Hung-Wei Tseng, a UC Riverside associate professor of electrical and computer engineering, has laid out a paradigm shift in computer architecture to do just that in a recent paper titled, “Simultaneous and Heterogeneous Multithreading.”

Tseng explained that today’s computer devices increasingly have graphics processing units (GPUs), hardware accelerators for artificial intelligence (AI) and machine learning (ML), or digital signal processing units as essential components. These components process information separately, moving information from one processing unit to the next, which in effect creates a bottleneck.

In their paper, Tseng and UCR computer science graduate student Kuan-Chieh Hsu introduce what they call “simultaneous and heterogeneous multithreading” or SHMT. They describe their development of a proposed SHMT framework on an embedded system platform that simultaneously uses a multi-core ARM processor, an NVIDIA GPU, and a Tensor Processing Unit hardware accelerator.

The system achieved a 1.96 times speedup and a 51% reduction in energy consumption.

“You don’t have to add new processors because you already have them,” Tseng said.

The implications are huge.

Simultaneous use of existing processing components could reduce computer hardware costs while also reducing carbon emissions from the energy produced to keep servers running in warehouse-size data processing centers. It also could reduce the need for scarce freshwater used to keep servers cool.

Tseng’s paper, however, cautions that further investigation is needed to answer several questions about system implementation, hardware support, code optimization, and what kind of applications stand to benefit the most, among other issues.

The paper was presented at the 56th Annual IEEE/ACM International Symposium on Microarchitecture held in October in Toronto, Canada. The paper garnered recognition from Tseng’s professional peers in the Institute of Electrical and Electronics Engineers, or IEEE, who selected it as one of 12 papers included in the group’s “Top Picks from the Computer Architecture Conferences” issue to be published this coming summer.

Gabor Csathy, professor and head of the Department of Physics and Astronomy at the Purdue University College of Science, along with PhD students Haoyun Huang, Waseem Hussain, and recent PhD graduate Sean Myers, led this discovery from the West Lafayette campus of Purdue. Csathy credits lead author Huang as having conceived, led the measurements and writing a large part of the manuscript. All the ultra-low-temperature measurements were completed in Csathy’s Physics Building lab. In his lab they conduct research on strongly correlated electron physics, sometimes referred to as topological electron physics.

Weak interactions of electrons are well established, and the behavior is quite predictable. When electrons interact weakly, the electron is commonly considered the natural building block of the entire system. But when the electrons interact strongly, interpreting the systemic behavior by thinking of individual electrons becomes nearly impossible.

“This occurs in very few instances, like in the fractional quantum Hall regime which we study, for example,” says Csathy. “To explain fractional quantum Hall states, the composite fermion, a very intuitive fundamental building block, comes in different flavors. They can account for a whole subset of the fractional quantum Hall states. But all the fully developed, (i.e topologically protected), fractional quantum Hall states could be accounted for by only two types of composite fermions: the two-flux and four-flux composite fermions. Here we reported a new fractional quantum Hall state that cannot be explained by any of these previous ideas! Instead, we need to invoke the existence of a new type of emergent particle, the so-called six-flux composite fermions. The discovery of new fractional quantum Hall states is scarce enough. However, the discovery of a new emergent particle in condensed matter physics is truly rare and amazing.”

For now, these ideas will be used to expand our understanding of the ordering of the known fractional quantum Hall states into a “periodic table.” It is especially notable to this process that the emergent composite fermion particle is unique in that the electron captures six quantized magnetic flux quanta, forming the most intricate composite fermion known to date.

“The numerology of this complicated physics puzzle requires quite some patience,” says Haoyun Huang, Csathy’s PhD student. “Take the nu=2/3 fractional state as an example. Since 2/3=2/(2*2-1), the nu=2/3 state belongs to the two-flux family. Similarly, for the nu=2/7 fractional state, 2/7=2/(2*4-1), so this state belongs to the four-flux family. In contrast, the fractional states we discovered closely relate to 2/11=2/(2*6-1). Before our work, no fully quantized fractional quantum Hall state was seen that could be associated with six-flux composite fermions. The situation was completely different on the theory front: The existence of these kinds of composite fermions was predicted by Jainendra Jain in his highly influential theory of composite fermions published in 1989. The associated quantization was not observed during these 34 years.”

The material used in this study was grown by a Princeton University team led by Loren Pfeiffer. The GaAs semiconductor electrical quality played a huge role in the success of this research. According to Csathy, this Princeton group is leading the world in growing the highest quality GaAs-based materials.

