Zum 200. Geburtstag von Evariste Galois
We throw a brief glance at Galois' life, on the occasion of his 200th anniversary (written in German).
math.HO↗
arXiv subjects
Markus Wessler
Publications and source records attributed to Markus Wessler.
Extended visual cryptography systems
Visual cryptography schemes have been introduced in 1994 by Naor and Shamir. Their idea was to encode a secret image into $n$ shadow images and to give exactly one such shadow image to each member of a group $P$ of $n$ persons. Whereas most work in recent years has been done concerning the problem of qualified and forbidden subsets of $P$ or the question of contrast optimizing, in this paper we study extended visual cryptography schemes, i.e. shared secret systems where any subset of $P$ shares its own secret.
math.CO↗
The largest small polytopes
The aim of this paper is the determination of the largest $n$-dimensional polytope with $n+3$ vertices of unit diameter. This is a special case of a more general problem proposed by Graham.
math.CO↗
Weak Positivity and Dyson's Lemma
We state and prove a version of Dyson's Lemma for a product of smooth projective varieties of arbitrary dimension using positivity methods.
math.AG↗
An algebraic proof of Iitaka's Conjecture C_{2,1}
We give a proof of Iitaka's Conjecture C_{2,1} using only elementary methods from algebraic geometry. The main point is that, given a non-isotrivial and relatively minimal family f : X \to B, where X is a surface and B is a curve, both smooth and projective, we show that the direct image of the relatively canonical sheaf has strictly positive degree.
math.AG↗