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We define a general concept of pseudo algebras over theories and 2-theories. A more restrictive such notion was introduced by Hu and Kriz, but as noticed by M. Gould, did not capture the desired examples. The approach taken in this paper…

Category Theory · Mathematics 2008-04-27 Thomas M. Fiore , Po Hu , Igor Kriz

We prove several exact quantitative versions of Helly's and Tverberg's theorems, which guarantee that a finite family of convex sets in $R^d$ has a large intersection. Our results characterize conditions that are sufficient for the…

Combinatorics · Mathematics 2020-05-05 Sherry Sarkar , Alexander Xue , Pablo Soberón

We study cubical sets without degeneracies, which we call square sets. These sets arise naturally in a number of settings and they have a beautiful intrinsic geometry; in particular a square set C has an infinite family of associated square…

Algebraic Topology · Mathematics 2007-05-23 Roger Fenn , Colin Rourke , Brian Sanderson

Polytopes are the basic finite data structures for convex sets: they appear as feasible regions in linear optimization, as geometric summaries in algorithms, and as random objects in stochastic geometry. A natural geometric question is…

Metric Geometry · Mathematics 2026-03-10 Steven Hoehner

A polyhedral map is called $\{p, q\}$-equivelar if each face has $p$ edges and each vertex belongs to $q$ faces. In 1983, it was shown that there exist infinitely many geometrically realizable $\{p, q\}$-equivelar polyhedral maps if $q > p…

Geometric Topology · Mathematics 2007-05-23 Basudeb Datta

Let X and Y be finite dimensional normed spaces, F(X,Y) a collection of all mappings from X into Y. A mapping $P\in F(X,Y)$ is said to be piecewise affine if there exists a finite family of convex polyhedral subsets covering X and such that…

Functional Analysis · Mathematics 2011-11-08 V. V. Gorokhovik

For a closure space (P,f) with f(\emptyset)=\emptyset, the closures of open subsets of P, called the regular closed subsets, form an ortholattice Reg(P,f), extending the poset Clop(P,f) of all clopen subsets. If (P,f) is a finite convex…

Combinatorics · Mathematics 2013-07-08 Luigi Santocanale , Friedrich Wehrung

Let $X$ be a finite set. A family $P$ of subsets of $X$ is called a convex geometry with ground set $X$ if (1) $\emptyset, X\in P$; (2) $A\cap B\in P$ whenever $A,B\in P$; and (3) if $A\in P$ and $A\neq X$, there is an element $\alpha\in…

Combinatorics · Mathematics 2024-01-10 Kolja Knauer , William T. Trotter

Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently for their applications in fields such as nanoscience, granular and colloidal matter, and biology. In all these fields, particle…

Soft Condensed Matter · Physics 2014-03-10 Elizabeth R. Chen , Daphne Klotsa , Michael Engel , Pablo F. Damasceno , Sharon C. Glotzer

We explore several families of flip-graphs, all related to polygons or punctured polygons. In particular, we consider the topological flip-graphs of once-punctured polygons which, in turn, contain all possible geometric flip-graphs of…

Combinatorics · Mathematics 2018-09-10 Hugo Parlier , Lionel Pournin

Deciding whether the union of two convex polyhedra is itself a convex polyhedron is a basic problem in polyhedral computations; having important applications in the field of constrained control and in the synthesis, analysis, verification…

Computational Geometry · Computer Science 2009-08-10 Roberto Bagnara , Patricia M. Hill , Enea Zaffanella

A convex set with nonempty interior is maximal lattice-free if it is inclusion-maximal with respect to the property of not containing integer points in its interior. Maximal lattice-free convex sets are known to be polyhedra. The precision…

Optimization and Control · Mathematics 2011-03-28 Gennadiy Averkov , Christian Wagner , Robert Weismantel

The faces of a convex set owe their relevance to an interplay between convexity and topology that is systematically studied in the work of Rockafellar. Infinite-dimensional convex sets are excluded from this theory as their relative…

Metric Geometry · Mathematics 2026-01-01 Stephan Weis

Very recently Richter and Rogers proved that any convex geometry can be represented by a family of convex polygons in the plane. We shall generalize their construction and obtain a wide variety of convex shapes for representing convex…

Combinatorics · Mathematics 2017-01-13 J. Kincses

Convex sets arising in a variety of applications are well-defined for every relevant dimension. Examples include the simplex and the spectraplex that correspond to probability distributions and to quantum states; combinatorial polytopes and…

Optimization and Control · Mathematics 2025-10-24 Eitan Levin , Venkat Chandrasekaran

We use the cylindrical homomorphism and a geometric construction introduced by J. Lewis to study the Lawson homology groups of certain hypersurfaces $X\subset \mathbb{P}^{n+1}$ of degree $d\leq n+1$. As an application, we compute the…

Algebraic Geometry · Mathematics 2009-04-23 Mircea Voineagu

This article introduces the theory of Veronese polytopes, a broad generalisation of cyclic polytopes. These arise as convex hulls of points on curves with one or more connected components, obtained as the image of the rational normal curve…

Combinatorics · Mathematics 2024-11-22 Marie-Charlotte Brandenburg , Roland Púček

Convex geometry has recently attracted great attention as a framework to formulate general probabilistic theories. In this framework, convex sets and affine maps represent the state spaces of physical systems and the possible dynamics,…

Geometric Topology · Mathematics 2015-06-10 Gen Kimura , Koji Nuida

Evenly convex sets in a topological vector space are defined as the intersection of a family of open half spaces. We introduce a generalization of this concept in the conditional framework and provide a generalized version of the bipolar…

Probability · Mathematics 2012-09-06 Marco Frittelli , Marco Maggis

This article studies a large, general class of orthogonal polytopes which we may call "generic orthotopes". These objects emerged from a desire to represent a Coxeter complex by an orthogonal polytope that is particularly nice with respect…

Combinatorics · Mathematics 2022-10-24 David Richter