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X-WR-CALDESC:Events for Center for Complex Geometry
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TZID:Asia/Seoul
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TZOFFSETFROM:+0900
TZOFFSETTO:+0900
TZNAME:KST
DTSTART:20220101T000000
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20230301
DTEND;VALUE=DATE:20240229
DTSTAMP:20260417T100206
CREATED:20230425T013322Z
LAST-MODIFIED:20230504T065225Z
UID:2258-1677628800-1709164799@ccg.ibs.re.kr
SUMMARY:Insong Choe (최인송\, Konkuk University)
DESCRIPTION:Insong Choe (최인송) \nVisitor (2023.3.1-2024.2.28) from Konkuk University \nOffice: B255
URL:https://ccg.ibs.re.kr/event/230301-240228/
CATEGORIES:Visitors
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20231016T110000
DTEND;TZID=Asia/Seoul:20231016T120000
DTSTAMP:20260417T100206
CREATED:20231010T015222Z
LAST-MODIFIED:20231010T015241Z
UID:2580-1697454000-1697457600@ccg.ibs.re.kr
SUMMARY:Gil Bor\, Cusps of Caustics by Reflection in a Convex Billiard Table
DESCRIPTION:    Speaker\n\n\nGil Bor\nCIMAT\n\n\n\n\n\n\nPlace a point light source inside a smooth convex billiard table (or mirror). The n-th caustic by reflection is the envelope of light rays after n reflections. Theorem: each of these caustics\, for a generic point light source\, has at least 4 cusps. Conjecture: there are exactly 4 cusps iff the table is an ellipse. Here are the 2nd\, 5th and 8th caustics by reflection in an ellipse\, each with 4 cusps (marked by gray disks; the light source is the white disk) \n \nThis is a billiard version of “Jacobi’s Last Geometric Statement”\, concerning the number of cusps of the conjugate locus of a point on a convex surface\, proved so far only in the n=1 case. (Joint work with Serge Tabachnikov\, from Penn State\, USA).
URL:https://ccg.ibs.re.kr/event/2023-10-16-1100-1200/
LOCATION:B236-1\, IBS\, Korea\, Republic of
CATEGORIES:Complex Geometry Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20231016T160000
DTEND;TZID=Asia/Seoul:20231016T170000
DTSTAMP:20260417T100206
CREATED:20231010T015627Z
LAST-MODIFIED:20231010T015627Z
UID:2584-1697472000-1697475600@ccg.ibs.re.kr
SUMMARY:Gil Bor\, Bicycle Tracks\, their Monodromy Invariants and Geodesics
DESCRIPTION:    Speaker\n\n\nGil Bor\nCIMAT\n\n\n\n\n\n\nAt first sight\, the pair of front and back wheel tracks left by a passing bike on a sandy or muddy terrain seems like a random pair of curves. This is not the case. For example\, one can usually distinguish between the front and back wheel tracks\, and even the direction at which these were traversed\, based solely on their shapes. You can try it for the following pair of paths. \n \nAnother example: If the front wheel traverses a small enough closed path (compared to the bike size)\, then\, typically\, the back track does not close up\, by an amount approximated by the area enclosed by the front track and the bicycle length; this fact was utilized to build a simple area measuring mechanical device\, now obsolete\, called the Hatchet planimeter. \nIn recent years the subject has attracted attention due to newly discovered relations with the theory of completely integrable systems (the filament flow)\, sub-Riemannian geometry and elasticity theory. I will try to describe some of these developments and open questions.
URL:https://ccg.ibs.re.kr/event/2023-10-16-1600-1700/
LOCATION:B236-1\, IBS\, Korea\, Republic of
CATEGORIES:Complex Geometry Seminar
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