Department of Physics, University of Toronto

Department of Physics, University of Toronto The Department of Physics is spread over 3 campuses: St. George Campus (Downtown), Scarborough campu

Colloquium: Big Boxes, Not Black Boxes: What we can compute about LLMsZohar Ringel, The Hebrew University of JerusalemDe...
09/28/2026

Colloquium: Big Boxes, Not Black Boxes: What we can compute about LLMs

Zohar Ringel, The Hebrew University of Jerusalem

Deep networks are often thought of as black boxes. Their ability to encompass vast swathes of knowledge indeed makes them hard to explain. Yet many of their behaviours — generalization under over-parametrization, grokking, OOD failures, neural scaling laws — recur across architectures and scales, and each, however surprising, can be reproduced and explained in controlled settings. I will review these efforts to identify and explain the universal phenomena of deep learning, and suggest that an LLM may amount to a sum of such tractable sub-phenomena, interpolative in nature. Finally, I'll suggest that what separates this prosaic picture from the apparent magic of LLMs may well be the industrial scale of compute and human labour behind it.

Thursday, October 1, 2026
3:10 p.m. EST
Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

The presentation will also be streamed on Zoom where you can view it on your own device.

To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

Colloquium: The First Flight of the GAPS Dark Matter Experiment: Dispatches from AntarcticaField Rogers, University of C...
09/21/2026

Colloquium: The First Flight of the GAPS Dark Matter Experiment: Dispatches from Antarctica

Field Rogers, University of California, Berkeley

The fundamental nature of dark matter is a central mystery of physics in the 21st century. Particle interactions of the dark matter in our Galaxy could contribute characteristic signatures to the charged cosmic-ray, neutrino, and multiwavelength sky. For astrophysical searches seeking these signatures, the central challenge lies in distinguishing possible dark matter signals from backgrounds associated with other astrophysical processes. Within this high-background context, low-energy cosmic-ray antideuterons are unique. The dark matter prediction exceeds the expected background by two orders of magnitude, so any detection would be an unambiguous signal of new physics.

The balloon-borne General Antiparticle Spectrometer (GAPS) is the first experiment optimized for low-energy cosmic-ray antideuterons. GAPS will also measure the cosmic-ray antiproton spectrum in an unexplored energy range and provide new sensitivity to cosmic-ray antihelium nuclei. After more than two decades of development, integration, testing, and calibration on the ground, the first of several planned GAPS science payloads took to the stratosphere on 16 December, 2025 and flew for 25 days above the continent of Antarctica. I will introduce the GAPS instrument and its unique detection strategy, share tales from balloon campaign, and present the data from the first flight.

Thursday, September 24, 2026
3:10 p.m. EST
Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

Colloquium: On achieving realism in quantum theoryRobert Spekkens, Perimeter Institute for Theoretical PhysicsCan we hav...
09/15/2026

Colloquium: On achieving realism in quantum theory

Robert Spekkens, Perimeter Institute for Theoretical Physics

Can we have a satisfactory realist interpretation of quantum theory, and what principles should guide our search for one? I will advocate a middle road between operationalism and unconstrained realism, guided by a methodological principle inspired by Leibniz: scenarios that are empirically indistinguishable in principle should be represented as physically identical. This principle played a pivotal role in Einstein’s development of relativity. What follows if we take it equally seriously in quantum theory? Within the conventional framework for realism, it leads to constraints that conflict with quantum predictions, as witnessed by no-go results such as Bell’s theorem and the Kochen–Specker theorem. If we are to retain the Leibnizian principle, therefore, we must move beyond this framework to a more expansive conception of realism. I propose that the central commitment of a realist should be securing causal accounts of statistical correlations, and that quantum theory calls for a revision of our notions of causation and inference, much as relativity called for a revision of our notions of space and time. A central task of this research programme is to distinguish between the parts of the quantum formalism that describe how physical systems influence one another and those that describe what we can infer about one system by learning about another. I will conclude by outlining recent work towards “unscrambling the quantum omelet.”

