The inner-product of iso-taxicab geometry.
The intersection conics of six straight lines.
The lattices and Möbius functions of stable closed subrootsystems and Hyperplane complements for classical Weyl Groups.
The Lehmus inequality.
The length of a lemmiscate.
The length of a unitary transformation.
The length of a unitary transformation for characteristic 2.
The Mathieu group and its pseudogroup extension .
The maximum size of a partial spread in is .
The minimum rank problem over finite fields.
The minimum size of complete caps in .
The Missing Seventh Circle.
The Möbius-Pompeiu metric property.
The n -Point Condition and Rough CAT(0)
We show that for n ≥ 5, a length space (X; d) satisfies a rough n-point condition if and only if it is rough CAT(0). As a consequence, we show that the class of rough CAT(0) spaces is closed under reasonably general limit processes such as pointed and unpointed Gromov-Hausdorff limits and ultralimits.
The Neuberg cubic in locus problems.
The nine points circle and Euler's line. (El círculo de los nueve puntos y la recta de Euler.)
The nonexistence of certain projective planes of order 15.
The Nonexistence of Certain Topological Polygons.
The Nonexistence of some Griesmer Arcs in PG(4, 5)
In this paper, we prove the nonexistence of arcs with parameters (232, 48) and (233, 48) in PG(4,5). This rules out the existence of linear codes with parameters [232,5,184] and [233,5,185] over the field with five elements and improves two instances in the recent tables by Maruta, Shinohara and Kikui of optimal codes of dimension 5 over F5.
The n-point-invariants of the projective line and cross-ratios of n-tuples