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The central structure in various versions of noncommutative geometry is a differential calculus on an associative algebra. This is an analogue of the calculus of differential forms on a manifold. In this short review we collect examples of…

High Energy Physics - Theory · Physics 2008-02-03 F. M"uller-Hoissen

An $r$-skeleton on a compact space is a family of continuous retractions having certain rich properties. The $r$-skeletons have been used to characterized the Valdivia compact spaces and the Corson compact spaces. Here, we characterized a…

General Topology · Mathematics 2018-04-06 S. Garcia-Ferreira , C. Yescas-Aparicio

In some previous work, we defined an invariant of genus zero nonabelian Hodge spaces taking the form of a diagram. Here, enriching the diagram by fission data to obtain a refined invariant, the enriched tree, including a partition of the…

Algebraic Geometry · Mathematics 2026-03-24 Jean Douçot

We give examples of $n$-sequentially compact spaces that are not $(n+1)$-sequentially compact under several assumptions. We improve results from Kubis and Szeptycki by building such examples from $\mathfrak{b=c}$ and…

General Topology · Mathematics 2023-05-02 César Corral , Osvaldo Guzmán , Carlos López-Callejas

The purpose of this paper is to show that wormholes in noncommutative geometry can be macroscopic, based in part on an earlier study. The necessary violation of the weak energy condition is attributable to the noncommutative-geometry…

General Relativity and Quantum Cosmology · Physics 2013-12-25 Peter K. F. Kuhfittig

We construct six- and four-dimensional toroidal compactifications of the Type I string with magnetic flux on the D-branes. The open strings in this background probe a noncommutative internal geometry. Phenomenologically appealing features…

High Energy Physics - Theory · Physics 2009-10-31 Ralph Blumenhagen , Lars Goerlich , Boris Kors , Dieter Lust

The purely mathematical root of the dequantization constructions is the quest for a sheafification needed for presheaves on a noncommutative space. The moment space is constructed as a commutative space, approximating the noncommutative…

Mathematical Physics · Physics 2007-05-23 Freddy Van Oystaeyen

We review some recent results and conjectures saying that, roughly speaking, periodic cyclic homology of a smooth non-commutative algebraic variety should carry all the additional "motivic" structures possessed by the usual de Rham…

Algebraic Geometry · Mathematics 2010-03-17 D. Kaledin

The non-commutative algebraic analog of the moduli of vector and covector fields is built. The structure of moduli of derivations of non-commutative algebras are studied. The canonical coupling is introduced and the conditions for…

q-alg · Mathematics 2008-02-03 G. N. Parfionov , R. R. Zapatrin

We present an exposition of contractive spaces and of relatively contractive maps. Contractive spaces are the natural opposite of measure-preserving actions and relatively contractive maps the natural opposite of relatively…

Dynamical Systems · Mathematics 2016-03-29 Darren Creutz

The purpose of this short note was to outline the current status, then in 2011, of some research programs aiming at a categorification of parts of A.Connes' non-commutative geometry and to provide an outlook on some possible subsequent…

Operator Algebras · Mathematics 2015-06-22 Paolo Bertozzini , Roberto Conti , Wicharn Lewkeeratiyutkul

The subject of the present work is the de Rham part of non-commutative Hodge structures on the periodic cyclic homology of differential graded algebras and categories. We discuss explicit formulas for the corresponding connection on the…

Algebraic Geometry · Mathematics 2012-07-25 D. Shklyarov

In this paper we introduce a family of examples that can be regarded as spaces of nonpositive curvature, but with the distinct quality that they are not complete as metric spaces. This amounts to the fact that they are modelled on a finite…

Metric Geometry · Mathematics 2009-08-27 Cristian Conde , Gabriel Larotonda

Evolutionary relationships between species are represented by phylogenetic trees, but these relationships are subject to uncertainty due to the random nature of evolution. A geometry for the space of phylogenetic trees is necessary in order…

Statistics Theory · Mathematics 2022-09-21 Jonas Lueg , Maryam K. Garba , Tom M. W. Nye , Stephan F. Huckemann

In this survey article we discuss a framework of noncommutative geometry with differential graded categories as models for spaces. We outline a construction of the category of noncommutative spaces and also include a discussion on…

Algebraic Geometry · Mathematics 2017-04-04 Snigdhayan Mahanta

We construct a new compactification of the moduli space of maps from pointed nonsingular projective stable curves to a nonsingular projective variety with prescribed ramification indices at the points. It is shown to be a proper…

Algebraic Geometry · Mathematics 2011-06-01 Bumsig Kim , Andrew Kresch , Yong-Geun Oh

In this investigation, we introduce the class of non-archimedean frames in spirit with the topological notion of non-archimedean spaces. We explore various properties of these frames - particularly their spaciality. We attach a base that…

General Topology · Mathematics 2025-09-16 Francisco Ávila , Miriam Bocardo-Gaspar , Julio Urenda , Angel Zaldívar

Periodic trees are combinatorial structures which are in bijection with cluster tilting objects in cluster categories of affine type $\tilde{A}_{n-1}$. The internal edges of the tree encode the $c$-vectors corresponding to the cluster…

Representation Theory · Mathematics 2014-07-03 Kiyoshi Igusa , Gordana Todorov , Jerzy Weyman

We study noncommutative generalizations of such notions of the classical symplectic geometry as degenerate Poisson structure, Poisson submanifold and quotient manifold, symplectic foliation and symplectic leaf for associative Poisson…

Symplectic Geometry · Mathematics 2007-05-23 Zakaria Giunashvili

We prove compactness and hence existence for solutions to a class of non linear transport equations. The corresponding models combine the features of linear transport equations and scalar conservation laws. We introduce a new method which…

Analysis of PDEs · Mathematics 2011-08-22 Fethi Ben Belgacem , Pierre-Emmanuel Jabin