Ordinary materials are "passive" in the sense that their constituents are typically made by inert particles which are subjected to thermal fluctuations, internal interactions and external fields but do not move on their own. Living systems, like schools of fish, swarms of birds, pedestrians and swimming microbes are called "active matter" since they are composed of self-propelled particles. Active matter is intrinsically in nonequilibrium and exhibits a plethora of novel phenomena as revealed by a recent combined effort of statistical theory, computer simulation and real-space experiments. After an introduction on biological and artificial self-propelled particles [1], the talk will focus on modelling of active Brownian particles and collective phenomena like motility-induced phase separation. Finally effects of inertia and the formation of active complexes will be discussed including an inertial delay [2], the coexistence of two states with different temperatures [3], an active refrigerator [4] and entropons in active crystals [5].[1] For a review, see: C. Bechinger, R. di Leonardo, H. Löwen, C. Reichhardt, G. Volpe, G. Volpe,Active particles in complex and crowded environments, Reviews of Modern Physics 88, 045006 (2016).[2] C. Scholz, S. Jahanshahi, A. Ldov, H. Löwen, Inertial delay of self-propelled particles, Nature Communications 9, 5156 (1-9) (2018).[3] S. Mandal, B. Liebchen, H. Löwen, Motility-induced temperature differences in coexisting phases, Phys. Rev. Letters 123, 228001 (2019).[4] L. Hecht, S. Mandal, H. Löwen, B. Liebchen, Active refrigerators powered by inertia, Phys. Rev. Letters 129, 178001 (2022).[5] L. Caprini, U. M. B. Marconi, A. Puglisi, H. Löwen, Entropons as collective excitations in active solids, J. Chem. Phys. 159, 041102 (2023).
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.
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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.
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.
Music has long filled a uniquely important role in bridging human culture and biology, stretching back over millennia, and of course today provides respite and remedy in an increasingly stressful world. We do not sing alone. On land, four kinds of animals produce songs or calls: birds, frogs, mammals, and insects. Some of these animals (and fish) also do so underwater. The principal sounds such animal species make are signaling behaviors directly related to mating success and social cohesion and their ranges are molded by their forms and by their particular forest, savannah or seaside habitat.Human music also has origins, motivations and mechanisms in common with other animals. Traces of a long and ongoing history comes from archaeology, anthropology and brain studies. Evidence of a measurable impact on human biology comes from neurobiology, social psychology, and public health.
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.
Gravitational waves (GWs) are probes of the cosmological model since, as electromagnetic waves, they travel across the largest distances in our Universe. These signals can also track generic modifications of General Relativity on large scales, especially when combined with other cosmological probes. There are several methods for using such fascinating signals to learn more about cosmology. For instance, GWs are distance indicators, and similarly to supernovae, they allow reconstructions of a distance-redshift relation when the latter can be inferred from electromagnetic counterparts emitted by the same source or known indirectly via binary population studies or galaxy catalogs. In this colloquium I will discuss some of the current methods for doing cosmological parameter estimation and tests of gravity with GWs, focusing on studies of future multi-messenger observations and on combinations of GW data with large-scale structure surveys.
