4 hours lecture + 2 hours exercise session

Winter term 2019/2020

Veranstaltungsnummer: 3314430

First lecture: 16.10.2019

**Exercise session:** Fridays 11:00-12:30 in room 1.013 (RUD 25)

Veranstaltungsnummer: 33144301

First exercise session: 18.10.2019

*11.06.2019*: The first lecture will take place on Wednesday 16.10.2019.*11.06.2019*: This course is a BMS course and is therefore held in English.*23.07.2019*: To avoide collisions with other lectures the time and place of the lecture has changed.*23.09.2019*: Lecture notes from last semesters course on Topology I are now available further down on this page.*15.10.2019*: On Friday 18.10. there will be no exercise session, instead there wil be an additional lecture. On Wednesday 23.10. there will be an exercise session instead of the lecture.*18.10.2019*: Since the old room was far too small, the Friday lecture and the exercise session will take place in room 1.013 (starting from next week).*29.11.2019*: The lecture on Wednesday 4.12. will be cancelled and (if necessary) added at the end of the semester.*27.01.2020*: Exam: The exam will take place at Wednesday, 4.3.2020, 09:00-11:00 in room 0'313 (RUD 26). Please register for it in due time. You can have a look in your exam at Friday, 6.3.2020, 10:00-11:00 in room 0'318 (RUD 26).*14.01.2020*: In the winter term 2020/2021 an advanced seminar on selected topics of algebraic and differential topology will be offered, in which further topics will be discussed, which were not discussed in this lecture due to lack of time.*14.01.2020*: In the summer term 2020 a two-hour lecture on 3-manifolds will be offered, in which we will investigate methods to present and analyze 3-manifolds.*09.05.2020*: The second exam will take place at 2. June 2020 at 8:00 as a take home exam, you will get all details via e-mail.

**Prerequisites:** Prerequisites are the introductory lectures (Analysis I, II and Linear Algebra I, II),
elementary algebra (groups, homomorphisms, rings, etc.), and the lecture Topology I (in particular the fundamental group and simplicial homology).

**Exam:** The exam will take place at Wednesday, 4.3.2020, 09:00-11:00 in room 0'313 (RUD 26).

**Second exam:** The second exam takes places at Tuesday, 2.6.2020, online (see information above).

Criterion for admission to the final examination: For this lecture an admission restriction to the final examination
is unfortunately not permitted. Nevertheless, I would like to encourage you to regularly work on the exercise sheets. I recommend taking the exam if at least
50% of the exercises have been solved correctly.

Sheet 1 (pdf)

Sheet 2 (pdf)

Sheet 3 (pdf)

Sheet 4 (pdf)

Sheet 5 (pdf)

Sheet 6 (pdf)

Sheet 7 (pdf)

Sheet 8 (pdf) (A typo in Exercise 2 has been corrected. It should be the wedge sum instead of the Cartesian product.)

Sheet 9 (pdf)

Sheet 10 (pdf)

Sheet 11 (pdf)

Sheet 12 (pdf)

Sheet 13 (pdf)

Sheet 14 (pdf)

Sheet 15 (pdf)

2.1. Definition, functoriality and first computations

2.2. Homotopy groups of spheres

2.3. Relative homotopy groups and the long exact sequence of a pair

2.4. The Hopf fibration and the long exact sequence of a fibration

3.1. Definition and functoriality

3.2. Relative homology groups

3.3. The long exact sequence of a pair

3.4. Excision

3.5. The Jordan-Brouwer splitting theorem

3.6. The Eilenberg-Steenrod axioms

4.1. CW complexes

4.2. Cellular homology groups

4.3. Equivalence of cellular homology and singular homology

4.4. The local degree of a map

4.5. Proof of Whitehead's theorem

4.6. Proof of Hurewicz's theorem

5.1. Tensor products

5.2. Homology with coefficients

5.3. The Tor functor and the universal coefficient theorem

5.4. Künneth's formula and the homology of a cartesian product

5.5. Persistent homology and topological analysis of data

6.1. Dualizing a chain complex

6.2. The universal coefficient theorem for cohomology

6.3. Singular and cellular cohomology

6.4. Graded Rings

6.5. The cup product

6.6. Calculations of cohomology rings

6.7. Cross products and Künneth's formula for cohomology

6.8. The dimension of real division algebras

7.1. The cap product and the Poincaré isomorphism

7.2. First applications of Poincaré duality

7.3. Poincaré duality via simplicial cohomology

7.4. Cohomology with compact support

7.5. The general proof of Poincaré duality

8.1. The intersection form and classification of manifolds

8.2. Tangent spaces and transverse intersections

8.3. Algebraic intersection numbers and the intersection form

Carolin Wengler has made the effort to format her lecture notes from the last semester lovingly with LaTeX and kindly made them available to me. (If you find errors, including smaller typos, please report them to me, such that I can correct them.)

Carolin Wengler's lecture notes (pdf) (in German)

For the basics from the last semester (point set topology, fundamental group and simplicial homology theory) I recommend the books by M. Armstrong and K. Jänich. A very popular textbook on (algebraic) topology is the book by A. Hatcher. In addition, I would also like to recommend you the lecture notes by S. Friedl and C. Wendl, and the books by G. Bredon and A. Fomenko and D. Fuchs.

Further material in supplement or parallel to the lecture:

We did not discussed a proof of the smooth (generalized) Schoenflies theorem, since it uses differential topology and is thus not really fitting into the topic of this lecture. However, the proof uses a beutiful argument which is not too hard to understand. A proof can be found (apart from the original works) for example in:

Some animations parallel to the constructions via pictures in lecture can be found here:

An animation visualizing the construction of Alexander's horned sphere.

A visualization of the Hopf fibration.

Some interesting 3D-animations (mostly fitting to last semesters topics) can be found on Neil Strickland's webpage.

For details about Boy's embedding of the real projective plane into Euclidean 3-space I suggest:

The Youtube video by Jos Leys,

the construction method by Arnaud Chéritat, and

the short article by Robion Kirby.

For more information about persistent homology I recommend the book by Edelsbrunner and Harer (assuming no prior knowledge in topology) and the book project by Polterovich, Rosen, Samvelyan and Zhang.

For further reading I suggest the above mentioned Skript by S. Friedl and the book by A. Fomenko and D. Fuchs. For information on 4-manifold the book by A. Scorpan is a good starting point. For more general differential topology I suggest: