Chris Sasaki

Improvements in satellite observation technology over decades made it appear as though Arctic snow cover had increased, but it turns out satellites were actually just better at detecting dwindling amounts

For decades, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) has offered a snapshot of the planet’s changing climate – but University of Toronto researchers have found that some of the underlying data underrepresents a key driver of Arctic warming.

The IPCC reports rely on a wealth of climate data, including observations from the U.S.’s National Oceanic and Atmospheric Administration (NOAA) of autumn snow cover – the extent to which the land is covered by snow – in the Northern Hemisphere. The observations have been made annually since the 1960s.

This metric is critical because, among other roles it plays in the Earth’s climate, snow reflects energy from the planet’s surface back into space. While land and vegetation reflect less than 50 per cent of the energy reaching the surface, snow reflects about 80 per cent.

Aleksandra Elias Chereque (supplied image)

“Snow cover is important because it’s a positive climate feedback mechanism,” explains Aleksandra Elias Chereque, a PhD student in the department of physics in U of T’s Faculty of Arts & Science.

“This is referred to as the snow-albedo effect – albedo meaning reflectivity. Snow loss leads to a decrease in albedo, which leads to higher energy absorption, which, in turn, leads to enhanced snow loss. This is a contributing factor to a phenomenon known as ‘Arctic amplification,’ and it’s why we observe a disproportionate amount of heating in the Arctic.”

However, climate scientists have long questioned the reliability of the NOAA data, noting that the snow cover trends suggested by the data were dramatically inconsistent with other observations and argue they should be treated with caution.

Now, Elias Chereque and her collaborators have validated these concerns through a comprehensive new analysis of the NOAA data.

The NOAA observations showed increases in Northern Hemisphere snow cover of about 1.5 million square kilometres per decade. That’s about 1.5 times the size of the province of Ontario. But the new analysis by Chereque and her colleagues shows snow cover actually decreases by half a million square kilometres per decade, or half the size of Canada’s most populous province.

Elias Chereque and her collaborators show that changes over the years in instrumentation and data collection methods in the NOAA data resulted in an increased sensitivity to thin snow cover and, thus, the erroneous observations that snow cover had increased.

"It’s as if the satellite’s ‘eyeglasses’ got better and better over that period,” says Elias Chereque. “It looks like there’s more snow now than there used to be – but that’s only because the satellite kept getting better ‘prescriptions for its glasses.’ It looked like there was more snow but that’s not what was happening.”

Northern Hemisphere Snow and Ice Chart as of Thursday January 8, 2026 (NOAA)

The study, published in the journal Science Advances, was co-authored by atmospheric physicist Paul Kushner, professor and chair in the department of physics and collaborators from the climate research division of Environment and Climate Change Canada. It adds evidence to the finding that snow cover is decreasing throughout the year and increases confidence in that result.

“We know snow loss is influenced by anthropogenic warming and snow loss also creates more potential for warming through the snow-albedo feedback, so we’ve gained a better understanding of this important mechanism of Arctic amplification,” Elias Chereque says.

“Showing how and why the snow cover trend was wrong helps us learn how to use this data set properly when we're estimating past conditions and future trends. And that helps in understanding whether climate models are accurate.

“Developing tools like this help us better understand climate and make better predictions about the future.”

Breakthrough in atomic clock technology promises more precise timekeeping

lanthierj — Tue, 18 Nov 2025 14:54:55 +0000

Breakthrough in atomic clock technology promises more precise timekeeping

lanthierj Tue, 11/18/2025 - 09:54

Faculty of Arts & Science

Cutline

Lower Saxony, Brunswick: Various superstructures, which are parts of an atomic clock, are located in the time laboratory of the Physikalisch-Technische Bundesanstalt (PTB) (photo by Julian Stratenschulte/picture alliance via Getty Images)

Chris Sasaki

Topic

Breaking Research

Department of Physics

Faculty of Arts & Science

Research & Innovation

Subheadline

World's first cryogenic single-ion trap for regulating an atomic clock will enable advances in fundamental science

Physicists at the University of Toronto have developed technology that could power a new generation of optical atomic clocks with the potential to be a hundred times more accurate than those used today.

The new technology would help advance the replacement of legacy cesium clocks that have been in use for decades to define the length of the second and ensure precise timekeeping.

“Accurate measurements of time and frequency underlie our entire system of physical units,” says experimental physicist Amar Vutha. “Therefore, improving the accuracy of timekeeping devices leads to stronger foundations for every physical measurement.”

Vutha is an associate professor in the Faculty of Arts & Science’s department of physics; Takahiro Tow is a PhD student in the department. Building on the contributions of previous team members, they have developed the world's first cryogenic single-ion trap for regulating the accuracy of an atomic clock.

All timekeeping devices rely on a mechanism that generates a consistently repeating interval or “ticking” – whether it’s a swinging pendulum or a vibrating quartz crystal in a wristwatch.

“In every good clock, the periodic event must be stable,” explains Vutha. “It wouldn't do for it to run faster occasionally and then slower.

“In an atomic clock, the ticking is the oscillations of electromagnetic fields in a laser. And the stable periodicity of the laser is ensured by an atom; the quantum vibrations of the atom work like a tuning fork to keep the laser ‘in tune.’”

