerjee had done his homework. Though he’d only left India once before, distance was no obstacle. He knew exactly where he wanted to go.

“I was already following the work of many UMD faculty members and I also knew many alumni personally,” Banerjee said. “I felt like I had a connection with them right from the beginning.”

That connection inspired Banerjee and his research, almost from the day he arrived.

“Before coming to UMD I thought that I would be doing work in atomic, molecular and optical physics,” Banerjee recalled. “But I got into working with the Chaos Group led by Professors Edward Ott and Rajarshi Roy and others, and they gave me some problems that I found were too interesting to ignore. So, I started working on them and Professors Ott and Roy became my advisors.”

Now, Banerjee is working to understand real physical systems via computer models made with artificial neural networks that learn to behave like those systems. 

“As of now, we have developed a theoretical framework using machine learning that can tell you how different components of a big system are influencing each other, just by looking at their behavior over time,” Banerjee explained. “Examples of such tasks can be very broad. They include understanding how neurons in the brain are wired together just by observing their firing patterns, or how different genes in some unknown biochemical circuitry turn each other on or off, or understanding how different elements of global climate affect each other only by looking at the weather of several days.”

Banerjee’s hope as he continues to test this framework is that by looking inside neural networks or similar computer models, we may one day be able to better understand, or even predict, useful information about real systems in the physical world.

His research is ongoing, but in March 2020 when the COVID-19 pandemic hit, everything stopped. Labs were off limits and Banerjee had to improvise, recruiting his housemates—physics classmates and an alumnus, Wrick Sengupta (Ph.D. ’16, physics)—and taking his work in a different direction. In a letter to the online magazine Physics, he described the experience.

“We have been able to uncover connections between concepts in vastly different areas of physics,” Banerjee wrote. “When we are not busy collaborating, we share in the housekeeping and eat free-delivery or buy-one-get-one-free pizzas. It also helps to have a Netflix subscription, a good stock of red wine, and someone who can bake cheesecakes.”

While Banerjee was working from home, his focus shifted to trying to create a simplified model for a certain class of plasmas, often difficult to deal with computationally because of their complex interactions. The idea was to map the plasmas to a very different set of systems.

“These systems have traditionally been employed to describe synchronization in the natural world,” Banerjee said. “You have synchronization all around in nature, like fireflies flashing in concert in the evening or crickets chirping together or frogs croaking. We have very nice analytical theory describing synchronizations and we have simple models predicting the emergence of synchronous behavior as seen in nature, so I tried to map plasmas onto those models in order to get a simplified model of plasmas. We’ve been able to take this stuff to a point where it’s too interesting to discontinue.”

Though science and physics drive Banerjee’s research, he also has a strong creative side. When he missed his mother’s cooking after coming to the U.S., he taught himself how to prepare the traditional dishes he grew up with. 

“When I came here, it was kind of a challenge,” he said. “I took it as a challenge, cooking simple foods like rice and curries, and now I can cook fairly good stuff.”

And although he won’t call himself a photographer, Banerjee’s Instagram account features a colorful patchwork of cellphone images, reflecting the simple beauty he sees around him.

“I like capturing simple things in nature, the little things,” he said.

Banerjee’s creative side is also reflected in one of the studies he’s most proud of. Published in 2019 in the journal Chaos: An Interdisciplinary Journal of Nonlinear Science, this work used a neural network model of systems to infer their underlying interaction network—in the form of a picture of meteorologist and mathematician Edward Lorenz.

It was Lorenz’s simple model for atmospheric convections, and computer simulations of that model in the ’60s, which eventually led to a paradigmatic system of chaos theory. And they have been applied to model a variety of other systems since then, like lasers and electric circuits. 

In a sense, Banerjee’s research connected the dots.

“In my work, I have a large number of interconnected Lorenz systems and I try to know how they are interacting using a neural network model of the system,” BanerEdward LorenzEdward Lorenzjee explained. “To make things more interesting, we used a pixelated portrait of Edward Lorenz to construct the interaction pattern for the Lorenz systems. So now our task of recovering those interactions is equivalent to the reconstruction of the portrait of Lorenz. You can readily see how well our technique works for this case.”

Banerjee later learned about an untold part of the Lorenz story—a woman named Ellen Fetter did many of the major calculations for Lorenz’s theories but wasn’t recognized for her work until decades later. To honor Fetter, and others like her, Banerjee repeated the process he tested with the Lorenz image, but used Fetter’s picture instead. fetter copy

“Just as we saw in the movie ‘Hidden Figures,’ many women were involved in the huge computations behind major scientific discoveries, but were never recognized,” Banerjee said. “I thought that with an increasing general interest to diversify physics and recognize the hidden faces behind many famous discoveries, now is a good time to tell the stories of underrepresented people through our ongoing research.”

