Physics

In this colloquium, the communicative boundary between science and society in Africa will be explored, using physics as an illustration. Different types of contact zones and scenes will be discussed, as well as the societal impact of staging and narrative formats. Based on our ongoing engagement project Making Science the Star, an overview of the relationship between sender and receiver will be presented, and recipes for tuning this interaction to unlock untapped potential in predominantly non-scientific communities will be analyzed.

DISCLAIMER: This talk contains Season1 Episode2 from the show series Science In The City. This is used with permission from Dr. Stéphane Kenmoe, Producer of the series and Presenter of this talk.

---

Bio: Stéphane Kenmoe got a Ph.D. in Physics from the Max Planck Institute for Iron Research in Germany in 2015. He is presently a habilitation candidate at the Faculty of Chemistry at the University of Duisburg-Essen, Germany. He is also a science popularizer on TV and on social media, a science writer and a novelist. In 2020, he produced the movie ‘’Science in the City’’ (Science dans la Cité) in Cameroon. He is very active in networking for the promotion of early career African scientists and for connecting science and society. He has won many awards for his engagement, among which the 2020 Diversity Prize for Academic Leadership at the University of Duisburg-Essen, the Falling Walls Award for Science Engagement in 2021 and the Award for Prototypes of Humanity of the Dubai Authority for arts and culture in 2022. Since 2022, he is the chief editor of the African Physics Newsletter, an electronic quarterly about physics in Africa published by the American Physical Society. 

---

Zoom link: https://pitp.zoom.us/j/92725978684?pwd=Yys0ci9JdE0zS054SGxyaWoxZkdUUT09

During this colloquium, I will discuss my journey in looking for astronomical information hiding in the ancestral knowledge of my community. I will show concrete examples of my findings and encourage communities to engage in similar practice to provide content that could be used to teach indigenous Astronomy in classrooms. 

---

Bio:

Laurie Rousseau-Nepton is a new faculty at the University of Toronto and the Dunlap Institute for Astronomy and Astrophysics. She comes with six years of experience working as a resident astronomer at the Canada-France-Hawaii Observatory supporting various instruments including wide-field cameras, high-resolution spectrographs, Fourier Transform Spectro-imager. She received her diploma from Université Laval by studying regions of star formation in spiral galaxies and helping with the development of two Fourier Transform Spectro-imagers, SpIOMM and SITELLE. She is now leading an international project called SIGNALS, the Star formation,Ionized Gas, and Nebular Abundances Legacy Survey, which sampled with the SITELLE instrument more than 50,000 of star-forming regions in 40 nearby galaxies to understand how the local environment affect the young star clusters characteristics.

This seminar will be divided in two segments: 1) New Instrumentation for Astronomy and 2) the SIGNAL-Survey of Star-forming regions in Nearby Galaxy.

1) Evolution of technologies and optics manufacturing technics are providing new interesting options for the design of astronomical instruments to increase precision and add new capabilities. In this presentation, I will discuss my new laboratory plan at the University of Toronto to include Micro-kinetic inductance detector arrays and meta-surface optics to a Fourier Transform Imaging spectrograph design. The goal is to reach high-spectral resolution (R:15,000 to 80,000) over a large field-of-view, while keeping high sensitivity.

2) SIGNALS stands for the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey. Using a Fourier Transform Imaging Spectrograph SITELLE, at the Canada-France-Hawaii Telescope, we observed 40 nearby galaxies and covered over 50,000 star-forming regions in different environment at a spatial resolution from 0.5 to 40 pc. Covering several emission line spectral features including Halpha (at R: 5,000), the survey aims at characterizing the star-forming sites and their environments to produce the most complete and well resolved database on star formation.

---

Zoom link https://pitp.zoom.us/j/94273599584?pwd=TUY3UFpVa20wbkJUcEdoTmlYUzlQUT09

---

Bio:

Laurie Rousseau-Nepton is a new faculty at the University of Toronto and the Dunlap Institute for Astronomy and Astrophysics. She comes with six years of experience working as a resident astronomer at the Canada-France-Hawaii Observatory supporting various instruments including wide-field cameras, high-resolution spectrographs, Fourier Transform Spectro-imager. She received her diploma from Université Laval by studying regions of star formation in spiral galaxies and helping with the development of two Fourier Transform Spectro-imagers, SpIOMM and SITELLE. She is now leading an international project called SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, which sampled with the SITELLE instrument more than 50,000 of star-forming regions in 40 nearby galaxies to understand how the local environment affect the young star clusters characteristics. 