U of T physicists have built the world’s first cryogenic optical atomic clock — a breakthrough that could redefine timekeeping with unprecedented accuracy. (supplied image)

The first generation of optical atomic clocks used microwave versions of lasers known as masers, regulated by cesium atoms. Newer versions use visible light lasers whose frequencies are more than 100,000 times higher than masers. That faster “tick” makes them magnitudes more precise, with an accuracy measured to 18 decimal places – comparable to measuring the distance from the Earth to the moon within one millionth of a millimetre.

Vutha and Tow’s third-generation atomic clock also uses optical light. Using electromagnetic fields, they trap a single strontium atom that acts as the clock's tuning fork, synchronizing it with the laser to ensure stability and accuracy.

But Vutha notes that, “The regulating atoms in current optical atomic clocks are still perturbed by infrared light – heat – emitted by nearby objects, including the metal vacuum container around it. This limits their accuracy because, if the tuning fork itself goes out of tune, then you no longer have a stable clock.”

Vutha and Tow's breakthrough is to cool the strontium atom to less than five degrees Kelvin, or about five degrees above absolute zero, which eliminates the thermal radiation that currently limits the accuracy of other single-ion clocks.

Perhaps unsurprisingly, updating a function as fundamental as timekeeping has wide-ranging ramifications.

For example, the definition of the standard of current – the ampere – requires measuring the number of electrons that flow through a device within an accurately calibrated time interval. Similarly, one volt is defined fundamentally in terms of the frequency of oscillations produced in a certain device when a voltage difference is applied across it.

“What’s more,” says Vutha, “I would say that the most successful application of the new generation of optical clocks has been to test whether the fundamental constants of nature – the speed of light, Planck's constant, etc. – are themselves constant. Even though we call them constant, we aren’t quite sure.

“So, atomic clocks can be used to check whether these fundamental constants are actually constant. And while that may not be immediately applicable science, it is very fundamental. And there’s just no other way of doing these kinds of experiments than with atomic clocks.”

The math behind the moves: Why a U of T prof was asked to investigate a headline-making chess scandal

Christopher.Sorensen — Thu, 31 Jul 2025 17:29:15 +0000

The math behind the moves: Why a U of T prof was asked to investigate a headline-making chess scandal

Christopher.Sorensen Thu, 07/31/2025 - 13:29

Cutline

There was no reason to assume five-time U.S. chess champion and grandmaster Hikaru Nakamura, pictured, was cheating when he racked up long winning streaks on the online chess site Chess.com, according to an analysis by U of T statistician Jeffrey Rosenthal (photo by Gregor Fischer/picture alliance via Getty Images)

Chris Sasaki

Topic

Our Community

Faculty of Arts & Science

Global

Statistical Sciences

Subheadline

Jeffrey Rosenthal, a professor of statistical sciences, was tapped by Chess.com to investigate allegations that a grandmaster and five-time U.S. champion's winning streaks were illegitimate

Elite chess may carry an air of respectability and intellectual rigour, but that hasn’t stopped players and fans from levelling accusations of cheating and unfair play.

That’s how University of Toronto statistician Jeffrey Rosenthal came to be tapped in 2024 to analyze seemingly unlikely winning streaks racked up by five-time U.S. chess champion and grandmaster Hikaru Nakamura, who goes by the player name Hikaru.

The games in question took place on the online platform Chess.com, which hosts some 10 million matches every day.

Professor Jeffrey Rosenthal (photo by Dee Keilholz)

“When Chess.com asked me to look into it, I was happy to,” says Rosenthal, a professor of probability and statistical computing in the department of statistical sciences in the Faculty of Arts & Science. “It's the sort of opportunity I like because it involves some genuine statistical probability issues. And it was something that was of genuine importance – not just to a small number of statistical scientists, but to large numbers of people around the world.”

Former world chess champion Vladimir Kramnik had raised suspicions about Hikaru’s streaks, pointing to a run of 46 matches in which Hikaru won 45 and drew one. The suspicion stemmed from the belief that online chess carries a higher potential for cheating – for example, by players using chess-playing software – compared to in-person games.

The controversy even made international headlines a few years back, including in the New York Times.

Rosenthal analyzed data provided by Chess.com and, in an August 2024 report featured on the site, concluded that Nakamura’s streaks were well within statistical expectations – meaning it was unlikely he had cheated.

Kramnik responded with a video criticizing the findings. Rosenthal then addressed Kramnik’s concerns in another report in September 2024 and, in April 2025, published a paper in the Harvard Data Science Review.

In particular, Rosenthal identified two key reasons why Nakamura’s winning streaks on Chess.com didn't indicate foul play.

The first reason was that Nakamura’s opponents were significantly less skilled. For example, during a particular 116-game streak, Nakamura’s player rating averaged 3,017 – a very high score – while his opponents averaged just 1,526.

In other words, because Nakamura was far more skilled than his opponents, long winning streaks were statistically more likely than if he’d faced strong players.

Second, Rosenthal demonstrated that the sheer volume of games Nakamura played increased the likelihood of streaks.

As he explains in his April 2025 paper, if you flip a coin 12 times, the odds of getting 12 heads in a row are extremely low. But if you flip that same coin 10,000 times, the chance of hitting a streak of 12 heads becomes much higher.

Rosenthal demonstrated this by using a Monte Carlo simulation – a computer program that, in this case, flipped a virtual coin 10,000 times. Run 1,000 times for statistical rigour, the simulation showed a nearly 70 per cent chance of producing a 12-head streak, making it far from improbable.

