Department of Physics

Munk School of Global Affairs & Public Policy

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.”

From fighting fungus to improving innovation: U of T researchers lead CIFAR interdisciplinary research programs

Romi Levine — Mon, 29 Apr 2019 16:43:21 +0000

From fighting fungus to improving innovation: U of T researchers lead CIFAR interdisciplinary research programs

Romi Levine Mon, 04/29/2019 - 12:43

Cutline

(From left) U of T's Barbara Sherwood Lollar, Dan Breznitz, Leah Cowen and Aephraim Steinberg are leading CIFAR research programs

Romi Levine

Topic

Our Community

Ontario Impact

CIFAR

Earth Sciences

Faculty of Medicine

Innovation Policy Lab

Molecular Genetics

Political Science

Drug-resistant germs like the fungus Candida auris are making their way into hospitals around the world, stumping scientists who are trying to trace their often-mysterious origins.

But a group of international researchers from a diverse range of disciplines, including microbiology, evolution, food security and immunology, are hoping that by working together they can address the potential harm to humans, wildlife and agriculture.

The newly created program, called Fungal Kingdom: Threats & Opportunities, is co-directed by Leah Cowen, a professor and chair of molecular genetics at the University of Toronto, and Joseph Heitman, a professor and chair of molecular genetics and microbiology at the Duke University School of Medicine. It is one of four research programs led by U of T faculty that make up the new 13-program portfolio of CIFAR, a Canadian-based organization that looks to address some of the world’s most pressing issues through interdisciplinary research.

“Through CIFAR, University of Toronto researchers have been able to engage with a global network of scholars across disciplines and borders to tackle complex challenges,” said Vivek Goel, U of T’s vice-president of research and innovation. “This highlights the international demand for U of T’s expertise in a range of areas – from public policy to geochemistry.”

The other U of T-led CIFAR research programs include:

Innovation, Equity and the Future of Prosperity, co-directed by Dan Breznitz, who is the co-director of the Innovation Policy Lab at U of T’s Munk School of Global Affairs & Public Policy, Susan Helper, an economics professor at Case Western Reserve University, and Amos Zehavi, a professor at Tel Aviv University and a senior associate at the Innovation Policy Lab.
This program is one of two in the social sciences that CIFAR has added this year – the first since 2004.
Earth 4D: Subsurface Science and Exploration, co-directed by University Professor Barbara Sherwood Lollar in U of T’s department of Earth sciences and John Mustard, a professor of Earth, environmental and planetary sciences at Brown University.
Quantum Information Science – a renewed program, co-directed by Aephraim Steinberg, a professor of physics at U of T, and David Poulin, a professor at Université de Sherbrooke.

Breznitz said the CIFAR program gives his research group a platform to look at innovation in a different light. While there are proven benefits that come with innovation – from economic growth to personal well-being – those benefits are not always distributed equally.

The program looks to combine research on innovation technology and distribution – two areas Breznitz said are heavily siloed – in order to create an action plan that leads to meaningful change.

Inequality can take many forms in the innovation sphere, said Breznitz, offering the example of how innovation is funded.

“The main vehicle for financing innovation is venture capital,” he said, adding this usually means giving a small group of people large sums of money in the hopes they can deliver exponential returns.

“What you're really creating is an industry completely obsessed with financial access,” he said. “Those who succeed, the people who basically get the lottery ticket, are people who are already extremely well-off.

“Ninety per cent of people are left out.”

The first step in launching the program will be to create a common language between researchers – a challenge when they come from many different backgrounds like law, engineering, geography, sociology and economics.

“That's going to be both hard and the most fun,” said Breznitz. “I've got a very big, new sandbox to play with.”

Sherwood Lollar's program, Earth 4D, is taking an innovative approach to studying our own planet. It calls for thinking about Earth as we do other planets in our solar system by taking a closer look at how each of its elements interact with one another – from the interior to the surface and into the atmosphere.