For Banerjee, sharing these stories feels personal, because it is.

“My mother had a Ph.D. in physics but she had to leave academia when I was born,” Banerjee explained. “At those times it was harder, because in India I don’t think that we had really good childcare facilities. Knowing my mother had to quit academia makes me feel like it’s my obligation to make physics more diverse and more welcoming so more people can join us.”

Promoting gender and racial inclusion and equality in physics and all the sciences is as important to Banerjee as his research. Involved in groups like Women in Physics and inspired by the Black Lives Matter movement, he sees opportunities for change.

“Recently I became interested in working toward making physics more inclusive and also learning about what I should do or should not do to contribute more toward that,” he said.

Where will Banerjee be five years from now? He’s not certain. But he believes with his love for teaching and mentoring, it will probably be somewhere in academia. One thing he knows for sure—he wants to be part of a different kind of future, and not just for physics.

“If you ask people what’s the biggest open problem in physics, they’ll probably tell you it’s quantizing gravity or understanding the nature of dark matter or something like that,” Banerjee said. “But I would say the biggest open question in physics and society at large is how to make us more diverse—because we can’t advance without answering that.”

Written by Leslie Miller

Undergrads Highlight High Energy Physics COVID-19 Relief Efforts

The University of Maryland’s First-Year Innovation & Research Experience (FIRE) program encourages students to delve into research. In one of the FIRE streams, Simulating Particle Detection (SPD), the students explore high-energy physics under the tutelage of Dr. Müge Karagöz, with advising contributions by Prof. Sarah Eno and Associate Prof. Alberto Belloni.  The curriculum focuses on the Compact Muon Solenoid (CMS) experiment of CERN's Large Hadron Collider (LHC). The LHC is also home to the LHCb experiment; UMD physicists collaborate in both.

The 2020 SPD Summer Scholars were Ojo Akinwale, David Bour, Fred Angelo Garcia, Kevin Liang, Drew Melis, Norman Moon, Joao Pereira and Kate Sturge. While the primary focus of the summer program was assessing the performance of the High-Granularity Calorimeter as part of the CMS detector upgrades, the group also wanted to acknowledge the COVID-19 relief efforts made by CERN personnel and the wider high-energy community. Collaborating remotely, they  produced a video describing such efforts.

Watch the video here: https://www.youtube.com/watch?v=vdFZlSFefQY

Goldwater Scholar Scott Moroch Explores Accelerator Physics

Scott Moroch; courtesy of sameScott Moroch

If you’re a student hoping to one day make your mark in the world of scientific research, there are few scholarships more prestigious than the Barry Goldwater Scholarship, which encourages students to pursue advanced study and research careers in the sciences, engineering and mathematics.

Over the last decade, the University of Maryland’s nominations yielded 33 Goldwater Scholarships—the most in the nation—and 13 of those scholarships were awarded to physics majors. 

“It is not surprising that physics has produced more of UMD’s Goldwater Scholars than any other department over the last 10 years,” said Robert Infantino, associate dean of undergraduate education in the College of Computer, Mathematical, and Natural Sciences. Infantino has led UMD’s Goldwater Scholarship nominating process since 2001. “The deep commitment of our physics faculty members to mentor undergraduates on research projects has helped to transform outstanding students like Scott into researchers who significantly advance physics research even as undergraduates and who become nationally competitive scholars for competitions like the Goldwater Scholarship and NSF graduate fellowships.”<

The physics department’s latest Goldwater Scholar is Scott Moroch, who will use the scholarship to begin taking graduate-level courses at UMD, an opportunity he earned by completing all of his undergraduate requirements ahead of schedule. Moroch plans to graduate in December 2020, a full semester early.

“I was really excited when I learned that I got the scholarship because I feel like I've worked really hard and I’ve participated in a lot of research as an undergraduate,” Moroch said. “It felt very rewarding and it gave me the confidence I needed to feel like I can be a leader in the field of accelerator physics and do more research in the future.”

Moroch has been interested in math and science since he was 13 years old, but he became interested in physics in 7th grade after reading an article about a teenager who built his own nuclear fusion reactor. 

“After reading that article, something clicked and I just had to build one of these machines,” he said. 

Moroch and one of his friends spent the next three years doing research and working on creating their own reactor. Creating the type of reactor they were looking to build—a tabletop fusion device—would cost thousands of dollars, so they had to get creative. Moroch saved all of the money he received as gifts on his birthday and holidays, and he reached out to companies that donated scientific equipment or sold it to him at a discount.

