1. CMB 2008 (vol 51 pp. 125)
|Explicit Real Cubic Surfaces |
The topological classification of smooth real cubic surfaces is recalled and compared to the classification in terms of the number of real lines and of real tritangent planes, as obtained by L.~Schl\"afli in 1858. Using this, explicit examples of surfaces of every possible type are given.
Categories:14J25, 14J80, 14P25, 14Q10
2. CMB 1997 (vol 40 pp. 352)
|A New Proof of a Theorem of Magnus |
Using naive algebraic geometric methods a new proof of the following celebrated theorem of Magnus is given: Let $G$ be a group with a presentation having $n$ generators and $m$ relations. If $G$ also has a presentation on $n-m$ generators, then $G$ is free of rank $n-m$.
Categories:20E05, 20C99, 14Q99