(Unofficial) Topics in Algebraic Geometry
Fall 2010

Instructor:  Karl Schwede
Text:  Frobenius Splitting Methods in Geometry and Representation Theory
by Michel Brion and Shrawan Kumar (we will probably use this text 30-40% of the time).
Syllabus:   Click here


Supported partially by the National Science Foundation DMS #1064485:   Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).

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Please let me know if you find typos in the notes.

Notes from the lectures:

  •  All the notes so far in one PDF file: Click here. 114 pages total.

  •  8-26-2010   PDF    We introduce using Frobenius to measure singularities. We showed that regular rings have flat F_* R-modules. We also proved some basic facts about Frobenius splittings.
  •  8-31-2010   PDF    We show that F_* R being flat implies that R is regular. We also begin Fedder's criteria, the result that will give us a very effective method for checking whether a ring is F-split.
  •  9-2-2010   PDF    We prove Fedder's criteria for F-splitting/purity We also proved some more basic facts about F-splittings and started looking at normality.
  •  9-7-2010   PDF    We study how non-normal Frobenius split varieties can be, and classify one dimensional F-split singularities.
  •  9-9-2010   PDF    We study projective varieties and when they are Frobenius split.
  •  9-14-2010   PDF    We finish up some things from the previous time and we begin our study of rational singularities.
  •  9-17-2010   PDF    We continue to study Cohen-Macaulay and rational singularities, including in the graded case.
  •  9-21-2010   PDF    We study deformations of rationality and F-purity.
  •  9-23-2010   PDF    We introduce F-rationality.
  •  9-28-2010   PDF    We continue to study F-rationality and also discuss reduction to characteristic p.
  •  9-30-2010   PDF    We prove that rational singularities are F-rational type (modulo a hard lemma) and also started talking about log canonical and log terminal singularities.
  •  10-5-2010   PDF    We continue our study of log canonical and log terminal singularities. Then we begin our study of singularities of pairs in positive characteristic.
  •  10-7-2010   PDF    We define notions of singularities of pairs in positive characteristic. We begin our description of how these change under birational maps.
  •  10-19-2010   PDF    We prove that the test ideal and the multiplier ideal coincide after reduction to characteristic p >> 0.
  •  10-26-2010   PDF    We study analogs of log canonical centers in characteristic p > 0.
  •  10-28-2010   PDF    We discuss more properties of F-pure centers, we begin our discussion on killing local cohomology with finite maps.
  •  11-9-2010   PDF    We discuss Matlis and local duality and also discuss more about F-rationality.
  •  11-11-2010   PDF    We discuss vanishing up to finite maps and also begin our discussion of tight closure.
  •  11-16-2010   PDF    We continue to discuss tight closure. We also mention Hilbert-Kunz multiplicity.
  •  11-18-2010   PDF    We finish our discussion of tight closure, and we begin our proof of Hara's surjectivity lemma.
  •  11-23-2010   PDF    We finish our proof of Hara's surjectivity lemma.
  •  11-30-2010   PDF    We talk about globally F-regular varieties and the Mehta-Ramanathan criteria for Frobenius splitting.
  •  12-2-2010   PDF    We finish our discussion of the Mehta-Ramanathan criteria for Frobenius splitting, briefly discuss diagonally Frobenius split varieties, and also a discussion of Frobenius splittings of toric varieties.
  •  12-7-2010   PDF    We talk about failure of Kodaira-type vanishing in positive characteristic.
  •  12-9-2010   PDF    We discuss Fujita's conjecture in positive characteristic.

    Exercises:

  •  Exercises #1