Search results for "Projective geometry"
showing 10 items of 51 documents
Dido's problem in the plane for domains with fixed diameter
1994
We find the connected compact domains in the closed half-plane, with fixed area and diameter, which minimize the relative perimeter.
Pieri’s 1898 Geometry of Position Memoir
2021
This chapter contains an English translation of Mario Pieri’s 1898c memoir, The Principles of the Geometry of Position Composed into a Deductive Logical System,1 his most important contribution to the foundations of projective geometry.
Correction to ?partial spreads in finite projective spaces and partial designs?
1976
Maps to Projective Space
2000
One of the main goals of algebraic geometry is to understand the geometry of smooth projective varieties. For instance, given a smooth projective surface X, we can ask a host of questions whose answers might help illuminate its geometry. What kinds of curves does the surface contain? Is it covered by rational curves, that is, curves birationally equivalent to ℙ1? If not, how many rational curves does it contain, and how do they intersect each other? Or is it more natural to think of the surface as a family of elliptic curves (genus-1 Riemann surfaces) or as some other family? Is the surface isomorphic to ℙ2 or some other familiar variety on a dense set? What other surfaces are birationally …
A generalization of Dembowski's theorem on semi-planes
1981
Divisible designs and groups
1992
We study (s, k, λ1, λ2)-translation divisible designs with λ1≠0 in the singular and semi-regular case. Precisely, we describe singular (s, k, λ1, λ2)-TDD's by quasi-partitions of suitable quotient groups or subgroups of their translation groups. For semi-regular (s, k, λ1, λ2)-TDD's (and, more general, for the case λ2>λ1) we prove that their translation groups are either Frobenius groups or p-groups of exponent p. Some examples are given for the singular, semi-regular and regular case.
Sur la r�gularit� de la fonction croissance d'une vari�t� riemannienne
1994
On etudie la differentiabilite de la fonction croissance d'une variete riemannienne complete. En general, elle a la meme regularite qu'une fonction concave: la derivee peut avoir des sauts pour lesquels on donne une formule. Dans le cas analytique reel, la fonction croissance est de classeC1. Un exemple montre qu'elle n'est pas necessairementC2. A titre d'application, nous construisons, pour toute variete ouverte paracompacteM et toute fonction croissantev de classeC1, une metrique continue de croissance egale av et une metrique de classeC∞ surM de croissance proche dev en topologieC1-fine.