Triangulated and Derived Categories in Algebra and Geometry

Beijing Lectures, Spring 2022




Grading

Every even lecture will finish with one problem. Thus, there will be at most 12 of those. You need to write down a careful solution with all the details and send it to me via email. Every student who solves all the problems will successfully pass the course.




Lecture notes


Lecture 1

Slides


From monoids to categories, categorical monomorphisms and epimorphisms, products and equalizers through universal properties, initial and final objects.


References: [1, Section 1.2].


Lecture 2

Slides


More on functors, representability, limits and colimits, adjoint functors.


References: [1, Sections 1.3–1.5].


Homework: Before the next lecture be sure that you are comfortable with modules over (noncommutative) rings. A refresher can be found in [2, Section 1.2].


Lecture 3

Slides


More on adjoint functors, monoidal categories, enriched categories, (pre)additive categories and additive functors.


References: [1, Section 1.5], [3, Section VII.1], [2, Section 3.1].


Lecture 4

Slides


Adjoint functors and limits, additive functors, categories of complexes and homotopy categories, abelian categories and exactness.


References: [2, Sections 3.1–3.2, 4.1].


Lecture 5

Slides


Subobjects, injective and projective objects, generators, completeness and cocompleteness, Mitchell’s theorem.


References: [4, Chapters 2–4].


Lecture 6

Slides


Injective objects and (co)generators, Grothendieck categories, essential extensions and injective envelopes, weak embedding theorem.


References: [4, Chapter 6].


Lecture 7

Slides


Freyd–Mitchell theorem.


References: [4, Chapter 7].


Lecture 8

Slides


Serre subcategories, quotients, localization.


References: [5, Tags 02MN, 04VB].


Lecture 9

Slides


Categories of complexes, cones of morphisms, long exact sequence of cohomology, injective modules.


References: [6, Chapter 1].


Lecture 10

Slides


Classical derived functors.


References: [6, Chapter 2].


Lecture 11

Slides


Spectral sequences of double complexes, Grothendieck spectral sequence.


References: [6, Chapter 5].


Lecture 12

Slides


Balancing Tor, Grothendieck spectral sequence, examples, presheaves.


References: [6, Chapter 5], [7, Section 2.7].


Lecture 13

Slides


Sheaves, sheafification, triangulated categories.


References: [5, Chapter 6], [5, Sections 13.3–13.4].


Lecture 14

Slides


Injective resolutions for sheaves of abelian groups, homotopy category is triangulated.


References: [5, Sections 13.9–13.10].


Lecture 15

Slides


Homotopy category is triangulated, localization of triangulated categories.


References: [8, Sections IV.1–IV.2].


Lecture 16

Slides


Localization of subcategories, triangulated quotient categories.


References: [5, Section 13.6].


Lecture 17

Slides


Localization of functors, semiorthogonal decompositions, derived functors.


References: [2, Section 5.3], [8, Section III.6].


Lecture 18

Slides


Deligne’s construction of derived functors.


References: [5, Section 13.14].


Lecture 19

Slides


Composition of derived functors, derived bifunctors, t-structures.


References: [9, Section 1.3].


Lecture 20

Slides


Properties of t-structures.


References: [9, Section 1.3].


Lecture 21

Slides


Heart of a t-structure, flabby sheaves.


References: [9, Section 1.3], [10, Section II.2.4].


Lecture 22

Slides


A brief overview of sheaf theory.


References: [10, Section II.2].


Lecture 23

Slides


Derived categories of sheaves.


References: [10, Section II.2].


Lectue 24

Slides


Local systems, constructible sheaves, perverse sheaves.


References: [9, 10].




References


  1. M. Kashiwara, P. Schapira, Categories and Sheaves.
  2. P. Schapira, Categories and Homological Algebra. pdf
  3. S. Mac Lane, Categories for the Working Mathematician.
  4. P. Freyd, Abelian Categories.
  5. The Stacks Project.
  6. C. Weibel, An Introduction to Homological Algebra.
  7. R. Vakil, Foundations of Algebraic Geometry. pdf
  8. S. Gelfand, Yu. Manin, Methods of Homological Algebra.
  9. A. Beilinson, J. Bernstein, P. Deligne, Faisceaux Pervers. pdf
  10. M. Kashiwara, P. Schapira, Sheaves on Manifolds.