{ "131036-21867622": { "datetime_modified":"20250113T063221", "datetime_start":"20250114T160000", "datetime_end":"20250114T170000", "has_end_time":1, "date_start":"2025-01-14", "date_end":"2025-01-14", "time_start":"16:00:00", "time_end":"17:00:00", "time_zone":"America\/Detroit", "event_title":"CM-AMO Seminar | Double Feature", "occurrence_title":"", "combined_title":"CM-AMO Seminar | Double Feature: Qiuyang Li (U-M Physics) and Dechen Zhang (U-M Physics)", "event_subtitle":"Qiuyang Li (U-M Physics) and Dechen Zhang (U-M Physics)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"Qiuyang Li \r\nU-M Physics\r\n\r\nExcitons and Light-Matter Interaction in Two-Dimensions\r\n\r\nTwo-dimensional (2D) van der Waals (vdW) semiconductors possess unique properties: atomically thin thickness, well-defined exciton state, and strong transition oscillator strength, providing an interesting platform for many-body interactions and optical and electronic applications. In this talk, I will discuss exciton and exciton-polariton properties in two different 2D vdW semiconductors. In the first part, I will report strongly coupled exciton-polaritons of an anisotropic 2D magnet, CrSBr, integrated with an anisotropic photonic crystal (PhC) cavity. In this system, the spin, atomic lattice, and photonic lattices anisotropies are strongly correlated, giving rise to exceptionally strong coupling between engineered anisotropic optical modes and anisotropic excitons in CrSBr and a highly tunable polariton polarization by tens of degrees by many means. In the second part, I will discuss how the twist between two CrSBr monolayers leads to tunable exciton states and anisotropies. Cavity- and twist-tuning on 2D materials provide new opportunities for both fundamental understanding of quantum materials and photonic technology.\r\n\r\n\r\nDechen Zhang\r\nU-M Physics\r\n\r\nField Tunable BKT and Quantum Phase Transitions in Spin-1\/2 Triangular Lattice Antiferromagnet\r\n\r\nQuantum magnetism is one of the most active fields for exploring exotic phases and phase transitions. The recently synthesized Na2BaCo(PO4)2 (NBCP) is an ideal material incarnation of the spin-1\/2 easy axis triangular lattice antiferromagnet (TLAF). Experimental evidence shows that NBCP hosts the spin supersolid state with a giant magnetocaloric effect. It was also proposed that the applied magnetic field B can drive the system through Berezinskii-Kosterlitz-Thouless (BKT) and other richer quantum phase transitions. However, detecting these transitions is a huge challenge because they onset at extremely low-temperature T at around 60 mK, and the measurement of the magnetic susceptibility of these transitions requires high sensitivity. With the help of our newly developed gradient force magnetometer in a dilution refrigerator, we constructed the contour diagram of the magnetic susceptibility in the B-T phase diagram in temperatures as cold as 30 mK. These results provide a more comprehensive and accurate understanding of the several field-tunable quantum phase transitions and BKT melting of the spin supersolidity, which are especially significant when their giant magnetocaloric effects highlight potential applications for sub-Kelvin refrigeration under concerns about global helium shortages.", "occurrence_notes":null, "guid":"131036-21867622@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/131036", "building_id":"1000167", "building_name":"West Hall", "campus_maps_id":"163", "room":"340", "location_name":"West Hall", "has_livestream":0, "cost":"", "tags":["Science","Physics"], "website":"", "sponsors":[ { "group_name":"CM-AMO Seminars", "group_id":"3801", "website":"" }, { "group_name":"Department of Physics", "group_id":"1965", "website":"" } ], "image_url":"", "styled_images":{ "event_thumb":"", "event_large":"", "event_large_2x":"", "event_large_lightbox":"", "group_thumb":"", "group_thumb_square":"", "group_large":"", "group_large_lightbox":"", "event_large_crop":"", "event_list":"", "event_list_2x":"", "event_grid":"", "event_grid_2x":"", "event_feature_large":"", "event_feature_thumb":"" }, "occurrence_count":1, "first_occurrence":21867622 } , "129385-21862604": { "datetime_modified":"20241222T084849", "datetime_start":"20250114T160000", "datetime_end":"20250114T170000", "has_end_time":1, "date_start":"2025-01-14", "date_end":"2025-01-14", "time_start":"16:00:00", "time_end":"17:00:00", "time_zone":"America\/Detroit", "event_title":"Colloquium Seminar: Analysis and Design of High Dimensional Sampling for Scientific Computing", "occurrence_title":"", "combined_title":"Colloquium Seminar: Analysis and Design of High Dimensional Sampling for Scientific Computing: Yifan Chen (Courant Institute, NYU)", "event_subtitle":"Yifan Chen (Courant Institute, NYU)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"Sampling from probability distributions is a fundamental challenge in physics and data science. State-of-the-art methods often rely on building efficient dynamics for probability measures. This talk examines the analysis and design of such dynamics, drawing insights from and targeting applications in high-dimensional scientific computing. \r\n\r\nIn the first part, we uncover and analyze a novel 'delocalization of bias' phenomenon in MCMC with Langevin dynamics. While sampling bias increases with dimensionality in full coordinates, individual coordinates can exhibit nearly dimension-independent behavior. This finding suggests that the curse of dimensionality in sampling may be mitigated at the level of low-dimensional marginals. In the second part, we propose a generative diffusion dynamics design for probabilistic forecasting, focusing on benchmark applications