This helped answer one of Kramnik’s questions: Why does Nakamura have 21 long winning streaks, while Magnus Carlsen, the Norwegian grandmaster and multiple world champion, had only one during the same period?

Rosenthal’s explanation: Nakamura played 57,421 games compared to Carlsen’s 5,104 and Nakamura’s opponents were rated much lower than Carlsen’s.

“Just because something is striking and dramatic doesn't necessarily mean that it has statistical significance,” says Rosenthal.

“In order to truly understand what’s going on, you have to stop and think. You have to do the work to figure out the probabilities of something like that happening. It’s how we understand what is and isn’t true.”

It wasn’t the first time Rosenthal had been asked to look into high-profile cheating claims.

In 2006, CBC journalists asked for his help in examining why Ontario retailers were winning a seemingly disproportionate number of lottery prizes. Rosenthal’s analysis confirmed retailers were indeed winning far more than statistical odds would suggest. The revelations ultimately led to criminal charges, jail terms, the dismissal of the Ontario Lottery and Gaming Corporation’s chief executive and the introduction of safeguards still in place today.

Researchers develop new model to explore 'unsolved' phenomenon of turbulence

Christopher.Sorensen — Mon, 26 May 2025 13:25:26 +0000

Researchers develop new model to explore 'unsolved' phenomenon of turbulence

Christopher.Sorensen Mon, 05/26/2025 - 09:25

Cutline

The Phantom Galaxy (M74) as seen by the James Webb Space Telescope (photo by ESA/Webb, NASA & CSA, J. Lee and the PHANGS-JWST Team)

Chris Sasaki

Topic

Breaking Research

Faculty of Arts & Science

Research & Innovation

Space

Subheadline

"Turbulence is ubiquitous: from swirling milk in our coffee to chaotic flows in the oceans, solar wind, interstellar medium – even the plasma between galaxies"

Turbulence can be found everywhere – from the contents of a coffee cup to intergalactic space.

But for scientists, it’s also a bit of a mystery.

“Turbulence remains one of the greatest unsolved problems in classical mechanics,” says James Beattie, a postdoctoral researcher at the Canadian Institute for Theoretical Astrophysics in the University of Toronto’s Faculty of Arts & Science, who also holds a joint appointment at Princeton University. “This despite the fact that turbulence is ubiquitous: from swirling milk in our coffee to chaotic flows in the oceans, solar wind, interstellar medium – even the plasma between galaxies.

“The key distinction in astrophysical environments is the presence of magnetic fields, which fundamentally alter the nature of turbulent flows,” he says.

James Beattie (supplied image)

Beattie is lead author of a new paper in the journal Nature Astronomy describing the computer simulation he and collaborators have developed to study, in unprecedented detail, magnetism and turbulence in the interstellar medium (ISM) – the vast ocean of gas and charged particles that lies between stars in the Milky Way galaxy.

The model is the most powerful to date, requiring the computing capabilities of the SuperMUC-NG supercomputer at the Leibniz Supercomputing Centre in Germany.

It directly challenges our understanding of how magnetized turbulence operates in astrophysical environments. Beattie is hopeful it will provide new insights into the ISM, the magnetism of the Milky Way Galaxy as a whole, and astrophysical phenomena such as star formation and the propagation of cosmic rays.

“This is the first time we can study these phenomena at this level of precision and at these different scales,” says Beattie.

The paper was co-authored with researchers from: Princeton University; Australian National University; the Australian Research Council Center of Excellence in All-Sky Astrophysics; Universität Heidelberg; the Center for Astrophysics, Harvard & Smithsonian; Harvard University; and the Bavarian Academy of Sciences and Humanities.

A composite image of the Phantom Galaxy and (inset) a high-resolution simulation of galactic turbulence with magnetic field lines in white (photo by ESA/Webb, NASA & CSA, J. Lee and the PHANGS-JWST Team; Acknowledgement: J. Schmidt; Simulation: J. Beattie)

While there are far fewer particles in interstellar space than in ultra-high vacuum experiments on Earth, their motions are sufficient to generate a magnetic field – much like how the motion of Earth’s molten core generates our planet’s field.

And although the galactic magnetic field is millions of times weaker than a fridge magnet, it remains one of the forces that shapes the cosmos.

At its largest scale, the model can improve our understanding of the Milky Way’s overall magnetic field. When scaled down, it can help astronomers better understand more “compact” processes, such as the solar wind that streams outward from the sun and greatly affects Earth.

Thanks to its higher resolution, the model also has the potential to deepen our understanding of star formation. "We know that magnetic pressure opposes star formation by pushing outward against gravity as it tries to collapse a star-forming nebula,” says Beattie. “Now we can quantify in detail what to expect from magnetic turbulence on those kinds of scales.”

In addition to its higher resolution and scalability, the model also marks a significant advance by simulating the dynamic changes in the density of the ISM – from an incredibly tenuous near-vacuum to the higher densities found in star-forming nebulas.

“What our simulation captures really well,” says Beattie, “is the extreme changes in density of the ISM – something previous models hadn't taken into account.”

As he develops the next generation of the model with even higher resolution, Beattie is testing it against data collected from observations of the sun-Earth system.

“We've already begun testing whether the model matches existing data from the solar wind and the Earth – and it’s looking very good,” says Beattie. “This is very exciting because it means we can learn about space weather with our simulation. Space weather is very important because we’re talking about the charged particles that bombard satellites and humans in space and have other terrestrial effects.”

