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SUMMARY:Jeff Achter (Colorado State University)
DTSTART:20251103T210000Z
DTEND:20251103T220000Z
DTSTAMP:20260423T040046Z
UID:NTBU/33
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/NTBU/33/">Re
 gular homomorphisms\, with a twist</a>\nby Jeff Achter (Colorado State Uni
 versity) as part of Boston University Number Theory Seminar\n\nLecture hel
 d in CDS Room 548 in Boston University.\n\nAbstract\nLet $X$ be a smooth p
 rojective variety over a field.  If the field is $\\mathbb C$\, Griffiths 
 associates to $X$ an algebraic intermediate Jacobian $J$\, which is a comp
 lex abelian variety which captures some information about pointed families
  of algebraic cycles on $X$.  More generally\, a regular homomorphism to a
 n abelian variety accomplishes something similar for pointed families of a
 lgebraic\ncycles on a variety over any perfect field.\n\nFor families of c
 ycles which don't admit a point over the field of\ndefinition\, we obtain 
 instead a map to a torsor under that abelian\nvariety.  I'll explain these
  results and what they tell us about the\nrationality of certain threefold
 s.    (Joint work with Sebastian\nCasalaina-Martin and Charles Vial.)\n
LOCATION:https://researchseminars.org/talk/NTBU/33/
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