Thursday, September 17, 2026
3:10 p.m. EST
Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

The presentation will also be streamed on Zoom where you can view it on your own device.

To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

Colloquium: Time’s Second Arrow: Evolution, Order, and a New Law of NatureRobert Hazen, Carnegie ScienceA pervasive wond...
03/30/2026

Colloquium: Time’s Second Arrow: Evolution, Order, and a New Law of Nature

Robert Hazen, Carnegie Science

A pervasive wonder of the natural world is the evolution of varied systems, including stars, planets, minerals, and life—all of which have increased in diversity and patterning over deep time. However, no law of nature describes and explains, much less quantifies and predicts, the behavior of complex evolving systems. Accordingly, our group has proposed a new law of nature, the “law of increasing functional information,” that we apply to the evolution of both abiotic systems (isotopes, minerals) and life. This postulated increase in functional information represents a second arrow of time—one that is consistent with the increase in entropy (the first arrow of time) but is not derivable from the laws of thermodynamics. This concept is now being applied and tested by other groups in fields as wide-ranging as the evolution of languages, the behavior of AI systems, the seasonal variations of soil microbiomes, and the search for new cancer therapies. Mineral evolution, which explores the diversification of Earth’s mineral kingdom on more than 4.5 billion years, is an especially revealing test case of this proposed law of nature.

Thursday, April 2, 2026
3:10 p.m. EST
Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

MathMatize: a useful tool for making better formative assessments in physics coursesBrian Wilson, UofT PhysicsThursday, ...
03/23/2026

MathMatize: a useful tool for making better formative assessments in physics courses

Brian Wilson, UofT Physics

Thursday, March 26, 2026
3:10 p.m. EST, Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

Formative assessments are supposed to provide students with crucial feedback about their learning and progress in a course. Ideal formative assessments are low-pressure, challenging tasks which are graded and returned quickly. Unfortunately, large class sizes make it difficult to provide timely feedback via traditional homework assignments.

In this colloquium I will describe my use of the MathMatize app in the context of a large, second-year electricity and magnetism course to create more meaningful formative assessments. Similarly to other common in-class response tools (clickers, Learning Catalytics or Top Hat), it can be used to create simple multiple-choice or fill-a-blank questions. It's most powerful feature, however, is an ability to fully understand mathematical equivalence, allowing implementation of formulae. This allows for practising symbolic notations on various levels, helping students develop formal mathematical competencies required in upper-level courses.

If you bring an electronic device with internet access and a browser, there will be sample questions to try out for yourself!

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

The presentation will also be streamed on Zoom where you can view it on your own device.

To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

THIS EVENT IS NOW CANCELLED!!!Colloquium: When the planet becomes the dataset: A paradigm shift in illuminating Earth’s ...
03/16/2026

THIS EVENT IS NOW CANCELLED!!!
Colloquium: When the planet becomes the dataset: A paradigm shift in illuminating Earth’s dynamic interior
Presenter: Edward Garnero, Arizona State University

Thursday, March 19, 2026
3:10 p.m. EST
Room 102
McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario

For decades, the growth of freely available seismic data has led to key discoveries about earthquakes and Earth’s properties. From crust to inner core, seismologists have sharpened the focus on key structures that enable inference on Earth’s internal dynamics, composition, and evolution. This presentation will address the continued increase in availability of data, the challenges to find, collect, and store them, and our efforts to collect every relevant seismogram on Earth, for improved Earth imaging.

Why care? While seismic imaging reveals Earth interior phenomena at the best possible resolution, most structures lack enough constraints to definitively understand their nature and origin. This includes massive lower mantle continental-sized Large Low Velocity Provinces (LLVPs), which are situated away from subduction (places where tectonic plates fall into the interior) and generally underly hot spot volcanoes. Sometimes over 1000 km thick, seismic evidence suggests LLVPs are compositionally different from the surrounding mantle. But what are they? And how well are they really imaged? At smaller scales Ultra-Low Velocity Zones (ULVZs) are thin (10’s of km) structures right at the CMB, probably partially molten and possibly also compositionally distinct. How do these structures relate to Earth’s formation, evolution, and mantle dynamics? What are they made of? How well are we seeing them? These questions and others require seismic analyses with the best and most abundant data possible. They require multidisciplinary approaches with mineral physicists, geodynamicists, geochemists, tectonicists, and others.

