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We consider Shimura varieties associated to a unitary group of signature $(n-1, 1)$. For these varieties, we construct $p$-adic integral models over odd primes $p$ which ramify in the imaginary quadratic field with level subgroup at $p$…

Number Theory · Mathematics 2025-07-08 Ioannis Zachos , Zhihao Zhao

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

For an isolated hypersurface singularity which is neither simple nor simple elliptic, it is shown that there exists a distinguished basis of vanishing cycles which contains two basis elements with an arbitrary intersection number. This…

Algebraic Geometry · Mathematics 2017-06-13 Wolfgang Ebeling

We classify curvature homogeneous hypersurfaces in S^4 and H^4. In higher dimesnsion one only has the FKM examples and an isolate one by Tsukada of a hypersurface in H^5. Besides some simple examples, we show that there exists an isolated…

Differential Geometry · Mathematics 2025-05-13 Robert Bryant , Luis Florit , Wolfgang Ziller

We introduce new biholomorphic invariants for real-analytic hypersurfaces in 2-dimensional complex space and show how they can be used to show that a hypersurface possesses few automorphisms. We give conditions, in terms of the new…

Complex Variables · Mathematics 2007-05-23 P. Ebenfelt , B. Lamel , D. Zaitsev

Explicit formulas determining the dimension and the degree of the singular subscheme of hypersurfaces in ${\mathbb P}^n$ are given in terms of the graded Betti numbers of the minimal free resolution of the corresponding Jacobian algebra.…

Algebraic Geometry · Mathematics 2026-05-05 Alexandru Dimca , Gabriel Sticlaru

We consider the topology for a class of hypersurfaces with highly nonisolated singularites which arise as exceptional orbit varieties of a special class of prehomogeneous vector spaces, which are representations of linear algebraic groups…

Algebraic Geometry · Mathematics 2015-12-31 James Damon

An intriguing correspondence between four-qubit systems and simple singularity of type $D_4$ is established. We first consider an algebraic variety $X$ of separable states within the projective Hilbert space…

Mathematical Physics · Physics 2015-06-18 Frédéric Holweck , Jean-Gabriel Luque , Michel Planat

We compare several different methods involving Hodge-theoretic spectra of singularities which produce constraints on the number and type of isolated singularities on projective hypersurfaces of fixed degree. In particular, we introduce a…

Algebraic Geometry · Mathematics 2024-02-01 B. Castor

We find sharp upper bounds on the order of the automorphism group of a hypersurface in complex projective space in every dimension and degree. In each case, we prove that the hypersurface realizing the upper bound is unique up to…

Algebraic Geometry · Mathematics 2024-11-28 Louis Esser , Jennifer Li

By using superisolated surface singularities whose link is a rational homology sphere we give counterexamples to some of the most important conjetures concernig invariants of normal surface singularities.

Algebraic Geometry · Mathematics 2007-05-23 I. Luengo-Velasco , A. Melle-Hernandez , A. Nemethi

We establish existence of functorial orbifold reductions of singularities for Poisson subvarieties in smooth Poisson threefolds. Namely, we show that with enough weighted blowups, one can reduce the singularities of such Poisson…

Algebraic Geometry · Mathematics 2026-04-21 Simon Lapointe , Mykola Matviichuk , Brent Pym , Boris Zupancic

In this article we study rational curves with a unique unibranch genus-$g$ singularity, which is of {\it $\ka$-hyperelliptic} type in the sense of \cite{To}; we focus on the cases $\ka=0$ and $\ka=1$, in which the semigroup associated to…

Algebraic Geometry · Mathematics 2017-08-29 Ethan Cotterill , Lia Feital , Renato Vidal Martins

A Q-homology plane is a normal complex algebraic surface having trivial rational homology. We classify singular Q-homology planes which are C^1- or C*-ruled. We analyze their completions, the number of different rulings, the number of…

Algebraic Geometry · Mathematics 2014-02-21 Karol Palka

It is well known that the exceptional set in a resolution of a rational surface singularity is a tree of rational curves. We generalize the combinatoric part of this statement to higher dimensions and show that the highest cohomologies of…

Algebraic Geometry · Mathematics 2009-04-22 D. A. Stepanov

We describe singularities of distance squared functions on singular surfaces in $\mathbb{R}^3$ parameterized by smooth map-germs $\mathcal{A}$-equivalent to one of $S_k$, $B_k$, $C_k$ and $F_4$ singularities in terms of extended geometric…

Differential Geometry · Mathematics 2024-08-02 Toshizumi Fukui , Masaru Hasegawa

We study the geometry of homogeneous hypersurfaces and their focal sets in complex hyperbolic spaces. In particular, we provide a characterization of the focal set in terms of its second fundamental form and determine the principal…

Differential Geometry · Mathematics 2007-05-23 Jurgen Berndt , Jose Carlos Diaz-Ramos

We consider a hypersurface in $\mathbb{C}^n$ with an isolated singular point at the origin, and study the mixed Hodge structure of the stalk of its intersection cohomology complex at the origin. In particular we express the dimension of…

Algebraic Geometry · Mathematics 2017-02-13 Takahiro Saito

Let X be a singular real rational surface obtained from a smooth real rational surface by performing weighted blow-ups. Denote by Aut(X) the group of algebraic automorphisms of X into itself. Let n be a natural integer and let…

Algebraic Geometry · Mathematics 2010-04-08 Johannes Huisman , Frédéric Mangolte

This paper investigates the stratification of the discriminant hypersurface associated with a univariate polynomial via the number of its distinct complex roots. We introduce two novel approaches different from the one based on…

Algebraic Geometry · Mathematics 2025-10-01 Rizeng Chen , Hoon Hong , Jing Yang