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We present algorithms for reconstructing, up to unavoidable projective automorphisms, surfaces with ordinary singularities in three dimensional space starting from their silhouette, or "apparent contour" - namely the branching locus of a…

Algebraic Geometry · Mathematics 2021-04-26 Matteo Gallet , Niels Lubbes , Josef Schicho , Jan Vršek

In this paper we study the deformation and Q-Gorenstein deformation theory of schemes with non-isolated singularities. We obtain obstruction spaces for the existence of deformations and also for local deformations to exist globally. Finally…

Algebraic Geometry · Mathematics 2009-08-24 Nikolaos Tziolas

We construct a collection of higher Chow cycles on certain surfaces which degenerate to an arrangement of planes in general position. When its degree is 4, this construction gives a new explicit proof of the Hodge-D-Conjecture for a certain…

Algebraic Geometry · Mathematics 2021-06-08 Tokio Sasaki

We consider a surface that admits a $\mathbb{Q}$-Gorenstein degeneration to a cyclic quotient singularity $\frac{1}{dn^2}(1,dna-1)$. Under several technical assumptions, we construct $d$ exceptional vector bundles of rank $n$ which are…

Algebraic Geometry · Mathematics 2020-05-21 Yonghwa Cho

Consider a smooth projective curve and a given embedding into projective space via a sufficiently positive line bundle. We can form the secant variety of $k$-planes through the curve. These are singular varieties, with each secant variety…

Algebraic Geometry · Mathematics 2024-10-15 Daniel Brogan

This paper studies the dynamics of mean curvature flow as it approaches a cylindrical singularity. We proved that the rescaled mean curvature flow converging to a smooth generalized cylinder can be written as a graph over the cylinder in a…

Differential Geometry · Mathematics 2025-08-27 Ao Sun , Jinxin Xue

Inspired by Bondal's conjecture, we study the behavior of exceptional sequences of line bundles on rational C*-surfaces under homogeneous degenerations. In particular, we provide a sufficient criterion for such a sequence to remain…

Algebraic Geometry · Mathematics 2018-01-17 Andreas Hochenegger , Nathan Owen Ilten

This is the paper as published. The topology of a complex plane curve singularity with real branches is deduced from any real deformation having delta crossings. An example of the computation of the global geometric monodromy of a…

alg-geom · Mathematics 2007-05-23 Norbert A'Campo

We investigate geometric properties of surfaces given by certain formulae. In particular, we calculate the singular curvature and the limiting normal curvature of such surfaces along the set of singular points consisting of singular points…

Differential Geometry · Mathematics 2020-03-25 Yoshiki Matsushita , Takuya Nakashima , Keisuke Teramoto

The concept of a normal surface in a triangulated, compact 3-manifold was generalised by Thurston to a spun-normal surface in a non-compact 3-manifold with ideal triangulation. This paper defines a boundary curve map which takes a…

Geometric Topology · Mathematics 2007-06-12 Stephan Tillmann

Motivated by DeVleming's work on moduli of surfaces in $\mathbb{P}^3$ and Chen-Hu-Jiang's work on moduli of threefolds with volume $2$ and geometric genus $4$, we study the deformation of pairs of $\mathbb{P}^3$ and hypersurfaces using the…

Algebraic Geometry · Mathematics 2026-04-30 Jungkai Chen , Yongnam Lee , Phin-Sing Soo

We classify normal stable surfaces with $K_X^2 = 1$, $p_g = 2$ and $q=0$ with a unique singular point which is a non-canonical T-singularity, thus exhibiting two divisors in the main component and a new irreducible component of the moduli…

Algebraic Geometry · Mathematics 2020-12-11 Marco Franciosi , Rita Pardini , Julie Rana , Sönke Rollenske

We prove that finite area isolated singularities of surfaces with constant positive curvature in R^3 are removable singularities, branch points or immersed conical singularities. We describe the space of immersed conical singularities of…

Differential Geometry · Mathematics 2010-07-16 Jose A. Galvez , Laurent Hauswirth , Pablo Mira

We study in this work flat surfaces with conical singularities, that is, surfaces provided with a flat structure with conical singular points. Finding good parameters for these surfaces in the general case is an open question. We give an…

Metric Geometry · Mathematics 2010-11-23 Ousama Malouf

All varieties, extremal contractions, singularities are divided on exceptional and non-exceptional ones. Roughly speaking, there are the infinite families of non-exceptional varieties, extremal contractions or singularities and only the…

Algebraic Geometry · Mathematics 2015-06-26 S. A. Kudryavtsev

We study the geometry of surfaces in $\mathbb{R}^{4}$ with corank $1$ singularities. For such surfaces the singularities are isolated and at each point we define the curvature parabola in the normal space. This curve codifies all the second…

Differential Geometry · Mathematics 2019-09-17 Pedro Benedini Riul , Raúl Oset Sinha , Maria Aparecida Soares Ruas

For curves singularities the dimension of smoothing components in the deformation space is an invariant of the singularity, but in general the deformation space has components of different dimensions. We are interested in the question what…

Algebraic Geometry · Mathematics 2025-04-02 Jan Stevens

The quotient singularities of dimensions two and three obtained from polyhedral groups and the corresponding binary polyhedral groups admit natural resolutions of singularities as Hilbert schemes of regular orbits whose exceptional fibres…

Algebraic Geometry · Mathematics 2007-05-23 Samuel Boissiere , Alessandra Sarti

We prove that if a contact 3-manifold admits an open book decomposition of genus 0, a certain intersection pattern cannot appear in the homology of any of its minimal symplectic fillings, and moreover, fillings cannot contain symplectic…

Symplectic Geometry · Mathematics 2020-05-01 Paolo Ghiggini , Marco Golla , Olga Plamenevskaya

We consider resolution of singularities for $1$-foliations on varieties of dimension at most three in positive characteristic. We prove that such singularities can be completely resolved if we allow tame regular Deligne--Mumford stacks as…

Algebraic Geometry · Mathematics 2025-08-12 Quentin Posva