“So many of these companies would normally build equipment used at universities or other research institutions, but they loved the idea that we were doing this project and getting involved at such a young age, so we managed to get a lot of equipment donated to the project,” Moroch said. “It was a huge help.”

By the time Moroch graduated high school, he had completed the nuclear fusion device. But he never entered it into a showcase or science fair. He simply did it for the love of physics.

“Physics started as a hobby for me,” Moroch explained. “Some people like fixing cars or collecting things, and I just like conducting different physics experiments for my own personal fulfillment.”

It was that deep-rooted interest in physics that brought Moroch to UMD. For years, he had been following the work of Timothy Koeth, an assistant professor in the Department of Materials Science and Engineering and the Institute for Research in Electronics and Applied Physics. It was Koeth who brought a cyclotron, a type of particle accelerator that won its inventor the 1939 Nobel Prize in physics, to Maryland ahead of Moroch’s freshman year. 

“Professor Koeth moved the cyclotron from Rutgers University in New Jersey to UMD, and that's actually one of the reasons why I chose to come to Maryland,” Moroch said. “I wanted to work on this machine.”

The beams that cyclotrons produce, while potentially dangerous, accomplish wondrous things—killing cancer cells with extreme precision, for instance, or changing atoms into a different element altogether.

“Research accelerators at universities are pushing the boundaries of physics,” Moroch said. “They get bigger and bigger with higher and higher energies.” 

Now, Moroch is working with Koeth to develop a novel cyclotron storage ring for Lockheed Martin. The company is interested in using the technology for a new class of power supplies for aerospace electric propulsion systems that can carry things into the solar system and beyond.

With initial funding from Lockheed, Moroch showed that a cyclotron design could be effective, but it was unstable. So, the company decided to fund a more ambitious project at UMD—where the instabilities could be factored out. Moroch now leads a significant portion of the research team.

“In the past 20 years, I have mentored several dozen undergraduate researchers, and Scott Moroch is the first that has demonstrated the entire cycle of research and brought in substantial research funds,” Koeth said.

Last summer and fall, Moroch led a team of three undergraduates in assembling and upgrading a low-energy storage ring as part of the project, an accomplishment he is most proud of.

“Making that storage ring operational again was my most rewarding work because it was a real team effort,” Moroch said. “Some of my research projects have been individual projects, so it was exciting to have everyone be involved and play a part.”

Moroch will continue his work with Koeth on the cyclotron after graduation before starting graduate school in fall 2021 to earn his Ph.D. in physics. Once he finishes his graduate studies, he hopes to pursue a career in academia.

“I love doing research and I have loved teaching during the semesters that I have been a teaching assistant,” he said. “It's really rewarding to teach students and see them understand the concepts of accelerators for the first time. Several of these students have gone on to work in our research group, so I've gotten to work alongside them and watch them continue to grow and learn. I definitely think becoming a university professor is my ultimate end goal.”

Written by Chelsea Torres

Heaviest Black Hole Merger is Among Three Recent Gravitational Wave Discoveries

Scientists observed what appears to be a bulked-up black hole tangling with a more ordinary one. The research team, which includes physicists from the University of Maryland, detected two black holes merging, but one of the black holes was 1 1/2 times more massive than any ever observed in a black hole collision. The researchers believe the heavier black hole in the pair may be the result of a previous merger between two black holes.

Numerical simulation of two black holes that spiral inwards and merge, emitting gravitational waves. The simulated gravitational wave signal is consistent with the observation made by the LIGO and Virgo gravitational wave detectors on May 21st, 2019 (GW190521). Image Copyright © N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration.

This type of hierarchical combining of black holes has been hypothesized in the past but the observed event, labeled GW190521, would be the first evidence for such activity. The Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration (LSC) and Virgo Collaboration announced the discovery in two papers published September 2, 2020, in the journals Physical Review Letters and Astrophysical Journal Letters.

The scientists identified the merging black holes by detecting the gravitational waves—ripples in the fabric of space-time—produced in the final moments of the merger. The gravitational waves from GW190521 were detected on May 21, 2019, by the twin LIGO detectors located in Livingston, Louisiana, and Hanford, Washington, and the Virgo detector located near Pisa, Italy.Numerical simulation of two black holes that spiral inwards and merge, emitting gravitational waves. The simulated gravitational wave signal is consistent with the observation made by the LIGO and Virgo gravitational wave detectors on May 21st, 2019 (GW190521). Image Copyright © N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration.  Numerical simulation of two black holes that spiral inwards and merge, emitting gravitational waves. The simulated gravitational wave signal is consistent with the observation made by the LIGO and Virgo gravitational wave detectors on May 21st, 2019 (GW190521). Image Copyright © N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration.