Beattie says the new model arrives at a time of growing interest in astrophysical turbulence, alongside a surge in observations of the ISM. As new instruments such as the Square Kilometre Array (SKA) Observatory come online – with the ability to measure fluctuations in turbulent magnetic fields across the galaxy in great detail – accurate theoretical frameworks for interpreting magnetic turbulence will become even more critical.

One of the things that draws Beattie to this research is its elegant consistency.

"I love doing turbulence research because of its universality,” he says. “It looks the same whether you’re looking at the plasma between galaxies, within galaxies, within the solar system, in a cup of coffee or in Van Gogh’s The Starry Night.

“There’s something very romantic about how it appears at all these different levels and I think that’s very exciting.”

Researchers explore how fisheries affect child development

Christopher.Sorensen — Fri, 21 Feb 2025 19:39:25 +0000

Researchers explore how fisheries affect child development

Christopher.Sorensen Fri, 02/21/2025 - 14:39

Cutline

Fish vendors buy silver cyprinid, or omena, from fishermen in Western Kenya (photo by SIMON MAINA/AFP/Getty Images)

Chris Sasaki

Topic

Global Lens

Faculty of Arts & Science

Global

Research & Innovation

School of the Environment

Sustainability

Subheadline

Study finds eating a native, sardine-like fish leads to better child development outcomes in Kenya than consuming Nile perch

With a focus on Kenya, researchers from the University of Toronto are exploring how child development – including muscle movement, language skills, emotional responses and social interactions – is improved by fish consumption and, indirectly, by fisheries-generated income.

The study, published recently in the journal World Development, looked at communities on Kenya’s Mfangano Island on Lake Victoria, which is home to some 30,000 residents.

They found that the consumption of a native, sardine-like species called omena (Rastrineobola argentea) – a historically underexploited species – leads to better child development outcomes than consumption of Nile perch, an invasive species introduced to the lake in the 1960s. That’s likely because omena contain higher levels of micronutrients such as omega-3 fatty acids, iron, zinc and calcium.

“Understanding the different pathways linking fishery access and early childhood development is key to designing a more comprehensive approach to tackling the effects of changes in fishery access on human well-being,” says Ranaivo Rasolofoson, an assistant professor of planetary health in the Faculty of Arts & Science’s School of the Environment and lead author of the paper.

While Nile perch are popular commercially because they are large, fleshy and have fewer bones, the researchers found no significant benefits for child development outcomes. Nile perch are also an invasive predator that has had a significant impact on the lake’s ecosystem and, since they are higher up the food chain, Nile perch typically contain more environmental contaminants.

The researchers also show that past studies into the benefits of fisheries on the lake did not adequately take into account the positive indirect impact of fisheries on child development. They show that fisheries income – either through the sale of caught fish or working at processing plants – also improves child development outcomes by improving families’ overall diets.

While the authors did not fully investigate the pathways between income and benefits to children, they point out that fishing income can affect early childhood development in many ways, including by enhancing parents’ mental health and parenting behavior, and by making school-related expenses and enrichment items like books and toys more affordable. It may also help by reducing parental stress and ameliorating harsh, authoritative and unresponsive parenting brought on by economic hardship.

“There's a lot of research that shows fish consumption is good for child development,” says Rasolofoson. “To my knowledge, our study is the first to quantify the contribution of fishing income alongside that of fish consumption on child development.”

Rasolofoson, who began the study as a postdoctoral researcher at Cornell University, co-authored the paper with researchers from the United States Agency for International Development, the Ekialo Kiona Center in Kenya, the Kenya Marine and Fisheries Research Institute, and the University of California, Berkeley.

The study included 210 children aged two and under from 206 households that both consumed fish and gained income from fisheries. Subjects were surveyed nine times over two years.

Rasolofoson is hopeful the findings will help guide public policy. As the authors point out, disentangling the pathways between fish consumption, fisheries-related income and health is critical in developing effective programs and policies for improving nutrition, early childhood development and nature conservation.

“My hope is that decision-makers will see the research and realize that locally available, non-invasive, environmentally friendly species like omena can be very nutritious,” he says. “That could lead to, for example, sustainable management of these species and their promotion as part of a healthy diet.”

As a professor of planetary health, this study is just one facet of Rasolofoson’s overall research.

“Planetary health is about the impact that environmental or natural system degradation has on human health,” he says. “In other words, what is the impact of climate change, heat waves, more intense and frequent storms or deforestation?

“This research looks at the connection between aquatic systems and human health. It’s a small piece of the big picture but we think it’s an important contribution.”

Researchers' lab technique could speed forensic analysis in sexual assault cases

Christopher.Sorensen — Tue, 17 Sep 2024 14:43:28 +0000

Researchers' lab technique could speed forensic analysis in sexual assault cases

Christopher.Sorensen Tue, 09/17/2024 - 10:43

Cutline

(photo by Science Photo Library/Getty Images)

Chris Sasaki

Topic

Breaking Research

Centre for Research and Applications in Fluidic Technologies

Institute of Biomedical Engineering

Donnelly Centre for Cellular & Biomolecular Research

Chemistry

Faculty of Arts & Science

Research & Innovation

U of T Mississauga

A team of researchers has developed a new approach to analyzing DNA evidence in sexual assault cases – one that could reduce lengthy delays in the processing of evidence.

While there are almost half a million sexual assaults in Canada every year, many more go unreported because victims are reluctant to come forward.