“The GaAs they grow is very special, as the number of imperfections is astonishingly low,” he says. “The combination of low disorder and the ultra-low-temperature measurement expertise in the Csathy lab made this project possible. One reason we were measuring these samples is that very recently the Princeton group has significantly improved the quality of the GaAs semiconductor, as measured by the tiny amounts of defects present. These improved samples will, for sure, continue to constitute a playground for new physics.”

This exciting discovery is part of ongoing research by Csathy’s team. The team continues to push the limits of discovery in their persistent pursuit of topological electron physics.

Low-temperature measurements in Csathy’s lab were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences program, under Award No. DE-SC0006671. Sample growth efforts of the Princeton team were supported by the Gordon and Betty Moore Foundation Grant No. GBMF 4420 and the National Science Foundation MRSEC Grant No. DMR-1420541.

Researchers used more than a decade of acoustic data to monitor bowhead whales’ movements between their usual overwintering grounds in the Bering Sea and summer feeding grounds in the Chukchi and Beaufort Seas. The whales departed the summer feeding grounds about six weeks later in 2022 than in 2008, based on the acoustic data.

Some are also spending winter farther north in the Chukchi Sea, where commercial traffic in particular has been increasing. That means they could be lingering longer in shipping lanes, which grow busier as sea ice shrinks.

“A shift like this may not necessarily be a bad thing for the whales, but any time we see more overlap with whales and shipping traffic, we should be concerned,” said Angela Szesciorka, a marine scientist at Oregon State University’s Marine Mammal Institute who led the study. “There will be winners and losers, but only time will tell.”

The study was published in Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

Whales on the move

Historically, the population of bowhead whales that Szesciorka studies has spent their winters in the Bering Sea. In April, they’d head north through the Chukchi Sea and into the Beaufort Sea off the Canadian and Alaska coasts, head west to the Russian Chukotka Peninsula, and finally go back south around mid-November. During the 2008-2009 International Polar Year, researchers put an underwater microphone called a hydrophone at the Chukchi Plateau for the first time and were surprised to hear bowhead whales in late spring and summer, much farther north than their previously understood migratory paths.

Traditional knowledge held in Indigenous Arctic communities has suggested the whales’ migration patterns are changing in recent years, and data from a handful of satellite-tagged whales has reflected that. As temperatures warm the waters and sea-ice extent drops, the whole Arctic ecological web is forced to change, from tiny plankton and krill up to whales. Scientists wondered if climate change was behind the shift in bowhead whale migration patterns, but they needed more information on the whales’ migration patterns over time to figure it out.

Szesciorka and her coauthors had previously monitored bowhead whale movements through the Bering Strait using data from hydrophones. They used hydrophones to monitor bowhead whales in the western Beaufort Sea and Chukchi Plateau from 2008 to 2022.

“Bowhead whales are highly vocal,” Szesciorka said. “Males sing pretty much twenty-four-seven from fall through spring, so you know when they’re there.”

The recordings revealed that the whales shifted their winter departure time from the western Beaufort Sea 45 days later in 2022 than they had in 2008. They also spent more time in the summer in the Chukchi Sea, and some appeared to entirely forgo migrating back to the Bering Sea as they normally would.

Some of these changes are most likely due to increased food availability in the Chukchi Sea as a result of warmer waters and declining sea ice, the study suggests. But scientists will need to do more research to know for sure.

“The changes we are seeing in migration patterns lead to many questions,” Szesciorka said. “How many whales are going to the Chukchi Sea in the summer? What are they feeding on? Do the same individuals return each year? We’re essentially learning on the fly how whales are responding to changing climate.”

There’s also concern that Indigenous harvests of bowhead whale could be impacted. Bowhead whales could end up abandoning parts of their historic ranges, leaving some tribes with no access to this traditional food and cultural resource. Having tribal involvement in whale management is critical, Szesciorka said.

Seasonal shifts and ship strikes

Spending more time farther north, where commercial shipping traffic is increasing as sea-ice extent drops, could put the whales at increased risk of hazardous encounters with vessels.

“With this general northward shift paired with an increase in vessels and shipping, the threat of ship strikes will probably increase,” Szesciorka said. Shipping in the western Chukchi Sea has increased about 13% since 2009; however, there hasn’t yet been an increase in bowhead ship-strikes “that we know of,” she emphasized. Ship strikes can only be confirmed during harvests; other whales may die and wash ashore undetected.

But Szesciorka sees opportunity.

