{ "151698-21911991": { "datetime_modified":"20261012T130002", "datetime_start":"20261116T160000", "datetime_end":"20261116T170000", "has_end_time":1, "date_start":"2026-11-16", "date_end":"2026-11-16", "time_start":"16:00:00", "time_end":"17:00:00", "time_zone":"America\/Detroit", "event_title":"GLNT: Arithmetic intersections on non-split Cartan modular curves", "occurrence_title":"", "combined_title":"GLNT: Arithmetic intersections on non-split Cartan modular curves: Jonathan Love (UM)", "event_subtitle":"Jonathan Love (UM)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"Abstract: Take two CM elliptic curves over a number field, each equipped with a level structure preserved by all endomorphisms. At which primes $p$ does there exist an isomorphism between the elliptic curves mod $p$ that preserves the level structures? This question was answered for $\\Gamma_0(N)$ level structure by Gross, Kohnen, and Zagier in 1987. A key step in their proof is showing that an isomorphism mod $p$ determines embeddings of the (quadratic) CM orders into a common (quaternion) Eichler order. In this talk, we will discuss what changes in the argument when we replace $\\Gamma_0(N)$ with the normalizer of a non-split Cartan subgroup. This is joint work with Elie Studnia and Jan Vonk.", "occurrence_notes":null, "guid":"151698-21911991@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/151698", "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":"Group, Lie and Number Theory Seminar - Department of Mathematics", "group_id":"4892", "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":21911991 } , "153898-21916610": { "datetime_modified":"20261021T070353", "datetime_start":"20261123T160000", "datetime_end":"20261123T170000", "has_end_time":1, "date_start":"2026-11-23", "date_end":"2026-11-23", "time_start":"16:00:00", "time_end":"17:00:00", "time_zone":"America\/Detroit", "event_title":"GLNT: The Galois module structure of Deligne--Lusztig varieties for $G=\\mathrm{GL}_3$", "occurrence_title":"", "combined_title":"GLNT: The Galois module structure of Deligne--Lusztig varieties for $G=\\mathrm{GL}_3$: Adithya Sathyanarayana (MSU)", "event_subtitle":"Adithya Sathyanarayana (MSU)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"Abstract: Deligne and Lusztig defined a finite \\'etale cover \\(Y(w) \\to X(w)\\) of varieties which is attached to any connected reductive group \\(\\mathbf{G}\\) defined over a finite field \\( \\mathbb{F}_q \\), with an isogeny \\(F\\) whose some positive power is a Frobenius endomorphism, and a Weyl group element \\(w \\in W\\). We consider the ramified Galois covers \\( \\overline{Y}(w)\\rightarrow \\overline{X}(w) \\) of the natural compactifications of these Deligne-Lusztig varieties. Our goal is to calculate the Lefschetz numbers for the action of the covering group, which is given by the points \\(\\mathbf{T}^{wF}\\) of a torus with values in \\(\\mathbb{F}_p\\), on the coherent cohomology of the structure sheaf of \\( \\overline{Y}(w)\\). \nThe full collection of Lefschetz numbers\ndetermine the virtual representation of \\(\\mathbf T^{wF}\\) on the\nalternating sum of these cohomology groups. In the two cases of Deligne--Lusztig surfaces of type \\(A_2\\) and \\(^{2}A_2\\) for \\( \\mathbf{G} = \\mathrm{GL}_3 \\), we give explicit formulas for the Lefschetz numbers for a generator of the stabilizer of an irreducible component of \\(\\overline{Y}(w)\\) .\nIt follows that the alternating coherent cohomology class of the full compactification \\(\\overline{Y}(w)\\) is not virtually free\nover the full covering group.", "occurrence_notes":null, "guid":"153898-21916610@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/153898", "building_id":"1000166", "building_name":"East Hall", "campus_maps_id":"53", "room":"4088", "location_name":"East Hall", "has_livestream":0, "cost":"", "tags":["Mathematics","Number Theory"], "website":"", "sponsors":[ { "group_name":"Group, Lie and Number Theory Seminar - Department of Mathematics", "group_id":"4892", "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":21916610 } , "151699-21911992": { "datetime_modified":"20260908T111907", "datetime_start":"20270208T160000", "datetime_end":"20270208T170000", "has_end_time":1, "date_start":"2027-02-08", "date_end":"2027-02-08", "time_start":"16:00:00", "time_end":"17:00:00", "time_zone":"America\/Detroit", "event_title":"TBA", "occurrence_title":"", "combined_title":"TBA: Eyal Goren (McGill)", "event_subtitle":"Eyal Goren (McGill)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "description":"TBA", "occurrence_notes":null, "guid":"151699-21911992@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/151699", "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":"Group, Lie and Number Theory Seminar - Department of Mathematics", "group_id":"4892", "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":21911992 } }