“Interestingly, when we think about our own planet, that's not typically the way science has gone about it,” she said. “If you think about the breadth of work we do on this planet, it tends to be: ‘We need to understand this problem over there and that problem over here.’”

Sherwood Lollar’s team will be focusing on four themes: water, and how water resources are being altered by climate change; energy, from the need to drive technology to how subsurface life sustains itself without the sun; the origin and evolution of life on this planet; and the concept of time and how it affects the other themes.

“We decided we really were at a place and point in time where there was an opportunity to transform how we think about Earth,” said Sherwood Lollar.

To do so, she said it was necessary to bring together a group of researchers who not only bring a wide range of expertise, but are at different points in their careers.

“Intergenerational exchange is really important in this group,” she said. “One of the things I love about it is we're already seeing people who didn't know each other, and didn’t work together, coming together to do this kind of work.

“CIFAR is a very unique and effective agent in the Canadian intellectual and research landscape because their mandate is specifically to try to bring together [researchers in] pursuit of big fundamental questions that have been wrestled with across the board – by society, by science, by engineering, by humanities – but to do it in a new way,” said Sherwood Lollar.

Steinberg’s quantum information science program launched in 2002 and has been renewed three times, most recently this year. The group explores the potential of the growing field of quantum information science, including its applications in disciplines like physics, engineering and computer science.

“What a program like ours needs to do is not just build a computer and solve the problem that FedEx has already ordered, but rather try to demonstrate what determines which of the right problems to use a quantum computer for,” Steinberg said in a video posted on CIFAR’s website.

As for Cowen, her research program coincides with a growing awareness and concern about dangerous fungi, including Candida auris, which was recently covered by the New York Times.

The fungus first appeared in Japan in 2009 and has since spread across the globe, said Cowen.

"It has this amazing ability to survive on surfaces so it's causing outbreaks in hospitals."

Human activity – including global trade, modern medicine and climate change – is intensifying the impact of fungi, according to Cowen. “The fungal kingdom includes as many as six million eukaryotic species and is tremendously diverse in terms of the kind of organisms included and also the impact on global health, agriculture, biodiversity, ecology, manufacturing and even biomedical research.”

Because the implications are so far-reaching, Cowen said there’s a need to bring together researchers from a number of fields who can look at the fungal kingdom from different angles.

“We have brought together these amazing people that are much greater than the sum of the parts,” she said.

Cowen’s program will look at a number of challenges related to fungi, including: the emergence and spread of fungi; how fungi are adapting and interacting with their hosts; what makes some fungi resistant to anti-fungal drugs and fungicide; and developing strategies to thwart fungal diseases.

“It's the first time ever we've brought together this kind of diversity to do a research program to tackle these challenges,” Cowen said.

With a file from Perry King

U of T researcher and global colleagues demonstrate key element of quantum internet

Christopher.Sorensen — Thu, 31 Jan 2019 15:04:32 +0000

U of T researcher and global colleagues demonstrate key element of quantum internet

Christopher.Sorensen Thu, 01/31/2019 - 10:04

Cutline

U of T Professor Hoi-Kwong Lo and his collaborators have performed a proof-of-principle experiment on a key aspect of all-photonic quantum repeaters (photo by Jessica MacInnis)

Jessica MacInnis

Topic

Breaking Research

Faculty of Applied Science & Engineering

Global

Quantum

Arts & Science news staff

A University of Toronto researcher is among a global group of experts who have demonstrated, in principle, a device that could serve as the backbone of a quantum internet.

Hoi-Kwong Lo, a professor in the department of electrical and computer engineering in the Faculty of Applied Science & Engineering, and his collaborators have developed a prototype for a key element of all-photonic quantum repeaters, a critical step in long-distance quantum communication.

“An all-optical network is a promising form of infrastructure for fast and energy-efficient communication that is required for a future quantum internet,” says Lo, who is cross-appointed to the department of physics in the Faculty of Arts & Science.

