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Motivated by Cuntz-Krieger-Toeplitz systems associated to undirected graphs and representations of groupoids, we obtain a generalisation of the Sz-Nagy's Dilation Theorem for operator valued partially positive semidefinite maps on…

Operator Algebras · Mathematics 2025-11-04 Aurelian Gheondea , Bogdan Udrea

We study $\textrm{Sym}(\infty)$-orbit closures of not necessarily closed points in the Zariski spectrum of the infinite polynomial ring $\mathbb{C}[x_{ij}:\, i\in\mathbb{N},\,j\in[n]]$. Among others, we characterize invariant prime ideals…

Algebraic Geometry · Mathematics 2026-01-30 Mario Kummer , Cordian Riener

The paper deals with Henselian valued field with analytic structure. Actually, we are focused on separated analytic structures, but the results remain valid for strictly convergent analytic ones as well. A classical example of the latter is…

Algebraic Geometry · Mathematics 2018-11-29 Krzysztof Jan Nowak

For the class of differentiable maps of the plane and, in particular, for standard-like maps (McMillan form), a simple relation is shown between the directions of the local invariant manifolds of a generic point and its contribution to the…

Mathematical Physics · Physics 2015-02-25 Matteo Sala , Roberto Artuso

We characterize completey (give a necessary and suffcient condition using special neat embeddings)for a relation algebra to belong to the amalgamation, strong amalgamation, and superamalgamation base of the class of representable algebras.…

Logic · Mathematics 2013-04-03 Tarek Sayed Ahmed

We study the model theoretic strength of various lattices that occur naturally in topology, like closed (semi-linear or semi-algebraic or convex) sets. The method is based on weak monadic second order logic and sharpens previous results by…

Logic · Mathematics 2018-07-26 Marcus Tressl

We produce a criterion for open sets in projective $n$-space over a separably closed field to have \'etale cohomological dimension bounded by $2n-3$. We use the criterion to exhibit a scheme for which \'etale cohomological dimension is…

Commutative Algebra · Mathematics 2010-12-01 Manoj Kummini , Uli Walther

It is shown that for positive real numbers $ 0<\lambda_{1}<\dots<\lambda_{n}$, $\left[\frac{1}{\beta({\lambda_i}, {\lambda_j})}\right]$, where $ \beta(\cdot,\cdot)$ denotes the beta function, is infinitely divisible and totally positive.…

Functional Analysis · Mathematics 2020-05-05 Priyanka Grover , Veer Singh Panwar , A Satyanarayana Reddy

We show that Pleba\'nski's equation for self-dual metrics is equivalent to a pair of equations describing canonical transformations in 2-dimensional phase spaces. Examples of linearizations of these equations are given.

General Relativity and Quantum Cosmology · Physics 2007-05-23 J. Tafel

Two subanalytic subsets of R^n are called s-equivalent at a common point P if the Hausdorff distance between their intersections with the sphere centered at P of radius r vanishes of order greater than s when r tends to 0. In this paper we…

Algebraic Geometry · Mathematics 2012-09-17 Massimo Ferrarotti , Elisabetta Fortuna , Leslie Wilson

Every finite dimensional real representation of a compact real semisimple Lie algebra determines a metric 2-step nilpotent Lie algebra and a corresponding simply connected metric 2-step nilpotent Lie group N. We study the differential…

Differential Geometry · Mathematics 2008-06-18 Patrick Eberlein

We give a geometric characterization of self-extremal sets in $L_p(\Om)$ spaces that partially extends our previous results to the case of $L_p$\ spaces.

Metric Geometry · Mathematics 2007-05-23 V. Nguyen-Khac , K. Nguyen-Van

Given a pseudo-effective divisor L we construct the diminished ideal of L, a "continuous" extension of the asymptotic multiplier ideal for big divisors to the pseudo-effective boundary. For most pseudo-effective divisors L the multiplier…

Algebraic Geometry · Mathematics 2013-06-13 Brian Lehmann

Partially ordered sets (posets) play a universal role as an abstract structure in many areas of mathematics. For finite posets, an explicit enumeration of distinct partial orders on a set of unlabelled elements is known only up to a…

Combinatorics · Mathematics 2025-04-15 Christoph Minz

We prove the Zariski dense orbit conjecture in positive characteristic for regular self-maps of split semiabelian varieties.

Number Theory · Mathematics 2021-08-17 Dragos Ghioca , Sina Saleh

We introduce a new sphericalization mapping for metric spaces that is applicable in very general situations, including totally disconnected fractal type sets. For an unbounded complete metric space which is uniformly perfect at a base point…

Functional Analysis · Mathematics 2026-05-01 Anders Björn , Jana Björn , Riikka Korte , Sari Rogovin , Timo Takala

We give an explicit upper bound for the algebraic degree and an explicit lower bound for the absolute value of the minimum of a polynomial function on a compact connected component of a basic closed semialgebraic set when this minimum is…

Algebraic Geometry · Mathematics 2011-12-05 Gabriela Jeronimo , Daniel Perrucci , Elias Tsigaridas

We give a characterization of extremal sets in Hilbert spaces that generalizes a classical theorem of H. W. E. Jung. We investigate also the behaviour of points near to the circumsphere of such a set with respect to the Kuratowski and…

Metric Geometry · Mathematics 2007-05-23 V. NguyenKhac , K. NguyenVan

We say that an inclusion of an algebra $A$ into a $C^*$-algebra $B$ has the ideal separation property if closed ideals in $B$ can be recovered by their intersection with $A$. Such inclusions have attractive properties from the point of view…

Operator Algebras · Mathematics 2025-03-05 Are Austad , Hannes Thiel

We give new positive and negative results (some conditional) on speeding up computational algebraic geometry over the reals: (1) A new and sharper upper bound on the number of connected components of a semialgebraic set. Our bound is novel…

Algebraic Geometry · Mathematics 2007-05-23 J. Maurice Rojas