But how can we sharpen the focus? In this presentation I will highlight our inherent spatial and temporal biases in seismic imaging of these and other structures, where uneven sampling of Earth figures prominently in the challenges. To mitigate these, I’ll present our ongoing effort to bring big data to the table, with a focus on using every available seismogram, combined with measurements of unutilized seismic reverberations that sometimes echo and reflect their way around the entire planet. I’ll briefly mention the potential for machine learning and AI to uncover subtle waveform phenomena. Earth’s resonances and reverberations hold profound potential for advancing our understanding of planetary formation and evolution.

Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

The presentation will also be streamed on Zoom where you can view it on your own device.

To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

Colloquium: A decade of black hole observations with gravitational wavesKaterina Chatziioannou, California Institute of ...
03/09/2026

Colloquium: A decade of black hole observations with gravitational waves
Katerina Chatziioannou, California Institute of Technology

Thursday, March 12, 2026
3:10 p.m. EST, Room 102
McLennan Physical Laboratories, 60 St. George Street, Toronto, Ontario

In just ten years, gravitational-wave astrophysics has progressed from a young, promising field to one with an observational yield of hundreds of signals. Spearheaded by the twin LIGO detectors, the most sensitive detectors to date, observations of merging black holes have revealed a diverse population of stellar-mass objects. These discoveries have reshaped our understanding of black hole demographics and have enabled unprecedented tests of gravity in the strong-field, highly dynamical regime. In this talk, I will briefly review key results on black holes obtained from hundreds of gravitational-wave detections. I will then focus on GW250114, the “decadal” signal of gravitational-wave astronomy that showcases the promise of the upgraded LIGO detectors for probing the fundamental nature of black holes and gravity. GW250114’s exceptionally high signal-to-noise ratio enabled the direct observation of multiple quasinormal modes in the ringdown of the remnant black hole. This landmark measurement allowed us to test the no-hair theorem, which links the mode frequencies to the Kerr spectrum, as well as Hawking’s black hole area law, which states that the total horizon area of black holes cannot decrease.


Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

The presentation will also be streamed on Zoom where you can view it on your own device.
To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

Lessons from smart slimeKaren Alim, Technical University of MunichThursday, March 5, 2026, 3:10 p.m. ESTRoom 102, McLenn...
03/02/2026

Lessons from smart slime
Karen Alim, Technical University of Munich
Thursday, March 5, 2026, 3:10 p.m. EST

Room 102, McLennan Physical Laboratories
60 St. George Street, Toronto, Ontario
Coffee and cookies will be served in the Physics Lounge at 2:45 p.m.
https://www.physics.utoronto.ca/news-and-events/events/colloquium/

Propagating, storing and processing information is key to take smart decisions – for organisms as well as for autonomous devices. In search for the minimal units that allow for complex behaviour, the slime mould Physarum polycephalum stands out by solving complex optimization problems despite its simple make-up. Physarum’s body is an interlaced network of fluid-filled tubes lacking any nervous system, in fact being a single gigantic cell. Yet, Physarum finds the shortest path through a maze. We unravel that Physarum’s complex behaviour emerges from the physics of active flows shuffling through its tubular networks. Flows transport information, information that is stored in the architecture and mechanical state of the network. Thus, tubular adaptation drives processing of information into complex behaviour. Taking inspiration from the mechanisms in Physarum we outline how to embed complex behaviour in active microfluidic devices and how to program human vasculature.

The presentation will also be streamed on Zoom where you can view it on your own device.
To join via Zoom, please use this link:
https://us06web.zoom.us/j/84634223695?pwd=R29qMlF3OFA2QVY0S1N5Q2R5Z1JyUT09
Webinar ID: 84634223695
Passcode: 122753

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