With rapid progress in simulation of strongly interacting quantum Hamiltonians, the challenge in characterizing unknown phases becomes a bottleneck for scientific progress. We demonstrate that a Quantum-Classical hybrid approach (QuCl) of mining the projective snapshots with interpretable classical machine learning, can unveil new signatures of seemingly featureless quantum states. The Kitaev-Heisenberg model on a honeycomb lattice with bond-dependent frustrated interactions presents an ideal system to test QuCl. The model hosts a wealth of quantum spin liquid states: gapped and gapless Z2 spin liquids, and a chiral spin liquid (CSL) phase in a small external magnetic field. Recently, various simulations have found a new intermediate gapless phase (IGP), sandwiched between the CSL and a partially polarized phase, launching a debate over its elusive nature. We reveal signatures of phases in the model by contrasting two phases pairwise using an interpretable neural network, the correlator convolutional neural network (CCNN). We train the CCNN with a labeled collection of sampled projective measurements and reveal signatures of each phase through regularization path analysis. We show that QuCl reproduces known features of established spin liquid phases and ordered phases. Most significantly, we identify a signature motif of the field-induced IGP in the spin channel perpendicular to the field direction, which we interpret as a signature of Friedel oscillations of gapless spinons forming a Fermi surface. Our predictions can guide future experimental searches for U(1) spin liquids.

--

Zoom link: https://pitp.zoom.us/j/94233944575?pwd=OVljLzMrZzlKeUErNHZQRkEzMFRKUT09

The aim of the Hammers & Nails climate workshop was to give researchers at Perimeter a unique opportunity to interact with invited experts from diverse fields related to climate, energy and biodiversity. The first half of the workshop was dedicated to short research pitches, where both PI researchers as well as invited guests from the Math4Climate network (including e.g. Waterloo Center for Innovation and Complexity, UW's Climate Institute, Energy Institute, Water Institute) could present their hammers & nails. Nails refers to open challenges within climate, energy & biodiversity research. Hammers refers to methods used by PI researchers in their daily work (e.g. causal inference, techniques in algebraic topology, strong gravity simulations etc.). The second half of the workshop built on these pitches through informal group discussions. Conversations from the workshop may be continued in the future through informal lunches and reading groups.

The aim of the Hammers & Nails climate workshop was to give researchers at Perimeter a unique opportunity to interact with invited experts from diverse fields related to climate, energy and biodiversity. The first half of the workshop was dedicated to short research pitches, where both PI researchers as well as invited guests from the Math4Climate network (including e.g. Waterloo Center for Innovation and Complexity, UW's Climate Institute, Energy Institute, Water Institute) could present their hammers & nails. Nails refers to open challenges within climate, energy & biodiversity research. Hammers refers to methods used by PI researchers in their daily work (e.g. causal inference, techniques in algebraic topology, strong gravity simulations etc.). The second half of the workshop built on these pitches through informal group discussions. Conversations from the workshop may be continued in the future through informal lunches and reading groups.

Complementing the spectacular breakthroughs in gravitational wave and multi-messenger astronomy, advancements in our theoretical understanding and modelling of the strong gravity are essential to apprehending the nonlinear dynamics of spacetime, and to unlocking the full potential of the observations. I will illustrate the scope of new physics that might be probed by black holes, neutron stars, and other such systems, including testing general relativity and strong gravity signatures of new particles, and describe some recent developments that allow for uncovering novel phenomena and making detailed predictions in this regime.

Zoom Link: https://pitp.zoom.us/j/96180256322?pwd=LzEyd3ZBWGdZeDR6MjB1dGpLWFRpUT09

There are fascinating new insights we could achieve if we succeeded in connecting quantum gravity to particle physics in the visible and the dark universe. However, making such a connection is challenging, because the typical scale of quantum gravity is believed to be far from the typical scales in particle physics. I will exploit lever arms that could make it possible to bridge this gap in scales.  To provide concrete examples for these ideas, I will review recent results on the proton lifetime in quantum gravity, the effects of asymptotically safe quantum gravity on properties of Standard Model matter and the effects of asymptotically safe quantum gravity on simple models of dark energy and dark matter.

