# Week 4

## Schedule

Summary | Solutions | Time (min) |
---|---|---|

Lecture 5 | ||

* category (18:55) | ||

* category, intuitively (50:00) | ||

* \(\mathbf{Cat}\) (51:50) | ||

AC0: Chapter II | ||

* groups are monoids where all morphisms are automorphisms (Joke 1.1, SSC EX 3.32) | ||

SSC: Chapter 3 | * PS2 5 | 5 |

* category (D 3.6) | * PS2 6 | 5 |

* free category (D 3.7) | * PS2 7 | 10 |

* preorders as categories, preorder reflection of a category (3.2.3) | ||

* \(\mathcal{V}\)-categories are not categories with extra structure (R 3.26) | ||

* formalizing the notion of sameness (remark before D 3.28), isomorphism (D 3.28) | ||

* sets and functions as databases, particularly "unclear whether right-hand column exhaust all of B" (3.3.1) | ||

Total | 20 |