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SUMMARY:Susanna Zimmerman (Université d'Angers)
DTSTART:20201106T180000Z
DTEND:20201106T193000Z
DTSTAMP:20260423T035825Z
UID:CAGS/2
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/CAGS/2/">Sig
 nature morphisms of Cremona groups</a>\nby Susanna Zimmerman (Université 
 d'Angers) as part of Columbia algebraic geometry seminar\n\n\nAbstract\nA 
 Cremona group Cr(n) is the groupe of birational self-maps of a projective 
 space of dimension n. It is an algebraic group if n=1 and it is not of fin
 ite dimension for n>1\, in fact\, it contains a polynomial ring in n- vari
 ables. We are interested in homomorphism from Cr(n) to a finite group. For
  n=2 and the base-field over complex numbers\, no such quotient can exist\
 , basically because birational maps only contract rational curves. Over no
 n-closed fields and in higher dimension\, there are many birational maps c
 ontracting non-rational subvarieties\, and it turns out that there are man
 y homomorphisms from Cr(n) to a finite group. In this talk I explain and m
 otivate this phenomenon in dimension 2 and in dimension 3.\n
LOCATION:https://researchseminars.org/talk/CAGS/2/
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