On \(L^ 2\) and \(L^ 3\)
type: Item
instance of: scholarly article
title: On \(L^ 2\) and \(L^ 3\)
zbMATH Open document ID: 0705.53006
author: Graciela S. Birman
published in: Elemente der Mathematik
publication date: 1988-01-01T00:00:00Z
full work available at URL: https://eudml.org/doc/141423
review text: Two results are proposed: a) A closed convex curve in the Minkowski 2- space has at least four light-like tangents. b) A curve in Minkowski 3- space having light-like tangents everywhere must be (a piece of) a straight line. [Reviewer's remark: The first result is true for any closed smooth curve in the Minkowski plane and very easy to see. In contrast to the statement of the author it does not provide a suitable analogon of the four-vertex- theorem, because for closed convex curves in the Minkowski plane the existence of four extrema of the curvature can be shown though it is not defined everywhere. The second proposition is wrong.].
Mathematics Subject Classification ID: 53A04
zbMATH DE Number: 4157402
zbMATH Keywords: closed curves in Lorentzian space
reviewed by: Bernd Wegner
MaRDI profile type: Publication
description: scientific article; zbMATH DE number 4157402