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BEGIN:VEVENT
SUMMARY:János Kollár (Princeton University)
DTSTART:20200418T160000Z
DTEND:20200418T170000Z
DTSTAMP:20260416T115259Z
UID:Wagon/1
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/1/">Wh
 at determines a variety?</a>\nby János Kollár (Princeton University) as 
 part of Western Algebraic Geometry ONline\n\n\nAbstract\nIn this talk we w
 ill discuss topological properties of varieties with many rational points 
 over a function field\, and present joint work-in-progress with Erwan Rous
 seau. More precisely\, we define a smooth projective variety X over the co
 mplex numbers to be geometrically-special if there is a dense set of close
 d points S in X such that\, for every x in S\, there is a pointed curve (C
 \,c) and a sequence of morphisms (C\,c)->(X\,x) which covers C x X\, i.e.\
 , the union of their graphs is Zariski-dense in C x X. Roughly speaking\, 
 a variety is geometrically-special if it satisfies density of "pointed" ra
 tional points over some function field. Inspired by conjectures of Campana
  on special varieties and Lang on hyperbolic varieties\, we prove that eve
 ry linear quotient of the fundamental group pi_1(X) of such a variety is v
 irtually abelian.\n
LOCATION:https://researchseminars.org/talk/Wagon/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mauricio Velasco (Universidad de los Andes)
DTSTART:20200418T200000Z
DTEND:20200418T202500Z
DTSTAMP:20260416T115259Z
UID:Wagon/2
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/2/">So
 me vignettes on sums-of-squares on varieties</a>\nby Mauricio Velasco (Uni
 versidad de los Andes) as part of Western Algebraic Geometry ONline\n\n\nA
 bstract\nI will review some classical questions on the relationship betwee
 n nonnegative polynomials and sums of squares in R^n and briefly survey th
 eir generalizations to the context of real projective varieties. The resul
 ts presented in this talk are joint work with Greg Blekherman\, Rainer Sin
 n and Greg G. Smith.\n
LOCATION:https://researchseminars.org/talk/Wagon/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Juliette Bruce (University of Wisconsin\, Madison)
DTSTART:20200418T203500Z
DTEND:20200418T210000Z
DTSTAMP:20260416T115259Z
UID:Wagon/3
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/3/">Se
 mi-ample asymptotic syzygies</a>\nby Juliette Bruce (University of Wiscons
 in\, Madison) as part of Western Algebraic Geometry ONline\n\n\nAbstract\n
 I will discuss the asymptotic non-vanishing of syzygies for products of pr
 ojective spaces\, generalizing the monomial methods of Ein-Erman-Lazarsfel
 d. This provides the first example of how the asymptotic syzygies of a smo
 oth projective variety whose embedding line bundle grows in a semi-ample f
 ashion behave in nuanced and previously unseen ways.\n
LOCATION:https://researchseminars.org/talk/Wagon/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicolas Addington (University of Oregon)
DTSTART:20200418T211000Z
DTEND:20200418T213500Z
DTSTAMP:20260416T115259Z
UID:Wagon/4
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/4/">Ra
 tional points and derived equivalence</a>\nby Nicolas Addington (Universit
 y of Oregon) as part of Western Algebraic Geometry ONline\n\n\nAbstract\nF
 or smooth projective varieties over Q\, is the existence of a rational poi
 nt preserved under derived equivalence? First I'll discuss why this questi
 on is interesting\, and what is known. Then I'll show that the answer is n
 o\, giving two counterexamples: an abelian variety and a torsor over it\, 
 and a pair of moduli spaces of sheaves on a K3 surface.\n
LOCATION:https://researchseminars.org/talk/Wagon/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Claire Voisin (Collège de France)
DTSTART:20200419T160000Z
DTEND:20200419T170000Z
DTSTAMP:20260416T115259Z
UID:Wagon/5
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/5/">Sc
 hiffer variations of hypersurfaces and the generic Torelli theorem</a>\nby
  Claire Voisin (Collège de France) as part of Western Algebraic Geometry 
 ONline\n\n\nAbstract\nThe generic Torelli theorem for hypersurfaces of deg
 ree d and dimension n-1 was proved by Donagi in the 90's. It works under t
 he assumption that d is at least 7 and d does not divide n+1\, which in pa
 rticular excludes the Calabi-Yau case in all dimensions. We prove that the
  generic Torelli theorem for hypersurfaces holds with finitely many except
 ions. A key tool is the notion of Schiffer variation of a hypersurface and
  how to characterize them by looking at the variation of Hodge structure a
 long them.\n
LOCATION:https://researchseminars.org/talk/Wagon/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valentijn Karemaker (Utrecht)
DTSTART:20200419T173500Z
DTEND:20200419T175500Z
DTSTAMP:20260416T115259Z
UID:Wagon/6
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/6/">Ma
 ss formula for supersingular abelian threefolds</a>\nby Valentijn Karemake
 r (Utrecht) as part of Western Algebraic Geometry ONline\n\n\nAbstract\nUs
 ing the theory of polarised flag type quotients\, we determine mass formul
 ae for all principally polarised supersingular abelian threefolds defined 
 over an algebraically closed field k of characteristic p. We combine these
  results with computations of the automorphism groups to study Oort's conj
 ecture\; we prove that every generic principally polarised supersingular a
 belian threefold over k of characteristic >2 has automorphism group \\( \\
 mathbb{Z}/2\\mathbb{Z} \\).\n
LOCATION:https://researchseminars.org/talk/Wagon/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ariyan Javanpeykar (University of Mainz)
DTSTART:20200419T180500Z
DTEND:20200419T183000Z
DTSTAMP:20260416T115259Z
UID:Wagon/7
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/7/">Al
 banese maps and fundamental groups of varieties with many rational points 
 over function fields</a>\nby Ariyan Javanpeykar (University of Mainz) as p
 art of Western Algebraic Geometry ONline\n\n\nAbstract\nIn this talk we wi
 ll discuss topological properties of varieties with many rational points o
 ver a function field\, and present joint work-in-progress with Erwan Rouss
 eau. More precisely\, we define a smooth projective variety X over the com
 plex numbers to be geometrically-special if there is a dense set of closed
  points S in X such that\, for every x in S\, there is a pointed curve (C\
 ,c) and a sequence of morphisms (C\,c)->(X\,x) which covers C x X\, i.e.\,
  the union of their graphs is Zariski-dense in C x X. Roughly speaking\, a
  variety is geometrically-special if it satisfies density of "pointed" rat
 ional points over some function field. Inspired by conjectures of Campana 
 on special varieties and Lang on hyperbolic varieties\, we prove that ever
 y linear quotient of the fundamental group pi_1(X) of such a variety is vi
 rtually abelian.\n
LOCATION:https://researchseminars.org/talk/Wagon/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johan de Jong (Columbia)
DTSTART:20200419T184000Z
DTEND:20200419T190500Z
DTSTAMP:20260416T115259Z
UID:Wagon/8
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/Wagon/8/">Af
 fineness of the complement of the ramification locus</a>\nby Johan de Jong
  (Columbia) as part of Western Algebraic Geometry ONline\n\n\nAbstract\nTh
 e purpose of this talk is to encourage people to think about purity questi
 ons. We will discuss a strong form of purity for morphisms of relative dim
 ension 0. For morphisms of relative dimension 1 we relate the purity quest
 ion to one on purity for families of curves.\n
LOCATION:https://researchseminars.org/talk/Wagon/8/
END:VEVENT
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