One of the reasons cited by victims is that analysis of forensic evidence is too slow.

Mohamed Elsayed (supplied image)

“For this research, we read reports and surveys that asked victims why they weren’t reporting assaults,” says the study’s lead author Mohamed Elsayed, who worked on the project as part of his PhD in biomedical engineering at the University of Toronto. “And the most common answer was that they didn't have confidence in the justice system – and that lack of confidence was partly because of how long the process takes.”

Elsayed, now a post-doctoral researcher in the department of chemistry in the Faculty of Arts & Science, co-authored the study with, among others, Leticia Bodo, a master’s student in the department of chemistry, and Aaron Wheeler, a professor in the department of chemistry, the Institute of Biomedical Engineering and the Centre for Research and Applications in Fluidic Technologies, a U of T institutional strategic initiative.

All three researchers are also affiliated with the Donnelly Centre for Cellular and Biomolecular Research.

Processing forensic evidence in sexual assault cases is a technical, multi-step process that involves collecting DNA evidence and sending it to a well-equipped forensic laboratory for analysis by a skilled technician. Once there, the sample is first processed to isolate the assailant’s DNA from the victim’s so the assailant’s DNA can then be analyzed and used to identify a suspect.

The entire process can take days, weeks or longer. Most of that time is taken up with transporting the evidence to the lab, where its analysis can be further delayed depending on how many other cases are being investigated.

To speed things up, researchers focused on the first step: separating two individuals’ DNA from a single sample. At present, this is usually done manually by trained and experienced experts.

Elsayed and his collaborators, by contrast, developed a process called ’differential digestion” using digital microfluidics that helped simplify the overall process and reduce the number of manual steps needed to isolate the assailant’s DNA from 13 to five. “Also, because micro-fluidic processes tend to be faster, we expect that one of the eventual benefits will be shortening the overall time needed,” says Elsayed.

What’s more, the new approach could lead to a mobile solution that no longer requires a lab. For example, testing could be done at a hospital, circumventing the lab’s queue.

The new technique, described in a paper published in the journal Advanced Science, is compatible with the technology known as Rapid DNA analysis that is already in use for the second step of identifying an individual from their DNA. The study’s authors, which included researchers from U of T Mississauga’s forensic science program, say the long-term goal is to integrate the two technologies to make the process even more streamlined.

While there remain several challenges to deploying the new technique, Elsayed says he is confident they can be overcome and has turned his efforts toward making it widely accessible and commercially viable.

“Our plan is to develop an instrument that will do in five minutes what currently takes 45,” says Elsayed. “And to run many more samples than previously. Once we do that, the next step would be to introduce the technology to forensic labs and hospitals.

“It will take years, but the potential is very exciting.”

The research was supported by the ANDE Corporation and NSERC Alliance Society.

"I’m grateful to NSERC for having the foresight to establish the ‘Alliance Society’ program which has a mission to ‘address a societal challenge that will result in new natural sciences and engineering knowledge and societal impact,” Wheeler says.

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Forensic Science

Supermassive black hole mergers could be explained by dark matter: Study

Christopher.Sorensen — Tue, 06 Aug 2024 15:35:00 +0000

Supermassive black hole mergers could be explained by dark matter: Study

Christopher.Sorensen Tue, 08/06/2024 - 11:35

Cutline

A visualization of two supermassive black holes in orbit around each other (image by NASA's Goddard Space Flight Center/Scott Noble; simulation data, d'Ascoli et al. 2018)

Chris Sasaki

Topic

Breaking Research

Department of Physics

Faculty of Arts & Science

Research and Innovation

Space

Subheadline

A team of researchers that includes a U of T postdoc may have solved the "final parsec problem" of astrophysics

A team of astrophysicists that includes the University of Toronto’s Gonzalo Alonso-Álvarez has shown that pairs of supermassive black holes can merge together into a single, larger black hole – a major breakthrough in addressing what is known as the "final parsec problem."

Gonzalo Alonso-Álvarez (supplied image)

The longstanding astrophysics problem refers to a discrepancy between the detection of gravitational signals permeating the universe – which astrophysicists previously hypothesized had emanated from millions of merging pairs of supermassive black holes (SMBHs) – and theoretical simulations which showed that the approach of SMBHs stalls when they’re roughly one parsec (about three light years) apart.

Not only did the final parsec problem conflict with the theory that merging SMBHs were the source of the gravitational wave background, it was also at odds with the theory that SMBHs – each billions of times more massive than our Sun – grow from the merger of less massive black holes.

The new research, published in Physical Review Letters, has shown that pairs of SMBHs can indeed break through the one-parsec barrier and merge into a single black hole. This is demonstrated by calculations showing that SMBHs continue to draw closer because of previously overlooked interactions with particles within the vast cloud of dark matter surrounding them.

“We show that including the previously overlooked effect of dark matter can help supermassive black holes overcome this final parsec of separation and coalesce,” says Alonso-Álvarez, a post-doctoral fellow in the department of physics at U of T’s Faculty of Arts & Science and the department of physics and Trottier Space Institute at McGill University, who is first author on the paper. “Our calculations explain how that can occur, in contrast to what was previously thought.”

SMBHs are thought to lie in the centres of most galaxies. When two galaxies collide, the SMBHs fall into orbit around each other; as they revolve around each other, the gravitational pull of nearby stars tugs at them and slows them down, causing them to spiral inward toward a merger.

