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This article shows that every non-isotropic harmonic 2-torus in complex projective space factors through a generalised Jacobi variety related to the spectral curve. Each map is composed of a homomorphism into the variety and a rational map…

Differential Geometry · Mathematics 2007-05-23 Ian McIntosh

We show that geometric disorder leads to purely singular continuous spectrum generically. The main input is a result of Simon known as the ``Wonderland theorem''. Here, we provide an alternative approach and actually a slight strengthening…

Mathematical Physics · Physics 2007-05-23 Daniel Lenz , Peter Stollmann

We construct a quasi-coherent sheaf of associative algebras which controls a category of $AV$-modules over a smooth quasi-projective variety. We establish a local structure theorem, proving that in \'etale charts these associative algebras…

Representation Theory · Mathematics 2026-02-02 Yuly Billig , Colin Ingalls

We present a geometric approach to defining an algebra $\hat{\mathcal G}(M)$ (the Colombeau algebra) of generalized functions on a smooth manifold $M$ containing the space ${\mathcal D}'(M)$ of distributions on $M$. Based on differential…

Functional Analysis · Mathematics 2007-05-23 Michael Grosser , Michael Kunzinger , Roland Steinbauer , James Vickers

In this paper we study the action of the fundamental group of a finite metric graph on its universal covering tree. We assume the graph is finite, connected and the degree of each vertex is at least three. Further, we assume an…

Dynamical Systems · Mathematics 2016-07-01 George Kenison , Richard Sharp

A survey is given of the work on strong regularity for uniform algebras over the last thirty years, and some new results are proved, including the following. Let A be a uniform algebra on a compact space X and let E be the set of all those…

Functional Analysis · Mathematics 2007-05-23 J. F. Feinstein , D. W. B. Somerset

We show that for any fixed dense graph G and bounded-degree tree T on the same number of vertices, a modest random perturbation of G will typically contain a copy of T . This combines the viewpoints of the well-studied problems of embedding…

Combinatorics · Mathematics 2025-05-30 Michael Krivelevich , Matthew Kwan , Benny Sudakov

We show that, if A is a separable simple unital C*-algebra which absorbs the Jiang-Su algebra Z tensorially and which has real rank zero and finite decomposition rank, then A is tracially AF in the sense of Lin, without any restriction on…

Operator Algebras · Mathematics 2007-05-23 Wilhelm Winter

A generalized $t$-pyramid is a graph obtained from a certain kind of tree (a subdivided star or a subdivided cubic caterpillar) and the line graph of a subdivided cubic caterpillar by identifying simplicial vertices. We prove that for every…

Combinatorics · Mathematics 2025-04-04 Tara Abrishami , Bogdan Alecu , Maria Chudnovsky , Sepehr Hajebi , Sophie Spirkl

Given a class of graphs F, we say that a graph G is universal for F, or F-universal, if every H in F is contained in G as a subgraph. The construction of sparse universal graphs for various families F has received a considerable amount of…

Combinatorics · Mathematics 2011-08-24 Daniel Johannsen , Michael Krivelevich , Wojciech Samotij

We investigate the algebraic genericity of various families of continuous functions exhibiting extreme irregularity, focusing on fractal dimensions, H\"older regularity, and fractional differentiability. Our first main result shows that for…

Functional Analysis · Mathematics 2026-02-20 Céline Esser , Saeid Maghsoudi , Daniel L. Rodríguez-Vidanes , Juan. B. Seoane-Sepúlveda

We show that we can approximate every function $f\in C^{k}(\bar{B_1})$ with a $s$-harmonic function in $B_1$ that vanishes outside a compact set. That is, $s$-harmonic functions are dense in $C^{k}_{\rm{loc}}$. This result is clearly in…

Analysis of PDEs · Mathematics 2015-03-17 Serena Dipierro , Ovidiu Savin , Enrico Valdinoci

We prove that given a fixed finite tree $P$, almost all trees contain $P$ as a subtree. Moreover, the inclusion can be made so that it induces an embedding of the corresponding (quantum) automorphism groups, thereby providing generic…

Operator Algebras · Mathematics 2026-05-20 Lucas Alger , Julie Capron , Félix de la Salle

For every well founded tree $\mathcal{T}$ having a unique root such that every non-maximal node of it has countable infinitely many immediate successors, we construct a $\mathcal{L}_\infty$-space $X_{\mathcal{T}}$. We prove that for each…

Functional Analysis · Mathematics 2016-08-08 Pavlos Motakis , Daniele Puglisi , Despoina Zisimopoulou

We prove various results connecting structural or algebraic properties of graphs and groups to conditions on their spaces of harmonic functions. In particular: we show that a group with a finitely supported symmetric measure has a…

Group Theory · Mathematics 2016-09-22 Matthew Tointon

In arXiv:math/0603621 we introduced the notion of a partial translation $C^*$-algebra for a discrete metric space. Here we demonstrate that several important classical $C^*$-algebras and extensions arise naturally by considering partial…

Operator Algebras · Mathematics 2008-04-04 J. Brodzki , G. A. Niblo , N. J. Wright

In this article, we prove two results. First, we construct a dense subset in the space of polynomial foliations of degree $n$ such that each foliation from this subset has a leaf with at least $\frac{(n+1)(n+2)}2-4$ handles. Next, we prove…

Complex Variables · Mathematics 2018-04-13 Nataliya Goncharuk , Yury Kudryashov

We study an abstract notion of tree structure which lies at the common core of various tree-like discrete structures commonly used in combinatorics: trees in graphs, order trees, nested subsets of a set, tree-decompositions of graphs and…

Combinatorics · Mathematics 2017-02-28 Reinhard Diestel

Quasi-trees generalize trees in that the unique "path" between two nodes may be infinite and have any countable order type. They are used to define the rank-width of a countable graph in such a way that it is equal to the least upper-bound…

Logic in Computer Science · Computer Science 2023-06-22 Bruno Courcelle

In this paper we consider a random partition of the plane into cells, the partition being based on the nodes and links of a {\it random planar geometric graph}. The resulting structure generalises the \emph{random \tes}\ hitherto studied in…

Probability · Mathematics 2016-06-07 Richard Cowan , Albert K. L. Tsang