4 citations · 7 across the 7 of their papers we have counts for
13 papers · 1 filter
Bivariate quaternionic factorizations and surfaces that decompose into two circles
Johanna Frischauf, Niels Lubbes, Hans-Peter Schröcker
We present an algebraic and geometric condition for bivariate quaternionic polynomials of arbitrary bidegree to have a univariate linear left or right factor. We apply this quatern…
Self-intersections of surfaces that contain two circles through each point
Niels Lubbes
We classify the singular loci of real surfaces in three-space that contain two circles through each point. We characterize how a circle in such a surface meets this loci as it move…
Shapes of surfaces that contain a great and a small circle through each point
Niels Lubbes
We classify the topological types of surfaces in the 3-dimensional unit sphere that contain both a great and a small circle through each point. In particular, these surfaces are ho…
Coupler curves of moving graphs and counting realizations of rigid graphs
Georg Grasegger, Boulos El Hilany, Niels Lubbes
A calligraph is a graph that for almost all edge length assignments moves with one degree of freedom in the plane, if we fix an edge and consider the vertices as revolute joints. T…
Projective isomorphisms between rational surfaces
Bert Jüttler, Niels Lubbes, Josef Schicho
We present a method for computing projective isomorphisms between rational surfaces that are given in terms of their parametrizations. The main idea is to reduce the computation of…
Möbius automorphisms of surfaces with many circles
Niels Lubbes
We classify real two-dimensional orbits of conformal subgroups such that the orbits contain two circular arcs through a point. Such surfaces must be toric and admit a Möbius automo…