Previous merger models showed that when the SMBHs approached to within roughly a parsec, they begin to interact with the dark matter cloud or halo in which they are embedded. These models indicated that the gravity of spiraling SMBHs throws dark matter particles clear of the system.

The new model introduced by Alonso-Álvarez and co-authors James Cline, a professor at McGill University and the European Organization for Nuclear Research (CERN) in Switzerland, and Caitlyn Dewar, a graduate student at McGill, reveals that dark matter particles interact with each other in such a way that they are not dispersed. The density of the dark matter halo remains high enough that interactions between the particles and the SMBHs continue to degrade the SMBH’s orbits – clearing a path to a merger.

“The possibility that dark matter particles interact with each other is an assumption that we made, an extra ingredient that not all dark matter models contain,” says Alonso-Álvarez. “Our argument is that only models with that ingredient can solve the final parsec problem.”

The background hum generated by these colossal cosmic collisions is made up of gravitational waves of much longer wavelength than those first detected in 2015 by astrophysicists operating the Laser Interferometer Gravitational-Wave Observatory (LIGO). Those gravitational waves were generated by the merger of two black holes, both some 30 times the mass of the Sun.

The background hum has been detected in recent years by scientists operating the Pulsar Timing Array. The array reveals gravitational waves by measuring minute variations in signals from pulsars, rapidly rotating neutron stars that emit strong radio pulses.

In addition to providing insight into SBMH mergers and the gravitational wave background signal, the new result also provides a window into the nature of dark matter. “Our work is a new way to help us understand the particle nature of dark matter,” says Alonso-Álvarez. “We found that the evolution of black hole orbits is very sensitive to the microphysics of dark matter and that means we can use observations of supermassive black hole mergers to better understand these particles.”

For example, the researchers found that the interactions between dark matter particles they modeled also explains the shapes of galactic dark matter halos.

“We found that the final parsec problem can only be solved if dark matter particles interact at a rate that can alter the distribution of dark matter on galactic scales,” says Alonso-Álvarez.

“This was unexpected since the physical scales at which the processes occur are three or more orders of magnitude apart. That’s exciting.”

16-year-old physics grad completes ‘incredible journey’ at U of T

Christopher.Sorensen — Mon, 03 Jun 2024 15:33:09 +0000

16-year-old physics grad completes ‘incredible journey’ at U of T

Christopher.Sorensen Mon, 06/03/2024 - 11:33

Cutline

Daniel Honciuc Menendez, 16, is the youngest to graduate from the Faculty of Arts & Science, U of T Scarborough or U of Mississauga since at least 1979 (photo by Diana Tyszko)

Chris Sasaki

Topic

Our Community

Convocation 2024

Faculty of Arts & Science

International Students

Physics

University College

Subheadline

Daniel Honciuc Menendez carried out research on dark matter detection and theoretical quantum optics

Daniel Honciuc Menendez was 11 years old when he took part in a summer program in theoretical physics at the Perimeter Institute in Waterloo, Ont., in 2019.

“I’d known for a long time that I wanted a career in physics. But it was in this program that I learned for sure that this was what I wanted to do with my life,” says Honciuc Menendez, who is Ecuadorean and was living in the country's capital Quito at the time.

The trip was his first visit to Canada – and made a big impression. “I liked the openness of the people and the diversity. So I decided that when I applied to universities, I would make sure to apply to universities in Canada.”

After completing high school at age 12, Honciuc Menendez received offers of admission from 12 post-secondary institutions in Canada, the U.S. and Ecuador. He chose the University of Toronto, where he received an International Scholars Award, and began his undergraduate studies as a member of University College.

Honciuc Menendez at 11 years old at the launch of one of his experiments on a rocket with the NASA Cubes in Space program at the Wallops Flight Facility (photo courtesy Daniel Honciuc Menendez)

Now 16 years old, Honciuc Menendez is graduating with a specialist in physics and a major in mathematics with high distinction. He’s the youngest to graduate from the Faculty of Arts & Science, U of T Scarborough or U of T Mississauga since at least 1979, the year the university began tracking such data.

“I’m proud and excited to be graduating,” he says. “It’s the culmination of four years of hard work, research and volunteer experiences. I’m really looking forward to convocation.”

Faculty of Arts & Science writer Chris Sasaki spoke to Honciuc Menendez before his convocation.

When did your interest in science begin?

I started reading at an early age. When I was very young, my mother and I moved often to different countries because of her career. During this time, I was surrounded by a variety of books, including math books, puzzle books, encyclopedias and atlases. They became my early companions and mentors. Also, even before starting school, I was captivated by educational videos, websites and apps about math, physics, chemistry and other subjects. Then, at 4 years old, while living in the U.K., I gained early entrance into grade school and became interested in programming and robotics. I attended every science festival I could. It became clear to me that I wanted to pursue a life in the sciences.

What was your early education like?

Early entrance into grade school in the U.K. was my first ‘grade-skip.’ When I was six years old, we moved back to Ecuador and I wanted to learn more challenging material during my classes. After meetings with my new school, I was encouraged to apply to the Johns Hopkins University (JHU) Centre for Talented Youth. Upon passing the entrance tests, I was admitted into the program, which allowed me to take advanced courses.

At nine years old, I skipped another grade and started auditing International Baccalaureate (IB) diploma classes in physics and music. Then, when I was 10 years old, I also took the SAT and with its results, I was allowed to skip four more grades to 11th grade and was also able to join other programs like JHU’s Study of Exceptional Talent. From there, I took a full IB diploma program and graduated from high school at 12 years old.