A quantum internet is considered the Holy Grail of quantum information processing, enabling many novel applications including information-theoretic secure communication. By contrast, today’s internet was not specifically designed for security, and it shows: breaches, break-ins and computer espionage are common challenges. Nefarious hackers are constantly poking holes in sophisticated layers of defence erected by individuals, corporations and governments.

In light of this, researchers have proposed other ways of transmitting data that would leverage key features of quantum physics to provide virtually unbreakable encryption. One of the most promising technologies involves a technique known as quantum key distribution, or QKD. QKD exploits the fact that the simple act of sensing or measuring the state of a quantum system disturbs that system. Because of this, eavesdropping by a third party would leave behind a detectable trace, and the communication could be aborted before sensitive information is lost.

Until now, this type of quantum security has been only demonstrated in small-scale systems. Lo and his team are among a group of global researchers who are laying the groundwork for a future quantum internet by addressing some of the challenges of transmitting quantum information over great distances using optical fibre communication.

Because light signals lose potency as they travel long distances through fibre-optic cables, devices called repeaters are inserted at regular intervals along the line. The repeaters boost and amplify the signals to help transmit the information.

But existing repeaters for quantum information are highly problematic. They require storage of the quantum state at the repeater sites, making the repeaters error prone, difficult to build, and very expensive because they often operate at cryogenic temperatures.

Lo and his team have proposed a different approach. They are working on the development of the next generation of repeaters, called all-photonic quantum repeaters, that would eliminate or reduce many of the shortcomings of standard quantum repeaters. With collaborators at Osaka University, Toyama University and NTT Corporation in Japan, Lo and his team have demonstrated proof-of-concept of their work in a paper recently published in Nature Communications.

“We have developed all-photonic repeaters that allow time-reversed adaptive Bell measurement,” says Lo.

“Because these repeaters are all-optical, they offer advantages that traditional – quantum-memory-based matter – repeaters do not. For example, this method could work at room temperature.”

A quantum Internet could offer applications that are impossible to implement in the conventional Internet, such as impenetrable security and quantum teleportation, which takes advantage of the phenomenon of quantum entanglement to transmit information between atoms separated by large distances.

“Our work helps pave the way toward this future,” Lo says.

The research was funded by the Natural Sciences and Engineering Research Council of Canada, among others.

U of T theoretical astrophysicist among handful of researchers honoured by U.S.-based foundation

Christopher.Sorensen — Mon, 09 Jul 2018 04:00:00 +0000

U of T theoretical astrophysicist among handful of researchers honoured by U.S.-based foundation

Christopher.Sorensen Mon, 07/09/2018 - 00:00

Cutline

Ue-Li Pen, pictured here at the FAST radio telescope in China, is among 16 mathematicians and scientists from across North America and Europe to receive a 2018 Simons Investigators award (photo courtesy of Ue-Li Pen)

Topic

Our Community

Canadian Institute for Theoretical Astrophysics

Dunlap Institute for Astronomy & Astrophysics

Theoretical astrophysicist Ue-Li Pen has been selected by the Simons Foundation to receive a 2018 Simons Investigators award.

Pen, the interim director of the Canadian Institute for Theoretical Astrophysics in the University of Toronto's Faculty of Arts & Science, joins 15 others honoured from across North America and Europe. He is the second researcher at a Canadian institution – and the first from U of T – to be tapped for the award since the program was introduced in 2012.

“Being named a Simons Investigator is a great honour,” said Pen, who is also professor in U of T's department of physics. “I am grateful and humbled to receive this award, which will enable substantial new and innovative astrophysics research opportunities at the University of Toronto.”

Pen is known for developing innovative tools to create new fields of research. His pioneering work on 21 cm intensity mapping opens a new window for the precision study of dark energy and neutrinos.

