arXiv subjects

Pablo Mazón

Publications and source records attributed to Pablo Mazón.

4 recordsLinked to original sources

arXiv2026

Trivariate Splines on Fans of Hyperplane Arrangements and Koszul Homology

We study the space of splines $\mathcal{S}^{\mathbf{r}}(Σ^\mathscr{A})$ where ${\mathbf{r}}$ denotes a smoothness distribution and $Σ^\mathscr{A}$ is the fan of a central hyperplane arrangement $\mathscr{A}$ in $\mathbb{R}^3$. This is the first step in the analysis of splines on three-dimensional cross-cut partitions, which naturally generalize planar cross-cut partitions. We show that the Hilbert function of $\mathcal{S}^{\mathbf{r}}(Σ^\mathscr{A})$ is bounded by an expression that involves the dimensions of specific Koszul homology modules constructed from the defining equations of the hyperplane arrangement $\mathscr{A}$ and the smoothness distribution function. By exploiting this connection with Koszul homology, we are able to: 1) compute the dimension of the spline space in high degrees, 2) compute all values of the dimension of the spline space if $\mathscr{A}$ is generic with five or fewer hyperplanes, and 3) compute the Hilbert function of the spline space if $\mathscr{A}$ is a generic arrangement with sufficiently many hyperplanes and ${\mathbf{r}}$ is a constant distribution. As an application of our methods, we compute $\dim \mathcal{S}^0_d(Σ^\mathscr{A})$ and $\dim \mathcal{S}^1_d(Σ^\mathscr{A})$ for all values of $d$ when $\mathscr{A}$ is a generic arrangement.

math.CO↗

arXiv2026

Real Line Congruences of Trilinear Birational Maps

Trilinear mappings appear naturally when performing spatial isogeometric discretizations of degree $p = 1$. Among them, birational maps are characterized by the property that both the mapping and the associated inverse map are rational and thus easy to evaluate. These mappings have recently been analyzed, and a classification over the field of complex numbers has been obtained. The parameter lines of trilinear mappings form three two-parameter families of straight lines, and thus it is promising to analyze these mappings with the tools provided by the field of line geometry, which is a classical branch of higher geometry. Indeed, in the birational case, the three families of lines form space-filling line congruences associated with rational mappings that can be used to parameterize certain algebraic surfaces. Moreover, the three systems are closely related. In this paper, we present a classification, over the field of real numbers, of the parametric line congruences arising from trilinear birational maps.

math.AG↗

arXiv2026

Explicit Inversion of Planar NURBS Curves

We prove that a general planar NURBS curve parametrization $ϕ: [u_0,u_m] \xrightarrow{} C \subset \mathbb{R}^2$ admits an inverse map $ϕ^{-1}: C \xrightarrow{} [u_0,u_m]$ defined by rational splines. More specifically, we construct a family of rational spline functions on the curve $C$, present explicit formulas for their computation, and prove that the inverse parametrization admits a representation as a linear combination of these functions. Several examples are provided to illustrate the effectiveness of the proposed approach.

cs.GR↗

arXiv2025

Construction of birational trilinear volumes via tensor rank criteria

We provide effective methods to construct and manipulate trilinear birational maps $ϕ:(\mathbb{P}^1)^3\dashrightarrow \mathbb{P}^3$ by establishing a novel connection between birationality and tensor rank. These yield four families of nonlinear birational transformations between 3D spaces that can be operated with enough flexibility for applications in computer-aided geometric design. More precisely, we describe the geometric constraints on the defining control points of the map that are necessary for birationality, and present constructions for such configurations. For adequately constrained control points, we prove that birationality is achieved if and only if a certain $2\times 2\times 2$ tensor has rank one. As a corollary, we prove that the locus of weights that ensure birationality is $\mathbb{P}^1\times\mathbb{P}^1\times\mathbb{P}^1$. Additionally, we provide formulas for the inverse $ϕ^{-1}$ as well as the explicit defining equations of the irreducible components of the base loci. Finally, we introduce a notion of "distance to birationality" for trilinear rational maps, and explain how to continuously deform birational maps.

math.AG↗