What research projects were you able to take part in at U of T?

The first was with Professor Miriam Diamond in dark matter detection with the Super Cryogenic Dark Matter Search experiment at SNOLAB, an underground research facility near Sudbury for neutrino and dark matter studies. I developed and tested dark matter detector simulations and conducted data analysis on remote servers.

The second was in theoretical quantum optics with Professor John Sipe at the Centre for Quantum Information & Quantum Control, in which I investigated the theoretical optical response for waveguide-quantum dot systems that could be used as the basis for optical quantum computers.

Throughout both experiences, the collaborative and inclusive spirit of the physics community really inspired me. The professors and researchers provided invaluable mentorship to me and have significantly shaped my decision to pursue a physics research career involving high-energy physics and quantum information.

Honciuc Menendez pursued his interest in music with the Hart House Chamber Strings ensemble (photo courtesy Daniel Honciuc Menendez)

What field are you most interested in now?

I’m interested in quantum information and high-energy physics. Quantum information is a unique field that has applications to various disciplines, since quantum computers can solve various problems that classical computers cannot. I want to specialize in quantum algorithms since they’re essential to realizing the potential of quantum information in its applications, including in my other field of interest, high-energy physics. The more I learn about quantum information's capabilities and its synergy with high-energy physics, the more I realize the significant impact these technologies could have on our understanding of the universe and on advancing computational sciences.

What are your plans after graduation?

I was honored to receive a full scholarship from the European Union to pursue a master's of science in physics with a concentration in quantum science and technology. The program will take place over two years at the Sapienza University of Rome in Italy, then at Université Paris-Saclay in France, and lastly at U of T. I’ll be taking courses and developing my career in quantum technology in academia and industry, and exploring the interdisciplinary possibilities of the quantum science landscape, including in high-energy physics, medicine, cybersecurity and finance. Later, I want to pursue a PhD in physics where I can go deeper into the intersection between quantum information and high-energy physics.

What are your thoughts as you look back at the past four years?

Throughout these years, the support from my friends, professors and mentors at U of T, and the resources provided by University College and U of T’s Accessibility Services have been invaluable and have helped me navigate the complexities of academic life and the personal challenges of being a young student. Plus, all of this would not have been possible without the unconditional support from my mother, a single mom who has been my constant source of strength and inspiration, and who accompanied me as I pursued my studies in Canada.

These past four years have been transformative for me — not just academically but also personally — and were filled with challenges, achievements and growth. It’s been an incredible journey, and I step forward with a heart full of gratitude for the U of T community, ready for the next chapter of my life.

U of T researchers identify 'degrees of Kevin Bacon' gene in fruit flies

rahul.kalvapalle — Fri, 24 May 2024 20:22:51 +0000

U of T researchers identify 'degrees of Kevin Bacon' gene in fruit flies

rahul.kalvapalle Fri, 05/24/2024 - 16:22

Cutline

(photo by janeff/iStock)

Chris Sasaki

Topic

Breaking Research

Ecology & Evolutionary Biology

Faculty of Arts & Science

Genes

Genetics

Research & Innovation

U of T Mississauga

Subheadline

Researchers studied two distinct strains of fruit flies and found that one group showed different patterns of connections within their networks

A team of researchers from the University of Toronto has identified a gene in fruit flies that regulates the types of connections between flies within their “social network.”

The researchers studied groups of two distinct strains of Drosophila melanogaster fruit flies and found that one strain showed different types or patterns of connections within their networks than the other strain.

The connectivity-associated gene in the first strain was then isolated. When it was swapped with the other strain, the flies exhibited the connectivity of the first strain.

Researchers named the gene after Hollywood star Kevin Bacon (photo by Theo Wargo/Getty Images)

The researchers named the gene “degrees of Kevin Bacon” (dokb), for the prolific Hollywood star of such films as Footloose and Apollo 13. Bacon’s wide-ranging connections to other actors is the subject of the parlour game called “The Six Degrees of Kevin Bacon,” which plays on the popular idea that any two people on Earth can be linked through six or fewer mutual acquaintances.

“There's been a lot of research around whether social network structure is inherited, but that question has been poorly understood,” says Rebecca Rooke, a post-doctoral fellow in the department of ecology and evolutionary biology in the Faculty of Arts & Science and lead author of the paper, published in Nature Communications. “But what we’ve now done is find the gene and proven there is a genetic component.”

The work was carried out as part of Rooke’s PhD thesis in Professor Joel Levine’s laboratory at U of T Mississauga before he moved to the department of ecology and evolutionary biology, where he is currently chair.

“This gives us a genetic perspective on the structure of a social group,” says Levine. “This is amazing because it says something important about the structure of social interactions in general and about the species-specific structure of social networks.

Post-doctoral researcher Rebecca Rooke (supplied image)

“It's exciting to be thinking about the relationship between genetics and the group in this way. It may be the first time we’ve been able to do this.”

The researchers measured the type of connection by observing and recording on video groups of a dozen male flies placed in a container. Using software previously developed by Levine and post-doctoral researcher Jon Schneider, the team tracked the distance between flies, their relative orientation and the time they spent in close proximity. Using these criteria as measures of interaction, the researchers calculated the type of connection or “betweenness centrality” of each group.

