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SUMMARY:Linquan Ma (Purdue University)
DTSTART:20211221T170000Z
DTEND:20211221T180000Z
DTSTAMP:20260423T040001Z
UID:ZAG/174
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/ZAG/174/">Th
 e cohomology table of coherent sheaves on singular projective varieties</a
 >\nby Linquan Ma (Purdue University) as part of ZAG (Zoom Algebraic Geomet
 ry) seminar\n\n\nAbstract\nThe cohomology table of a coherent sheaf on a p
 rojective variety is numerical data of the dimension of each cohomoogy gro
 up of each twist of the sheaf. Eisenbud--Schreyer give a description of th
 e cone of cohomology table of vector bundles and coherent sheaves on proje
 ctive spaces. This leads to their proof of the Boij--Soderberg theory whic
 h describes the cone spanned by the Betti tables of graded modules over po
 lynomial rings. In this talk\, we give some extensions of these results of
  Eisenbud--Schreyer to singular projective varieties and singular standard
  graded rings. Our central technique is to use a sequence of coherent shea
 ves that behave like an Ulrich sheave asymptotically. We call such sequenc
 e a lim Ulrich sequence of sheaves and we can prove their existence in pos
 itive characteristic. This talk is largely based on joint work in progress
  with Srikanth Iyengar and Mark Walker.\n
LOCATION:https://researchseminars.org/talk/ZAG/174/
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