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Let $G$ be a linear algebraic group over an infinite field $k$. Loosely speaking, a $G$-torsor over $k$-variety is said to be versal if it specializes to every $G$-torsor over any $k$-field. The existence of versal torsors is well-known. We…

Algebraic Geometry · Mathematics 2023-07-14 Uriya A. First

Motivated by properties of higher tangent lifts of geometric structures, we introduce concepts of weighted structures for various geometric objects on a manifold F equipped with a homogeneity structure. The latter is a smooth action on F of…

Differential Geometry · Mathematics 2024-11-04 Janusz Grabowski , Katarzyna Grabowska , Zohreh Ravanpak

A rational vector field on a complex projective smooth surface $S$ is said to be birationally integrable if it generates, by integration, a one-parameter subgroup of the group $\operatorname{Bir}(S)$ of birational transformations of $S$. We…

Algebraic Geometry · Mathematics 2025-09-26 David Marín , Marcel Nicolau

We give two characterizations of cones over ellipsoids in real normed vector spaces. Let $C$ be a closed convex cone with nonempty interior such that $C$ has a bounded section of codimension $1$. We show that $C$ is a cone over an ellipsoid…

Functional Analysis · Mathematics 2015-01-30 Farhad Jafari , Tyrrell B. McAllister

A subset of vertices of a graph is minimal if, within all subsets of the same size, its vertex boundary is minimal. We give a complete, geometric characterization of minimal sets for the planar integer lattice X. Our characterization…

Combinatorics · Mathematics 2020-09-28 Radhika Gupta , Ivan Levcovitz , Alexander Margolis , Emily Stark

We characterize embedded $\C^1$ hypersurfaces of $\R^n$ as the only locally closed sets with continuously varying flat tangent cones whose measure-theoretic-multiplicity is at most $m<3/2$. It follows then that any (topological)…

Algebraic Geometry · Mathematics 2013-09-17 Mohammad Ghomi , Ralph Howard

Factors $\frac{X}{Y}$ in a free group $F$ with $Y$ normal in $X$ are considered. Precise results on the free structure of ${Y}$ relative to the free structure of ${X}$ when $\frac{X}{Y}$ is abelian are obtained. Some extensions and…

Group Theory · Mathematics 2009-07-14 Ted Hurley

We classify canonical algebras such that for every dimension vector of a regular module the corresponding module variety is normal (respectively, a complete intersection). We also prove that for the dimension vectors of regular modules…

Representation Theory · Mathematics 2009-09-29 Grzegorz Bobinski

The paper addresses the question whether a random functional, a map from a set $E$ into the space of real-valued measurable functions on a probability space, has a measurable version with values in ${\mathbb R}^E$. Similarly, one may ask…

Functional Analysis · Mathematics 2024-02-08 Michael Oberguggenberger

We consider a uniform $r$-bundle $E$ on a complex rational homogeneous space $X$ %over complex number field $\mathbb{C}$ and show that if $E$ is poly-uniform with respect to all the special families of lines and the rank $r$ is less than or…

Algebraic Geometry · Mathematics 2020-07-15 Rong Du , Xinyi Fang , Yun Gao

John Roe \cite{Roe lectures} introduced coarse structures for arbitrary sets $X$ by considering subsets of $X\times X$. That definition, while natural for analysts, is a bit more difficult to digest for topologists and geometers. In this…

Metric Geometry · Mathematics 2007-05-23 J. Dydak , C. S. Hoffland

We study the behaviour of analytic torsion under smooth fibrations. Namely, let F \to E \to^{f} B be a smooth fiber bundle of connected closed oriented smooth manifolds and let $V$ be a flat vector bundle over $E$. Assume that $E$ and $B$…

dg-ga · Mathematics 2018-11-28 Wolfgang Lueck , Thomas Schick , Thomas Thielmann

We study ample stable vector bundles on minimal rational surfaces. We give a complete classification of those moduli spaces for which the general stable bundle is both ample and globally generated. We also prove that if $V$ is any stable…

Algebraic Geometry · Mathematics 2021-07-22 Jack Huizenga , John Kopper

Let $\mathbf{TB}$ be the category of totally bounded, locally compact metric spaces with the $C_0$ coarse structures. We show that if $X$ and $Y$ are in $\mathbf{TB}$ then $X$ and $Y$ are coarsely equivalent if and only if their Higson…

General Topology · Mathematics 2019-08-15 Kotaro Mine , Atsushi Yamashita

We prove that any complete surface with constant mean curvature in a homogeneous space E(\kappa,\tau) which is transversal to the vertical Killing vector field is, in fact, a vertical graph. As a consequence we get that any orientable,…

Differential Geometry · Mathematics 2015-03-02 José M. Manzano , M. Magdalena Rodríguez

Consider a BV function on a Riemannian manifold. What is its differential? And what about the Hessian of a convex function? These questions have clear answers in terms of (co)vector/matrix valued measures if the manifold is the Euclidean…

Functional Analysis · Mathematics 2022-07-01 Camillo Brena , Nicola Gigli

It is shown that the description of certain class of representations of the holonomy Lie algebra associated to hyperplane arrangement $\Delta$ is essentially equivalent to the classification of $\vee$-systems associated to $\Delta.$ The…

Representation Theory · Mathematics 2017-04-17 M. V. Feigin , A. P. Veselov

We characterize the Archimedean vector lattices that admit a positively homogeneous continuous function calculus by showing that the following two conditions are equivalent for each $n$-tuple $\boldsymbol{x} = (x_1,\ldots,x_n)\in X^n$,…

Functional Analysis · Mathematics 2019-01-23 Niels Jakob Laustsen , Vladimir G. Troitsky

Let $\mathbb{F}$ be a field of characteristic different from $2$ and $3$, and let $V$ be a vector space of dimension $2$ over $\mathbb{F}$. The generic classification of homogeneous quadratic maps $f\colon V\to V$ under the action of the…

Representation Theory · Mathematics 2022-09-27 R. Durán Díaz , L. Hernández Encinas , J. Muñoz Masqué

Roughly speaking, functional analysis is the study of vector spaces of arbitrary dimension over the field of real or complex numbers, and the continuous linear mappings between such spaces. Naturally, the notion of continuity requires a…

Functional Analysis · Mathematics 2025-10-09 Christoph Bock