Recently, his use of natural plasma in our galaxy as a giant telescope spawned the field of scintillometry, enabling new glimpses into enigmatic pulsars and unsolved fast radio bursts. The vastly improved precision may improve our understanding of space-time, including gravitational waves.

The awards are presented by the New York-based Simons Foundation to outstanding scientists in mathematics, physics, astrophysics and theoretical computer science. They support researchers in their most productive years – when they are establishing creative new research directions – providing leadership to the field and effectively mentoring junior scientists.

The award provides $100,000 annually for five years and an additional $10,000 per year is given to the investigator’s department.

Canada gives $12 million to boost power of Large Hadron Collider

noreen.rasbach — Mon, 25 Jun 2018 17:51:06 +0000

Canada gives $12 million to boost power of Large Hadron Collider

noreen.rasbach Mon, 06/25/2018 - 13:51

Cutline

Science Minister Kirsty Duncan announced in Vancouver today that the federal government will give $10 million to the Large Hadron Collider, with TRIUMF giving another $2 million in kind (photo courtesy of Innovation, Science and Economic Development)

Jennifer Robinson

Topic

Global Lens

CERN

Faculty of Applied Science & Engineering

Subheadline

U of T physicists eager to see what secrets the upgraded particle accelerator will reveal next

For more than a decade, a small team of high-energy physicists and graduate students from the University of Toronto have helped push the boundaries of scientific knowledge at the world’s most powerful particle accelerator.

Today, the Canadian government and TRIUMF, Canada’s particle accelerator centre, announced a $12-million investment to give a major performance boost to the Large Hadron Collider, known as the most massive and complex scientific experiment in human history.

The funding will go towards mission critical components in support of the new High-Luminosity Large Hadron Collider (HL-LHC or HiLumi), with Vancouver-based TRIUMF leading production of the Canadian components. HiLumi, which had a groundbreaking ceremony earlier this month, is expected to be operational by 2026.

“I am pleased to announce support for Canada’s outstanding researchers, engineers and technicians, whose combined efforts will further our reputation as a global leader in particle physics,” said federal Science Minister Kirsty Duncan in a news release.

The Large Hadron Collider, a high-energy particle accelerator operated by the European Organization for Nuclear Research (CERN), runs in a 27-kilometre circular tunnel buried 100 metres below the surface of the earth underneath France and Switzerland.

Since opening in 2008, it has enabled scientists to recreate the conditions that existed a billionth of a second after the Big Bang — and to study them in a controlled way. In 2012, researchers announced the discovery of the Higgs boson, the so-called “God particle” that gives other particles mass and makes life possible.

“Researchers at the University of Toronto welcome this important support by the Canadian government to help make one of the world’s most important scientific projects possible,” said Vivek Goel, U of T’s vice-president of research and innovation.

“For more than a decade, U of T researchers have worked side-by-side with colleagues from universities across Canada, at TRIUMF, and around the world to push our knowledge of the fundamental structure of the universe. We look forward to being a part of even more critical breakthroughs as we continue to play a role with the HiLumi project for decades to come.”

One of the areas in which U of T has been involved is the ATLAS detector, one of the main experiments at the Large Hadron Collider.

Right now, the U of T team on ATLAS comprises six faculty, four postdoctoral researchers and 20 graduate students. In the past decade, approximately 50 U of T students have worked at CERN, said U of T physics Professor Robert Orr.

In 2012, the U of T Atlas team (which included Orr and colleagues David Bailey, Peter Krieger, Pierre Savard, Pekka Sinervo, Richard Teuscher and William Trischuk) and their 2,500 ATLAS colleagues from 35 countries played a key role in the hunt for the Higgs boson.

The ATLAS detector, key components of which were built at U of T, was designed to search for new particles in the highest mass collisions of high-energy proton collisions in the Large Hadron Collider.

U of T faculty and graduate students sifted through the massive amounts of data from ATLAS using SciNet super computing resources at U of T to identify collisions containing Higgs boson candidates.

