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X-WR-CALDESC:évènements pour Département de mathématiques et applications
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TZID:Europe/Paris
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TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20220327T010000
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DTSTART;TZID=Europe/Paris:20220218T140000
DTEND;TZID=Europe/Paris:20220218T153000
DTSTAMP:20260406T151200
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LAST-MODIFIED:20220204T103815Z
UID:15163-1645192800-1645198200@www.math.ens.psl.eu
SUMMARY:The Kemperman inverse 	problem
DESCRIPTION:Let G be a connected locally compact group with a left Haar measure μ\, and let A\,B ⊆ G be nonempty and compact. Assume further that G is unimodular\, i.e.\, μ is also the right Haar measure; this holds\, e.g.\, when G is compact\, a nilpotent Lie group\, or a semisimple Lie group. In 1964\, Kemperman showed that \nμ(AB) ≥ min {μ(A)+μ(B)\, μ(G)} .\nThe Kemperman inverse problem (proposed by Griesmer\, Kemperman\, and Tao) asks when the equality happens or nearly happens. I will discuss the recent solution of this problem\, highlighting the connections to model theory. (Joint with Jinpeng An\, Yifan Jing\, and Ruixiang Zhang).
URL:https://www.math.ens.psl.eu/evenement/the-kemperman-inverse-problem/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
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DTSTART;TZID=Europe/Paris:20220218T154500
DTEND;TZID=Europe/Paris:20220218T171500
DTSTAMP:20260406T151200
CREATED:20220203T145355Z
LAST-MODIFIED:20220211T161457Z
UID:15158-1645199100-1645204500@www.math.ens.psl.eu
SUMMARY:Not Pfaffian
DESCRIPTION:This talk describes the connection between /strong minimality/ of the differential equation satisfied by an complex analytic function and the real and imaginary parts of the function being /Pfaffian/. The talk will not assume the audience knows these notions previously\, and will attempt to motivate why each of them are important notions in various areas. The connection we give\, combined with a theorem of Freitag and Scanlon (2017) provides the answer to a question of Binyamini and Novikov (2017). We also answer a question of Bianconi (2016). We give what seem to be the first examples of functions which are definable in o-minimal expansions of the reals and are differentially algebraic\, but not Pfaffian.
URL:https://www.math.ens.psl.eu/evenement/not-pfaffian/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
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