Skript Schulmathematik pdf (Version 25.08.22)

Vorlesung in Stuttgart, SoSe 22
Anleitung Computerpraktikum pdf (Version 21.03.22)

Computerpraktikum in Stuttgart (erster von 2 Blöcken), WiSe 21/22
Anleitung Computerpraktikum pdf (Version 12.05.19)

Computerpraktikum in Stuttgart (erster von 3 Blöcken), SoSe 19
Anleitung Computerpraktikum pdf (Version 07.04.20) (Links zu Galerien mit Graphiken.)

Computerpraktikum in Stuttgart (erster von 3 Blöcken), WiSe 18/19
Anleitung Computerpraktikum dvi ps pdf (Version 08.12.17)

Computerpraktikum in Stuttgart (erster von 3 Blöcken), WiSe 17/18
Skript Algebraische Zahlentheorie dvi ps pdf (Version 19.10.23)

Vorlesung in Stuttgart, WiSe 14/15
Skript Gewöhnliche Darstellung endlicher Gruppen dvi ps pdf (Version 10.09.15)

Vorlesung in Stuttgart, SoSe 11
Skript Computeralgebra dvi ps pdf (Version 13.04.18)

Vorlesung in Stuttgart, WiSe 10/11
Skript Mathematik für Wirtschaftswissenschaftler pdf (Version 21.03.22)

Vorlesung in Stuttgart, Teil I WiSe 10/11, Teil II SoSe 11, Teil I WiSe 11/12
Anleitung Computerpraktikum dvi ps pdf (Version 18.11.11)

Computerpraktikum in Stuttgart (erster von 3 Blöcken), WiSe 10/11
Skript Liealgebren dvi ps pdf

Vorlesung in Stuttgart, SoSe 10; Vorlesung in Stuttgart, SoSe 14.
Skript Homologische Algebra dvi ps pdf

Vorlesung in Bremen, WiSe 09/10; Vorlesung in Stuttgart, SoSe 10.
Skript Topologie dvi ps pdf (Version 18.11.10, sin_x_inv.eps)

Vorlesung in Koblenz, SoSe 09.
Skript Galoistheorie dvi ps pdf (Version 10.07.19)

Vorlesung in Koblenz, WiSe 08/09.
Skript Cohomologie von Gruppen dvi ps pdf (Version 11.09.17)

Vorlesung in Aachen, SoSe 05, fortgesetzt WiSe 05/06.
Einfachheit von PSL dvi ps pdf

Proseminarvortrag in Aachen, WiSe 04/05
Skript Lineare Algebra für Informatiker dvi ps pdf (Version 23.06.14)

Vorlesung in Ulm, WiSe 02/03 und WiSe 03/04.

A counterexample on nilpotent endomorphisms in triangulated categories dvi ps pdf

We give a counterexample to an assertion on nilpotent endomorphisms of degree 3 in triangulated categories. Roughly speaking, it is in general not possible to lower the nilpotency degree by passing to a certain cone.
(jt. w. Theo Bühler) Some elementary considerations in exact categories dvi ps pdf (Version 02.07.14)

We give counterexamples to some elementary assertions in exact categories and derive some lemmata directly from the axioms.
Dweak squares in Heller triangulated categories dvi ps pdf

We discuss a compatibility between distinguished weak (dweak) squares with the shift functor, which holds in a closed Heller triangulated category. It can be formulated in a Verdier triangulated category as well, but I do not know whether it can be proven there.
Remarks on the axioms for exact categories: (Ex 2) is redundant; if idempotents split, then first to pure mono is pure mono dvi ps pdf

The axiom (Ex 2) in the axiomatisation of exact categories as in "Heller triangulated categories" dvi ps pdf, §A.2, is redundant. Moreover, if idempotents split, then the first morphism in a composition yielding a pure monomorphism, is purely monomorphic.
A construction principle for Frobenius categories dvi ps pdf

This is a supplement to "Heller triangulated categories" dvi ps pdf. We exhibit a structure of a Frobenius category on a category of diagrams appearing in loc. cit., using a general principle.
A relative Yoneda Lemma dvi ps pdf

We construct set-valued right Kan extensions via a relative Yoneda Lemma.
On the center of the derived category dvi ps pdf

Rickard observed that in general, the center of the bounded derived category of a ring is strictly bigger than the center of the ring (unpublished). We give a simple example.


Einführung Mathematik (2023) pdf
Extremale Punkte und Kurven (für den Tag der Mathematik, Heilbronn, 2019) pdf
Hütchenspiel und Zahlentheorie (für Science Espresso in Stuttgart, 2019) pdf
Auflösungen (Antrittsvorlesung Stuttgart) pdf, Slides dazu pdf

Heuristics concerning primes, following Greg Martin pdf

We give an integral variant of Greg Martin's heuristic argument for the asymptotic behaviour of the number of primes.
Does "Quillen A with an extra direction" hold? dvi ps pdf

The assertion in question is a bicategorical version of Quillen A, where in the "new" direction "nothing happens". I do not know whether it holds or not. I also sketched an idea how one might approach this question. I would be grateful for arguments, counterexamples (also to that idea), references, for anything.