2 Higher Category Theory

Structure

• Chapter 6: Adjoint Functors
  • Section 6.1: Adjunctions in $2$-Categories
    • Subsection 6.1.1: Adjunctions
    • Subsection 6.1.2: Adjuncts
    • Subsection 6.1.3: Uniqueness of Adjoints
    • Subsection 6.1.4: Adjoints of Isomorphisms
    • Subsection 6.1.5: Composition of Adjunctions
    • Subsection 6.1.6: Duality in Monoidal Categories
  • Section 6.2: Adjoint Functors Between $\infty $-Categories
    • Subsection 6.2.1: Adjunctions of $\infty $-Categories
    • Subsection 6.2.2: Reflective Subcategories
    • Subsection 6.2.3: Correspondences
    • Subsection 6.2.4: Local Existence Criterion
    • Subsection 6.2.5: Digression: $\infty $-Categories with Short Morphisms
  • Section 6.3: Localization
    • Subsection 6.3.1: Localizations of $\infty $-Categories
    • Subsection 6.3.2: Existence of Localizations
    • Subsection 6.3.3: Reflective Localizations
    • Subsection 6.3.4: Stability Properties of Localizations
    • Subsection 6.3.5: Fiberwise Localization
    • Subsection 6.3.6: Universal Localizations
    • Subsection 6.3.7: Subdivision and Localization
• Chapter 7: Limits and Colimits
  • Section 7.1: Limits and Colimits
    • Subsection 7.1.1: Limits and Colimits in $\infty $-Categories
    • Subsection 7.1.2: Limit and Colimit Diagrams
    • Subsection 7.1.3: Preservation of Limits and Colimits
    • Subsection 7.1.4: Relative Initial and Final Objects
    • Subsection 7.1.5: Relative Limits and Colimits
    • Subsection 7.1.6: Limits and Colimits of Functors
  • Section 7.2: Cofinality
    • Subsection 7.2.1: Cofinal Morphisms of Simplicial Sets
    • Subsection 7.2.2: Cofinality and Limits
    • Subsection 7.2.3: Quillen's Theorem A for $\infty $-Categories
    • Subsection 7.2.4: Filtered $\infty $-Categories
    • Subsection 7.2.5: Local Characterization of Filtered $\infty $-Categories
    • Subsection 7.2.6: Left Fibrations over Filtered $\infty $-Categories
    • Subsection 7.2.7: Cofinal Approximation
    • Subsection 7.2.8: Sifted Simplicial Sets
  • Section 7.3: Kan Extensions
    • Subsection 7.3.1: Kan Extensions along General Functors
    • Subsection 7.3.2: Kan Extensions along Inclusions
    • Subsection 7.3.3: Relative Kan Extensions
    • Subsection 7.3.4: Kan Extensions along Fibrations
    • Subsection 7.3.5: Existence of Kan Extensions
    • Subsection 7.3.6: The Universal Property of Kan Extensions
    • Subsection 7.3.7: Kan Extensions in Functor $\infty $-Categories
    • Subsection 7.3.8: Transitivity of Kan Extensions
    • Subsection 7.3.9: Relative Colimits for Cocartesian Fibrations
  • Section 7.4: Limits and Colimits of $\infty $-Categories
    • Subsection 7.4.1: Limits of $\infty $-Categories
    • Subsection 7.4.2: Proof of the Diffraction Criterion
    • Subsection 7.4.3: Colimits of $\infty $-Categories
    • Subsection 7.4.4: Proof of the Refraction Criterion
    • Subsection 7.4.5: Limits and Colimits of Spaces
  • Section 7.5: Homotopy Limits and Colimits
    • Subsection 7.5.1: Homotopy Limits of Kan Complexes
    • Subsection 7.5.2: Homotopy Limits of $\infty $-Categories
    • Subsection 7.5.3: The Homotopy Limit as a Derived Functor
    • Subsection 7.5.4: Homotopy Limit Diagrams
    • Subsection 7.5.5: Categorical Limit Diagrams
    • Subsection 7.5.6: The Homotopy Colimit as a Derived Functor
    • Subsection 7.5.7: Homotopy Colimit Diagrams
    • Subsection 7.5.8: Categorical Colimit Diagrams
    • Subsection 7.5.9: Application: Filtered Colimits of $\infty $-Categories
  • Section 7.6: Examples of Limits and Colimits
    • Subsection 7.6.1: Products and Coproducts
    • Subsection 7.6.2: Powers and Tensors
    • Subsection 7.6.3: Pullbacks and Pushouts
    • Subsection 7.6.4: Examples of Pullback and Pushout Squares
    • Subsection 7.6.5: Equalizers and Coequalizers
    • Subsection 7.6.6: Sequential Limits and Colimits
    • Subsection 7.6.7: Small Limits
• Chapter 8: The Yoneda Embedding
  • Section 8.1: Twisted Arrows and Cospans
    • Subsection 8.1.1: The Twisted Arrow Construction
    • Subsection 8.1.2: Homotopy Transport for Twisted Arrows
    • Subsection 8.1.3: The Cospan Construction
    • Subsection 8.1.4: Cospans in $\infty $-Categories
    • Subsection 8.1.5: Thin $2$-Simplices of $\operatorname{Cospan}(\operatorname{\mathcal{C}})$
    • Subsection 8.1.6: Restricted Cospans
    • Subsection 8.1.7: Comparing $\operatorname{\mathcal{C}}$ with $\operatorname{Cospan}(\operatorname{\mathcal{C}})$
    • Subsection 8.1.8: Morphisms in the Duskin Nerve
    • Subsection 8.1.9: Cospan Fibrations
    • Subsection 8.1.10: Beck-Chevalley Fibrations
  • Section 8.2: Couplings of $\infty $-Categories
    • Subsection 8.2.1: Representable Couplings
    • Subsection 8.2.2: Morphisms of Couplings
    • Subsection 8.2.3: Representations of Couplings
    • Subsection 8.2.4: Presentations of Representable Couplings
    • Subsection 8.2.5: Adjunctions as Couplings
    • Subsection 8.2.6: Balanced Couplings
  • Section 8.3: The Yoneda Embedding
    • Subsection 8.3.1: Yoneda's Lemma
    • Subsection 8.3.2: Profunctors of $\infty $-Categories
    • Subsection 8.3.3: Hom-Functors for $\infty $-Categories
    • Subsection 8.3.4: Representable Profunctors
    • Subsection 8.3.5: Recognition of Hom-Functors
    • Subsection 8.3.6: Strict Models for Hom-Functors
  • Section 8.4: Cocompletion
    • Subsection 8.4.1: Dense Functors
    • Subsection 8.4.2: Density of Yoneda Embeddings
    • Subsection 8.4.3: Cocompletion via the Yoneda Embedding
    • Subsection 8.4.4: Example: Extensions as Adjoints
    • Subsection 8.4.5: Adjoining Colimits to $\infty $-Categories
    • Subsection 8.4.6: Recognition of Cocompletions
    • Subsection 8.4.7: Slices of Cocompletions
  • Section 8.5: Retracts and Idempotents
    • Subsection 8.5.1: Retracts in $\infty $-Categories
    • Subsection 8.5.2: Idempotents in Ordinary Categories
    • Subsection 8.5.3: Idempotents in $\infty $-Categories
    • Subsection 8.5.4: Idempotent Completeness
    • Subsection 8.5.5: Idempotent Completion
    • Subsection 8.5.6: Idempotent Endomorphisms
    • Subsection 8.5.7: Homotopy Idempotent Endomorphisms
    • Subsection 8.5.8: Partial Idempotents
    • Subsection 8.5.9: The Thompson Groupoid
  • Section 8.6: Conjugate and Dual Fibrations
    • Subsection 8.6.1: Conjugate Fibrations
    • Subsection 8.6.2: Existence of Conjugate Fibrations
    • Subsection 8.6.3: Dual Fibrations
    • Subsection 8.6.4: Existence of Dual Fibrations
    • Subsection 8.6.5: Cocartesian Duality via Cospans
    • Subsection 8.6.6: Comparison of Dual and Conjugate Fibrations
    • Subsection 8.6.7: The Opposition Functor
• Chapter 9: Large $\infty $-Categories
  • Section 9.1: Local Objects and Factorization Systems
    • Subsection 9.1.1: Local Objects
    • Subsection 9.1.2: Digression: Transfinite Composition
    • Subsection 9.1.3: Weakly Local Objects
    • Subsection 9.1.4: The Small Object Argument
    • Subsection 9.1.5: Lifting Problems in $\infty $-Categories
    • Subsection 9.1.6: Weak Factorization Systems
    • Subsection 9.1.7: Orthogonality
    • Subsection 9.1.8: Uniqueness of Factorizations
    • Subsection 9.1.9: Factorization Systems
  • Section 9.2: Truncated Objects of $\infty $-Categories
    • Subsection 9.2.1: Truncated Objects
    • Subsection 9.2.2: Example: Discrete and Subterminal Objects
    • Subsection 9.2.3: Truncated Morphisms
    • Subsection 9.2.4: Monomorphisms
• Chapter 10: Exactness and Animation
  • Section 10.1: Simplicial Objects of $\infty $-Categories
    • Subsection 10.1.1: Geometric Realization
    • Subsection 10.1.2: Semisimplicial Objects
    • Subsection 10.1.3: Skeletal Simplicial Objects
    • Subsection 10.1.4: Coskeletal Simplicial Objects
    • Subsection 10.1.5: The ČechNerve of a Morphism
    • Subsection 10.1.6: Split Simplicial Objects
  • Section 10.2: Regular $\infty $-Categories
    • Subsection 10.2.1: Sieves
    • Subsection 10.2.2: Quotient Morphisms
    • Subsection 10.2.3: Images
    • Subsection 10.2.4: Universal Quotient Morphisms
    • Subsection 10.2.5: Regular $\infty $-Categories