“Right now, the Arctic is kind of the wild west,” she said. “As sea ice continues to decline, shipping, especially large commercial vessels that go much faster than smaller fishing boats, is only going to increase. It’s better to start thinking about this sooner rather than later so we can prevent problems rather than try to respond to them.” One solution would be to establish speed limits in bowhead whale seasonal habitat, reducing the risk of ship strikes and noise pollution, she said.

The shift in bowhead whales’ seasonal movements is happening quickly, apace with the other rapid changes in the Arctic. But that’s not necessarily a bad thing. The whales might be nimble enough to keep up with the changes, Szesciorka said.

“We saw these changes in migration patterns in just nine years,” she said. “For a species that can live to 200, that’s pretty stark. That shows they can adapt to their changing environments for now. But will there be a point where they can’t adapt anymore? We have to wait and see.”

The work, led by Penn State Berks Professor of Physics Ruth Daly, was published in the Monthly Notices of the Royal Astronomical Society.

Astronomers call this giant black hole Sagittarius A* (Sgr A*). It is located about 26,000 light-years away from Earth in the center of the galaxy. To determine how quickly Sgr A* is spinning — one of its fundamental properties, along with mass — the researchers applied a method that uses X-ray and radio data to assess how material is flowing towards and away from the black hole. The method was developed and published by Daly in 2019 in The Astrophysical Journal.

“Our work may help settle the question of how fast our galaxy’s supermassive black hole is spinning,” Daly said. “Our results indicate that Sgr A* is spinning very rapidly, which is interesting and has far-reaching implications.”

The team found the angular velocity — the number of revolutions per second — of Sgr A*’s spin is about 60% of the maximum possible value, a limit set because material cannot travel faster than the speed of light.

Past estimations of Sgr A*’s speed have been made with different techniques and by other astronomers, with results ranging from no rotation at all to spinning at almost the maximum rate.

“This work, however, shows that this could change if the amount of material in the vicinity of Sgr A* increases,” Daly said.

As a black hole rotates, it pulls “spacetime” — the combination of time and the three dimensions of space — and nearby matter. The gravitational pull also squashes the spacetime, altering its shape depending on how it’s observed. Spacetime appears circular if the black hole is viewed from the top. From the side, however, the spacetime is shaped like a football. The faster the spin, the flatter the football.

The spin can also serve as an energy source, Daly said, if matter — such as gas or the remnants of a star that wanders too close — exists in the vicinity of the black hole. As the black hole spins, matter can escape in the form of narrow jets called collimated outflows. However, Sgr A* currently has limited nearby matter, so the black hole has been relatively quiet, with weakly collimated outflows, in recent millennia.

“A spinning black hole is like a rocket on the launch pad,” said Biny Sebastian, a co-author from the University of Manitoba in Winnipeg, Canada. “Once material gets close enough, it’s like someone has fueled the rocket and hit the ‘launch’ button.”

This means that in the future, if the properties of the matter and the magnetic field strength close to the black hole change, part of the enormous energy of the black hole’s spin could drive more powerful outflows. This source material could come from gas or from the remnants of a star torn apart by the black hole’s gravity if that star wanders too close to Sgr A*.

“Jets powered and collimated by a galaxy’s spinning central black hole can profoundly affect the gas supply for an entire galaxy, which affects how quickly and even whether stars can form,” said co-author Megan Donahue from Michigan State University. “The ‘Fermi bubbles’ seen in X-rays and gamma rays around our Milky Way’s black hole show the black hole was probably active in the past. Measuring the spin of our black hole is an important test of this scenario.”

Fermi bubbles refer to structures that emit gamma rays above and below the black hole that researchers have theorized resulted from prior massive outflows.

The researchers used the outflow method to determine the spin of Sgr A*. Daly’s approach incorporates consideration of the relationship between the spin of the black hole and its mass, the properties of the matter near the black hole and the outflow properties. The collimated outflow produces the radio waves, while the disk of gas surrounding the black hole emits X-rays. The researchers combined observational data from Chandra and the VLA with an independent estimate of the black hole’s mass from other telescopes to inform the outflow method and determine the black hole’s spin.

“We have a special view of Sgr A* because it is the nearest supermassive black hole to us,” said co-author Anan Lu from McGill University in Montreal, Canada. “Although it’s quiet right now, our work shows that in the future it will give an incredibly powerful kick to surrounding matter. That might happen in a thousand or a million years, or it could happen in our lifetimes.”

In addition to those mentioned above, co-authors include Christopher O’Dea, University of Manitoba, and Daryl Haggard, McGill University.

NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.