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We prove that all minimal symplectic four-manifolds are essentially irreducible. We also clarify the relationship between holomorphic and symplectic minimality of K\"ahler surfaces. This leads to a new proof of the deformation-invariance of…

Symplectic Geometry · Mathematics 2007-05-23 M. J. D. Hamilton , D. Kotschick

Using the orthogonal connectedness, we introduce the notion of orthogonal decomposability of convex polytopes and study it in the case of Platonic and Archimedean solids. While doing so, we also encounter polytopes which are not…

Combinatorics · Mathematics 2026-03-10 Julia Q. Du , Xuemei He , Xiaotian Song , Daniela Stiller , Liping Yuan , Tudor Zamfirescu

We prove a precise inversion of adjunction formula for the log pair associated to a non-degenerate hypersurface. As a corollary, the minimal log discrepancies of non-degenerate normal hypersurface singularities are bounded from above by…

Algebraic Geometry · Mathematics 2007-05-23 Florin Ambro

We argue that for a smooth surface S, considered as a ramified cover over the projective plane branched over a nodal-cuspidal curve B one could use the structure of the fundamental group of the complement of the branch curve to understand…

Algebraic Geometry · Mathematics 2011-06-29 Michael Friedman , Mina Teicher

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

We prove that a smooth surface, non of general type, in projective four-space, which lies on a quartic hypersurface with isolated singularities has degree at most 27 (in fact we prove a slightly more general result).

Algebraic Geometry · Mathematics 2007-05-23 Ph. Ellia , D. Franco

We study real Lagrangian analytic surfaces in C^2 with a non-degenerate complex tangent. Webster proved that all such surfaces can be transformed into a quadratic surface by formal symplectic transformations of C^2. We show that there is a…

Complex Variables · Mathematics 2009-09-25 Xianghong Gong

We recall two basic conjectures on the developables of convex projective curves, prove one of them and disprove the other in the firdt nontrivial case of curves in RP^3. Namely, we show that i) the tangent developable surface of any convex…

Algebraic Geometry · Mathematics 2007-05-23 V. Sedykh , B. Shapiro

Based on the thermodynamic variation, we rigorously derive the sharp-interface model for solid-state dewetting on a flat substrate in the form of cylindrical symmetry. The governing equations for the model belong to fourth-order geometric…

Materials Science · Physics 2018-05-22 Quan Zhao

We study degenerations of non-simple principally polarized abelian surfaces to the boundary in the toroidal compactification of $\mathcal{A}_2$, and describe the degenerate abelian surfaces as well as the degenerate elliptic curves that…

Algebraic Geometry · Mathematics 2022-07-27 Nelson Alvarado

We prove some restriction theorems for flat homogeneous surfaces of codimension greater than one.

Classical Analysis and ODEs · Mathematics 2007-05-23 Laura DeCarli , Alex Iosevich

We prove necessary and sufficient conditions for a smooth surface in a 4-manifold X to be pseudoholomorphic with respect to some almost complex structure on X. This provides a systematic approach to the construction of pseudoholomorphic…

Differential Geometry · Mathematics 2007-05-23 Christian Bohr

We classify the non-degenerate homogeneous hypersurfaces in real and complex affine four-space whose symmetry group is at least four-dimensional.

Differential Geometry · Mathematics 2007-05-23 Michael Eastwood , Vladimir Ezhov

In this article we study congruences of lines in $\mathbb{P}^n$, and in particular of order one. After giving general results, we obtain a complete classification in the case of $\mathbb{P}^4$ in which the fundamental surface $F$ is in fact…

Algebraic Geometry · Mathematics 2017-02-03 Pietro De Poi

For the genus-$4$ Heegaard surface in the $3$-sphere, we present a sufficient condition for a non-separating weak reducing pair to be separated by a reducing sphere for the surface. As a consequence, we reduce the connectivity problem in…

Geometric Topology · Mathematics 2026-04-20 Sangbum Cho , Yuya Koda , Jung Hoon Lee

We prove sharp local smoothing estimates for curve averages in all dimensions. As a corollary, we prove the sharp $L^p$ boundedness of the helical maximal operator in $\mathbb{R}^4$, which was previously known only for $\mathbb{R}^2$ and…

Classical Analysis and ODEs · Mathematics 2025-07-30 Shengwen Gan , Dominique Maldague , Changkeun Oh

We show that the link cobordism maps defined by the author are graded and satisfy a grading change formula. Using the grading change formula, we prove a new bound for $\Upsilon_K(t)$ for knot cobordisms in negative definite 4-manifolds. As…

Geometric Topology · Mathematics 2018-10-19 Ian Zemke

We give a new criterion for when a resolution of a surface of general type with canonical singularities has big cotangent bundle and a new lower bound for the values of $d$ for which there is a surface with big cotangent bundle that is…

Algebraic Geometry · Mathematics 2019-12-23 Bruno De Oliveira , Michael L Weiss

Using degeneration to scrolls, we give an easy proof of non-existence of curves of low genera on general surfaces in P3 of degree d >=5. We show, along the same lines, boundedness of families of curves of small enough genera on general…

Algebraic Geometry · Mathematics 2011-03-16 Ciro Ciliberto , Mikhail Zaidenberg

Let $X$ be a normal crossing compact complex surface with triple points. We prove that there exists a family of smoothings of $X$ when $X$ satisfies suitable conditions. Since our differential geometric proof also includes the case where…

Differential Geometry · Mathematics 2022-03-15 Naoto Yotsutani