Rooke, Levine and their colleagues point out that individual organisms with high betweenness centrality within a social network can act as “gatekeepers” who play an important role in facilitating interactions within their group.

Gatekeepers can influence factors like the distribution of food or the spread of disease. They also play a role in maintaining cohesion, enhancing communication and ensuring better overall health of their group.

In humans, betweenness centrality can even affect the spread of behaviours such as smoking, drug use and divorce.

Professor Joel Levine (supplied image)

At the same time, the researchers point out that social networks are unbiased and favour neither “good” nor “bad” outcomes. For example, high betweenness centrality in a network of scientists can increase potential collaborators; on the other hand, high betweenness centrality in another group can lead to the spread of a disease like COVID-19.

“You don't get a good or a bad outcome from the structure of a network,” explains Levine. “The structure of a network could carry happiness or a disease.”

Rooke says an important next step will be to identify the overall molecular pathway that the gene and its protein are involved in “to try to understand what the protein is doing and what pathways it’s involved in – the answers to those questions will really give us a lot of insight into how these networks work.”

And while the dokb gene has only been found in flies so far, Rooke, Levine and their colleagues anticipate that similar molecular pathways between genes and social networks will be found in other species.

“For example, there's a subset of cells in the human brain whose function relates to social experience – what in the popular press might be called the ‘social brain,’” says Levine.

“Getting from the fly to the human brain – that's another line of research. But it almost has to be true that the things that we're observing in insects will be found in a more nuanced, more dispersed way in the mammalian brain.”

Students tackle impact of climate change at U of T Climate Impacts Hackathon

Christopher.Sorensen — Mon, 06 May 2024 16:44:57 +0000

Students tackle impact of climate change at U of T Climate Impacts Hackathon

Christopher.Sorensen Mon, 05/06/2024 - 12:44

Cutline

Students, instructors and organizers participate in the inaugural Climate Impacts Hackathon (photo by Milan Ilnyckyj, CC BY-NC-SA 2.0 DEED)

Chris Sasaki

Topic

Our Community

Climate Positive Energy

Data Sciences Institute

Institutional Strategic Initiative

Climate Change

Faculty of Applied Science & Engineering

Faculty of Arts & Science

Undergraduate Students

Subheadline

Teams of undergraduate and graduate students grappled with problems that ranged from altering irrigation practices in Sudan to adapting snow-clearing plans in Ottawa

In the wake of Toronto’s warmest winter on record, students at the University of Toronto recently gathered for the inaugural U of T Climate Impacts Hackathon.

The event asked students to tackle several challenges brought by a warming planet: How should the City of Ottawa adapt its snow clearing plan in response to increased precipitation caused by our warming atmosphere? How should irrigation practices in Sudan change in response to higher temperatures and reduced rainfall? And where should new cooling stations – swimming pools, libraries, community centres, shopping malls – be located in an increasingly sweltering City of Toronto?

Participants included undergraduate and graduate students from a range of natural science and engineering disciplines, as well as from the humanities and social sciences. They were divided into teams and competed for prizes.

The hackathon was led by Paul Kushner, a professor of Earth, atmospheric and planetary physics in the department of physics in the Faculty of Arts & Science; and Karen Smith, an associate professor, teaching stream, in the department of physical and environmental sciences (DPES) at U of T Scarborough. Co-organizers included Michael Morris, a PhD candidate in the department of physics, and Francisco Camacho, a masters of environmental science student at DPES.

The event was hosted by the department of physics and the DPES; sponsors included Climate Positive Energy (CPE) – a U of T institutional strategic initiative – the Centre for Climate Science and Engineering (CSE) and the Cosmic Future Initiative.

The event kicked off with a wide-ranging discussion from a panel of climate experts with diverse perspectives.

Steve Easterbrook, director of the School of the Environment in the Faculty of Arts & Science, spoke about how climate models work and why we can trust them. Lisa MacTavish, project lead in resilience, climate resilience policy and research for the City of Toronto, shared how the city uses climate projections to manage infrastructure and crisis planning. And Daniel Posen, an associate professor in the department of civil and mineral engineering in the Faculty of Applied Science & Engineering, talked about his expertise at the intersection of climate change and engineering.

To develop their solutions, students used the University of Toronto Climate Downscaling Workflow (UTCDW) which includes the UTCDW Guidebook developed by Morris, Smith and Kushner, and the UTCDW Survey, a project design tool. The UTCDW was developed with the support of the CSE, CPE and the Data Sciences Institute, another U of T institutional strategic initiative.

Climate models or simulations typically work on a global scale; the UTCDW is designed to help researchers “downscale” what the models do in order to understand how smaller regions and even individual cities are being affected by climate change. The resulting projections can then inform decisions on a local level.

“In our proposal for support to develop these tools, we committed to holding this hackathon to roll them out,” says Kushner. “The intent is to encourage a better understanding of climate change impacts on different domains of application in an atmosphere of fun engagement and community cohort building.”

First prize was awarded to a team that tackled the cooling centre challenge. Using the downscaling tool, the team made detailed projections using temperature and humidity data. They considered vulnerable groups including children, the elderly, refugees and the underhoused; and they factored in education and income levels.

After surveying the current locations of the city’s cooling centres, the team came up with recommendations for six new centres located in areas that are currently underserved.

“We were very pleased and impressed at how far the student participants got in their analysis – how they creatively overcame technical and conceptual obstacles, and how they maintained a constructive and positive attitude as they grappled with the serious issues of climate change,” Kushner says.