{ "149342-21906254": { "datetime_modified":"20260908T142951", "datetime_start":"20260918T150000", "datetime_end":"20260918T160000", "has_end_time":1, "date_start":"2026-09-18", "date_end":"2026-09-18", "time_start":"15:00:00", "time_end":"16:00:00", "time_zone":"America\/Detroit", "event_title":"Extremal set theory as algebraic geometry", "occurrence_title":"", "combined_title":"Extremal set theory as algebraic geometry: Russ Woodroofe (University of Primorska)", "event_subtitle":"Russ Woodroofe (University of Primorska)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"Extremal set theory asks questions such as \"what is the largest family of pairwise intersecting k-element subsets of an n-element set?\" Many questions of this type can be modeled with exterior algebras, and admit extensions such as \"what is the largest self-annihilating subspace of k-forms in an n-variable exterior algebra?\" The shifting technique in extremal set theory corresponds to algebraic geometric limits of certain curves in a Grassmannian.\n\nIn this talk, I will overview these connections, and go on to discuss recent joint work with Bulavka and Gandini. We find a maximum subspace of k-forms in an n-variable exterior algebra that is self-annihilating but not annihilated by any 1-form. A difficulty is that \"not annihilated by any 1-form\" is not a closed condition in the Grassmannian. This work extends the Hilton-Milner theorem of extremal set theory to the exterior algebra setting, and answers questions of Scott and Wilmer and of my own.", "occurrence_notes":null, "guid":"149342-21906254@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/149342", "building_id":"1000166", "building_name":"East Hall", "campus_maps_id":"53", "room":"4088", "location_name":"East Hall", "has_livestream":0, "cost":"", "tags":["Mathematics"], "website":"", "sponsors":[ { "group_name":"Combinatorics Seminar - Department of Mathematics", "group_id":"4885", "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":21906254 } , "149752-21907056": { "datetime_modified":"20260910T095305", "datetime_start":"20260925T150000", "datetime_end":"20260925T160000", "has_end_time":1, "date_start":"2026-09-25", "date_end":"2026-09-25", "time_start":"15:00:00", "time_end":"16:00:00", "time_zone":"America\/Detroit", "event_title":"A tale of two polynomials: positivity in wonderful varieties and matroids", "occurrence_title":"", "combined_title":"A tale of two polynomials: positivity in wonderful varieties and matroids: Shiyue Li (University of Michigan)", "event_subtitle":"Shiyue Li (University of Michigan)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"I will share a story of two polynomials, the Poincar\u00e8 polynomial of Chow rings of toric varieties of matroids, and the h-polynomials of nested set complexes of matroids. The story is set in a rich network of positivity properties coming from geometry and combinatorics of matroids, with connections to moduli spaces of rational stable curves. The main theorems are matroidal analogues of Gal\u2019s conjecture, and real-rootedness of some of these polynomials. (Joint works with Basile Coron, and Luis Ferroni)", "occurrence_notes":null, "guid":"149752-21907056@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/149752", "building_id":"1000166", "building_name":"East Hall", "campus_maps_id":"53", "room":"4088", "location_name":"East Hall", "has_livestream":0, "cost":"", "tags":["Mathematics"], "website":"", "sponsors":[ { "group_name":"Combinatorics Seminar - Department of Mathematics", "group_id":"4885", "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":21907056 } , "149734-21907011": { "datetime_modified":"20260731T230300", "datetime_start":"20261002T150000", "datetime_end":"20261002T160000", "has_end_time":1, "date_start":"2026-10-02", "date_end":"2026-10-02", "time_start":"15:00:00", "time_end":"16:00:00", "time_zone":"America\/Detroit", "event_title":"Combinatorics Seminar", "occurrence_title":"", "combined_title":"Combinatorics Seminar: Christian Gaetz (UC Berkeley)", "event_subtitle":"Christian Gaetz (UC Berkeley)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"TBD", "occurrence_notes":null, "guid":"149734-21907011@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/149734", "building_id":"1000166", "building_name":"East Hall", "campus_maps_id":"53", "room":"4088", "location_name":"East Hall", "has_livestream":0, "cost":"", "tags":["Mathematics"], "website":"", "sponsors":[ { "group_name":"Combinatorics Seminar - 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