“The mass of the larger black hole in the pair puts it into the range where it’s unexpected from regular astrophysics processes,” said Peter Shawhan, an LSC principal investigator and the LSC observational science coordinator. “It seems too massive to have been formed from a collapsed star, which is where black holes generally come from.”

The larger black hole in the merging pair has a mass 85 times greater than the sun. One possible scenario suggested by the new papers is that the larger object may have been the result of a previous black hole merger rather than a single collapsing star. According to current understanding, stars that could give birth to black holes with masses between 65 and 135 times greater than the sun don’t collapse when they die. Therefore, we don’t expect them to form black holes.

“Right from the beginning, this signal, which is only a tenth of a second long, challenged us in identifying its origin,” said Alessandra Buonanno, a College Park professor at UMD and an LSC principal investigator who also has an appointment as Director at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. “But, despite its short duration, we were able to match the signal to one expected of black-hole mergers, as predicted by Einstein’s theory of general relativity, and we realized we had witnessed, for the first time, the birth of an intermediate-mass black hole from a black-hole parent that most probably was born from an earlier binary merger.”

GW190521 is one of three recent gravitational wave discoveries that challenge current understanding of black holes and allow scientists to test Einstein’s theory of general relativity in new ways. The other two events included the first observed merger of two black holes with distinctly unequal masses and a merger between a black hole and a mystery object, which may be the smallest black hole or the largest neutron star ever observed. A research paper describing the latter was published in Astrophysical Journal Letters on June 23, 2000, while a paper about the former event will be published soon in Physical Review D.

“All three events are novel with masses or mass ratios that we’ve never seen before,” said Shawhan, who is also a fellow of the Joint Space-Science Institute, a partnership between UMD and NASA’s Goddard Space Flight Center. “So not only are we learning more about black holes in general, but because of these new properties, we are able to see effects of gravity around these compact bodies that we haven't seen before. It gives us an opportunity to test the theory of general relativity in new ways.”

For example, the theory of general relativity predicts that binary systems with distinctly unequal masses will produce gravitational waves with higher harmonics, and that is exactly what the scientists were able to observe for the first time.

“What we mean when we say higher harmonics is like the difference in sound between a musical duet with musicians playing the same instrument versus different instruments,” said Buonanno, who developed the waveform models to observe the harmonics with her LSC group. “The more substructure and complexity the binary has — for example the masses or spins of the black holes are different—the richer is the spectrum of the radiation emitted”

In addition to these three black hole mergers and a previously reported binary neutron star merger, the observational run from April 2019 through March 2020 identified 52 other potential gravitational wave events. The events were posted to a public alert system developed by LIGO and Virgo collaboration members in a program originally spearheaded by Shawhan so that other scientists and interested members of the public can evaluate the gravity wave signals.

“Gravitational wave events are being detected regularly,” Shawhan said, “and some of them are turning out to have remarkable properties which are extending what we can learn about astrophysics.”

 

 

Watch a numerical simulation here: https://youtu.be/zRmwtL6lvIM

The research paper, “GW190521: A Binary Black Hole Coalescence with a Total Mass of 150 Solar Masses,” was published in Physical Review Letters on September 2, 2020.

The research paper, ”Properties and Astrophysical Implications of the 150 Solar Mass Binary Black Hole Merger GW190521,” was published in Astrophysical Journal Letters on September 2, 2020.

The research paper, “GW190814: Gravitational Waves from the Coalescence of a 23 Solar Mass Black Hole with a 2.6 Solar Mass Compact Object,” was published in Astrophysical Journal Letters on June 23, 2020.

The research paper, “GW190412: Observation of a Binary-Black-Hole Coalescence with Asymmetric Masses,” has been accepted for publication in Physical Review D, and was published on Arxiv on April 17, 2020.

About LIGO and Virgo

LIGO is funded by the NSF and operated by Caltech and MIT, which conceived of LIGO and lead the project. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant commitments and contributions to the project. Approximately 1,300 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. A list of additional partners is available at https://my.ligo.org/census.php

The Virgo Collaboration is currently composed of approximately 550 members from 106 institutes in 12 different countries including Belgium, France, Germany, Hungary, Italy, the Netherlands, Poland, and Spain. The European Gravitational Observatory (EGO) hosts the Virgo detector near Pisa in Italy, and is funded by Centre National de la Recherche Scientifique (CNRS) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in the Netherlands. A list of the Virgo Collaboration groups can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo website at http://www.virgo-gw.eu/.

Original story: https://cmns.umd.edu/news-events/features/4651#overlay-context=departments
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