Math Writing

Grothendieck Spectral Sequences

Introduces Grothendieck spectral sequences and proves their existence, followed by two examples: base-change for Tor and Ext.

The Dual Isogeny

Proves the existence of the dual isogeny to an isogeny of two elliptic curves, then establishes some of its basic properties.

Simplicial Approximation

Introduces simplicial approximation, then uses barycentric subdivision and generalized barycentric subdivision to prove the general simplicial approximation theorem.

Čech-Kohomologie

Covers Čech cohomology of abelian sheaves on topological spaces with respect to a given open covering. The main result: Čech cohomology and regular cohomology of quasi-coherent sheaves on noetherian separated schemes coincide.

Adjunktionen 1

Introduces adjunctions in category theory. Three equivalent definitions are given, with an excursus on reflective subcategories.

Das Banach-Tarski-Paradoxon

Explains and proves the Banach–Tarski paradox, along with similar, easier paradoxes like the Sierpiński–Mazurkiewicz paradox and the Hausdorff paradox.