in stochastically forced Navier-Stokes equations. We prove that a specific design of diffusion coefficients minimizes novel statistical errors at the level of path measures and yields F\u00f6llmer processes, which also offer a Bayesian interpretation of the optimal design. We conclude with a real-data scientific application in black hole imaging, where we combine generative diffusion dynamics with MCMC for rigorous posterior sampling. Overall, the talk demonstrates how mathematical understanding and methodological design of high-dimensional sampling dynamics can synergize with insights and applications in scientific computing.", "occurrence_notes":null, "guid":"129385-21862604@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/129385", "building_id":"1000166", "building_name":"East Hall", "campus_maps_id":"53", "room":"1360", "location_name":"East Hall", "has_livestream":0, "cost":"", "tags":["Mathematics"], "website":"", "sponsors":[ { "group_name":"Colloquium Series - Department of Mathematics", "group_id":"4884", "website":"" }, { "group_name":"Department of Mathematics", "group_id":"3791", "website":"" } ], "image_url":"", "styled_images":{ "event_thumb":"", "event_large":"", "event_large_2x":"", "event_large_lightbox":"", "group_thumb":"", "group_thumb_square":"", "group_large":"", "group_large_lightbox":"", "event_large_crop":"", "event_list":"", "event_list_2x":"", "event_grid":"", "event_grid_2x":"", "event_feature_large":"", "event_feature_thumb":"" }, "occurrence_count":1, "first_occurrence":21862604 } , "130486-21866105": { "datetime_modified":"20250106T151154", "datetime_start":"20250114T160000", "datetime_end":"20250114T180000", "has_end_time":1, "date_start":"2025-01-14", "date_end":"2025-01-14", "time_start":"16:00:00", "time_end":"18:00:00", "time_zone":"America\/Detroit", "event_title":"DAAS Africa Workshop", "occurrence_title":"", "combined_title":"DAAS Africa Workshop: Waiting for Valdez with Teddy Mattera, South African Filmmaker", "event_subtitle":"Waiting for Valdez with Teddy Mattera, South African Filmmaker", "event_type":"Film Screening", "event_type_id":"11", "description":"Please join us for a special screening of \"Waiting for Valdez\" a film by South African filmmaker Teddy Mattera. \r\nWaiting for Valdez\" tells the story of a young boy named Sharky living in apartheid-era Johannesburg, who is desperately trying to see the movie \"Valdez is Coming\" starring Burt Lancaster, but due to his circumstances under segregation, he can only experience the film through secondhand accounts from friends, ultimately missing the conclusion due to his grandmother's illness, providing a poignant portrait of the everyday life under the oppressive regime; the film uses the \"Valdez is Coming\" narrative as a symbol of hope and resistance against injustice.\r\nMattera will be present via zoom to discuss the film following the screening.", "occurrence_notes":"https:\/\/umich.zoom.us\/j\/96450047609", "guid":"130486-21866105@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/130486", "building_id":"1000175", "building_name":"Haven Hall", "campus_maps_id":"542", "room":"4701 Haven Hall (DAAS Conference Room)", "location_name":"Haven Hall", "has_livestream":0, "cost":"", "tags":["African Studies Center","africa","african diaspora","African Studies","South Africa","film screening","film","daas"], "website":"", "sponsors":[ { "group_name":"Department of Afroamerican and African Studies", "group_id":"1144", "website":"http:\/\/www.lsa.umich.edu\/daas\/" }, { "group_name":"African Studies Center", "group_id":"3187", "website":"http:\/\/www.ii.umich.edu\/asc\/" } ], "image_url":"https:\/\/events.umich.edu\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "styled_images":{ "event_thumb":"https:\/\/events.umich.edu\/media\/cache\/event_thumb\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_large":"https:\/\/events.umich.edu\/media\/cache\/event_large\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_large_2x":"https:\/\/events.umich.edu\/media\/cache\/event_large_2x\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/event_large_lightbox\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "group_thumb":"https:\/\/events.umich.edu\/media\/cache\/resolve\/group_thumb\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "group_thumb_square":"https:\/\/events.umich.edu\/media\/cache\/resolve\/group_thumb_square\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "group_large":"https:\/\/events.umich.edu\/media\/cache\/resolve\/group_large\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "group_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/resolve\/group_large_lightbox\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_large_crop":"https:\/\/events.umich.edu\/media\/cache\/resolve\/event_large_crop\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_list":"https:\/\/events.umich.edu\/media\/cache\/resolve\/event_list\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_list_2x":"https:\/\/events.umich.edu\/media\/cache\/event_list_2x\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_grid":"https:\/\/events.umich.edu\/media\/cache\/event_grid\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_grid_2x":"https:\/\/events.umich.edu\/media\/cache\/resolve\/event_grid_2x\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_feature_large":"https:\/\/events.umich.edu\/media\/cache\/resolve\/event_feature_large\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg", "event_feature_thumb":"https:\/\/events.umich.edu\/media\/cache\/resolve\/event_feature_thumb\/media\/attachments\/2025\/01\/event_130486_original-1.jpeg" }, "occurrence_count":1, "first_occurrence":21866105 } }