For HiLumi, the Canadian research community will use its world-leading cryomodule technology to build five new particle accelerator components known as crab cavity cryogenic modules, a TRIUMF news release explained.

These sophisticated, ultra low temperature boxes will house crab cavities that “rotate bunches of subatomic particles before they smash together, significantly increasing the number of collisions, or luminosity, of the Large Hadron Collider.”

The souped-up particle accelerator “is very good news — something we’ve been waiting for for quite some time,” said Sinervo. “It will ensure Canada has the official status at CERN that it so appropriately deserves given all the contributions Canadians have made to the experiments and the accelerator.”

The assembly of the crab cavity housing, a cryostat that will serve as a high-performance coldbox, keeping the cavities at their operating temperature (photo by Maximilien Brice/CERN)

The discovery of the Higgs boson was huge, confirming the existence of all the particles making up the Standard Model of particle physics, as well as the existence of the mechanism that gives mass to all the fundamental particles, Orr explained.

Nevertheless, much remains to be discovered and puzzles resolved, such as: Why the pattern of masses? What is dark matter?

“In the context of the Large Hadron Collider, the most important puzzle is the surprisingly small mass of the Higgs,” Orr said.

“Our theoretical understanding leads us to believe this small mass of the Higgs implies there should be a whole zoo of ‘supersymmetric’ particles observable at the LHC. They have not been,” he said.

“It could be that the intensity of the present LHC is insufficient to observe them. That is the main motivation for the HL-LHC — to increase the intensity of the machine to the point where we can observe these new particles.”

On the other hand, Orr said the non-observation of this supersymmetry may also be telling because it “would finally demonstrate that we have to think of some other mechanism that keeps the mass of the Higgs small.

“This could lead to a complete sea change in our understanding of the basic structure of matter.”

With files from Jenny Hall

'Heroic calculation': U of T expert on using new supercomputer to shed light on how oceans behave

noreen.rasbach — Mon, 05 Mar 2018 14:35:12 +0000

'Heroic calculation': U of T expert on using new supercomputer to shed light on how oceans behave

noreen.rasbach Mon, 03/05/2018 - 09:35

Cutline

“This is pure, curiosity-driven research. We hope the results will warrant publication and be a major coup for Niagara,” says U of T's Richard Peltier (photo courtesy of NSERC)

Jennifer Robinson

Topic

Global Lens

Global

To break in Canada’s newest, most powerful research supercomputer, the University of Toronto’s Richard Peltier is running a “heroic calculation” – one that is expected to shed new light on how the world’s oceans physically function.

It’s unknown how long it will take the more than $18-million machine known as Niagara to crunch the millions of gigabytes in real-time data streaming to it now from the ocean bottom of the Pacific.

“It’s never been done before,” said Peltier, a globally renowned climate change expert. “It could be days or even a week depending on the spatial resolution we decide to work at.”

Unveiled today, Niagara is a massive network of 60,000 cores – the equivalent of roughly 60,000 powerful desktop computers – that can be tasked to work together simultaneously on a single, humungous problem.

This type of setup, known as a large parallel system, is the only one in Canada and is housed in a secure, non-descript location in Vaughan, Ont. It’s open to all Canadian university researchers and is part of a national network of research computing infrastructure.

In Geneva, where U of T scientists are on the frontier of physics with world’s largest particle accelerator

geoff.vendeville — Wed, 30 Aug 2017 04:00:00 +0000

In Geneva, where U of T scientists are on the frontier of physics with world’s largest particle accelerator

geoff.vendeville Wed, 08/30/2017 - 00:00

Cutline

CERN, the international lab near Geneva, is home to the Large Hadron Collider, the world’s largest particle accelerator (photo by Claudia Marcelloni/CERN)

Geoffrey Vendeville

Author legacy

Geoffrey Vendeville

Topic

Global Lens