Zoom Link: https://pitp.zoom.us/j/96545839038?pwd=UG1IVzJPWUZGa2ovOFhzdHBhOFhOdz09

Tensor Processing Units are application specific integrated circuits (ASICs) built by Google to run large-scale machine learning (ML) workloads (e.g. AlphaFold). They excel at matrix multiplications, and hence can be repurposed for applications beyond ML. In this talk I will explain how TPUs can be leveraged to run large-scale density matrix renormalization group (DMRG) calculations at unprecedented size and accuracy. DMRG is a powerful tensor network algorithm originally applied to computing ground-states and low-lying excited states of strongly correlated, low-dimensional quantum systems. For certain systems, like one-dimensional gapped or quantum critical Hamiltonians, or small, strongly correlated molecules, it has today become the gold standard method for computing e.g. ground-state properties. Using a TPUv3-pod, we ran large-scale DMRG simulations for a system of 100 spinless fermions, and optimized matrix product state wave functions with a bond dimension of more than 65000 (a parameter space with more than 600 billion parameters). Our results clearly indicate that hardware accelerator platforms like Google's latest TPU versions or NVIDIAs DGX systems are ideally suited to scale tensor network algorithms to sizes that are beyond capabilities of traditional HPC architectures.

Zoom link:  https://pitp.zoom.us/j/99337818378?pwd=SGZvdFFValJQaDNMQ0U1YnJ6NU1FQT09

Schrodinger's thought experiment famously illustrates the dramatic effect of measuring a quantum state. The resulting wave function collapse is often thought to make states more classical and familiar. However, in this colloquium, we explore how measurements can be used as a chisel to efficiently build exotic forms of quantum entanglement. We focus on topological states of matter, whose quasiparticles exhibit generalized 'anyonic' exchange statistics with potential relevance to quantum computation. We use these ideas to experimentally realize the first controlled realization of non-Abelian anyons, which can remember the sequence in which they are exchanged. The smoking gun signature of this experiment is inspired by the coat of arms of the House of Borromeo.

Zoom Link: https://pitp.zoom.us/j/98167813390?pwd=aG5vcklVZzBWT1BRSjI4RVRtbDhBUT09

We explore how measurements and unitary feedback can generate distinct phases of matter from a given resource state, with a specific focus on the toric code in two dimensions. First, we map random Pauli measurements on the toric code to a classical loop model with crossings, and we show how measurement-induced entanglement exactly maps to watermelon correlators of the loop model.  Then, we consider measuring all but a 1d boundary of qubits, and we map this setup to hybrid circuits in 1+1 dimensions.  In particular, we find that varying the probabilities of different Pauli measurements can drive phase transitions in the unmeasured boundary between phases with different orders and entanglement scaling, corresponding to short and long loop phases in the classical model.  Finally, by utilizing single-site boundary unitaries conditioned on the bulk measurement outcomes, we generate mixed state ordered phases and transitions that can be experimentally diagnosed with linear observables. Our findings showcase the potential of measurement-based quantum computing setups in producing and manipulating phases of matter.

Zoom Link: https://pitp.zoom.us/j/99159680593?pwd=V29wRit6T3NlSjZGTDEvTnRFcTlrUT09

The classical spacetime manifold of general relativity disappears in quantum gravity, with different research programs suggesting a variety of alternatives in its place. As an illustration of how philosophers might contribute to an interdisciplinary project in quantum gravity, I will give an overview of recent philosophical debates regarding how classical spacetime "emerges."  I will criticize some philosophers as granting too much weight to the intuition that a coherent physical theory must describe objects as located in space and time.  I will further argue, based in part on historical episodes, that an account of emergence needs to recover the structural features of classical GR responsible for its empirical success.  This is more demanding than it might at first appear, although the details of recovery will differ significantly among different approaches to quantum gravity.

Zoom link:  https://pitp.zoom.us/j/98331676824?pwd=VTNOakMxWWUzT2ZFZFYwYzBRdWxBUT09