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We investigate when the categories of all rational $A$-modules and of finite dimensional rational modules are closed under extensions inside the category of $C^*$-modules, where $C^*$ is the cofinite topological completion of $A$. We give a…

Category Theory · Mathematics 2011-10-13 Miodrag C. Iovanov

We define a closure operation for ideals in a commutative ring which has all the good properties of solid closure (at least in the case of equal characteristic) but such that also every ideal in a regular ring is closed. This gives in…

Commutative Algebra · Mathematics 2007-05-23 Holger Brenner

For a discrete group $G$, we use the natural correspondence between ideals in the Boolean algebra $ \mathcal{P}_G$ of subsets of $G$ and closed subsets in the Stone-$\check{C}$ech compactifi-cation $\beta G$ as a right topological semigroup…

General Topology · Mathematics 2017-04-11 Igor Protasov , Ksenia Protasova

In this paper, we introduce a notion of strongly quasi-local algebras. They are defined for each discrete metric space with bounded geometry, and sit between the Roe algebra and the quasi-local algebra. We show that strongly quasi-local…

Operator Algebras · Mathematics 2021-08-03 Hengda Bao , Xiaoman Chen , Jiawen Zhang

We give a purely algebraic construction of the continuous closure of any finitely generated torsion free module; a concept first studied by H.~Brenner and M.~Hochster. The construction implies that, at least in characteristic 0, taking…

Commutative Algebra · Mathematics 2010-10-27 János Kollár

We prove that the cohomology groups of an etale Q_p-local system on a smooth proper rigid analytic space are finite-dimensional Q_p-vector spaces, provided that the base field is either a finite extension of Q_p or an algebraically closed…

Number Theory · Mathematics 2016-11-22 Kiran S. Kedlaya , Ruochuan Liu

We investigate the connection between measure and capacity for the space of nonempty closed subsets of {0,1}*. For any computable measure, a computable capacity T may be defined by letting T(Q) be the measure of the family of closed sets…

Logic in Computer Science · Computer Science 2010-06-03 Douglas Cenzer , Paul Brodhead

We present the notions of positively complete theory and general forms of amalgamation in the framework of positive logic. We explore the fundamental properties of positively complete theories and study the behaviour of companion theories…

Logic · Mathematics 2019-11-15 Mohammed Belkasmi

We prove that strongly homotopy algebras (such as $A_\infty$, $C_\infty$, sh Lie, $B_\infty$, $G_\infty$,...) are homotopically invariant in the category of chain complexes. An important consequence is a rigorous proof that `strongly…

Algebraic Topology · Mathematics 2007-05-23 Martin Markl

We construct an abelian category A(G) of sheaves over a category of closed subgroups of the r-torus G and show it is of finite injective dimension. It can be used as a model for rational $G$-spectra in the sense that there is a homology…

Algebraic Topology · Mathematics 2007-05-23 J. P. C. Greenlees

The topological interpretation of modal logics provides descriptive languages and proof systems for reasoning about points of topological spaces. Recent work has been devoted to model checking of spatial logics on discrete spatial…

Logic in Computer Science · Computer Science 2020-05-13 Vincenzo Ciancia , Diego Latella , Mieke Massink , Erik de Vink

We show that for the standard map family, for all values of the parameter, except one, the mapping has positive topological entropy. The main tool is the following result. Let $S$ be a compact connected orientable surface and $f:S…

Dynamical Systems · Mathematics 2024-05-28 Fernando Oliveira

''Positive geometries'' are a class of semi-algebraic domains which admit a unique ''canonical form'': a logarithmic form whose residues match the boundary structure of the domain. The study of such geometries is motivated by recent…

Algebraic Geometry · Mathematics 2025-09-11 Francis Brown , Clément Dupont

Let $\mathbb{H}\trianglelefteq\mathbb{G}$ be a closed normal subgroup of a locally compact quantum group. We introduce a strictly positive group-like element affiliated with $L^{\infty}(\mathbb{G})$ that, roughly, measures the failure of…

Operator Algebras · Mathematics 2022-01-27 Alexandru Chirvasitu

We characterize the boundaries of positive holomorphic chains (with both compact and non-compact support) in an arbitrary complex manifold. We then consider a compact oriented real submanifold of dimension 2p-1 in a compact Kahler manifold…

Complex Variables · Mathematics 2017-12-12 F. Reese Harvey , H. Blaine Lawson

Let H be a separable, infinite dimensional Hilbert space and let S be a countable subset of H. Then most positive operators on H have the property that every nonzero vector in the span of S is cyclic, in the sense that the set of operators…

Functional Analysis · Mathematics 2007-05-23 Nik Weaver

For any site of definition $\mathcal C$ of a Grothendieck topos $\mathcal E$, we define a notion of a $\mathcal C$-ary Lawvere theory $\tau: \mathscr C \to \mathscr T$ whose category of models is a stack over $\mathcal E$. Our definitions…

Category Theory · Mathematics 2019-08-12 Boaz Haberman

We study coherent systems of type $(n,d,n+1)$ on a Petri curve $X$ of genus $g\ge2$. We describe the geometry of the moduli space of such coherent systems for large values of the parameter $\alpha$. We determine the top critical value of…

Algebraic Geometry · Mathematics 2007-12-14 U. N. Bhosle , L. Brambila-Paz , P. E. Newstead

In this paper, we prove that: For any given finitely many distinct points $P_1,...,P_r$ and a closed subvariety $S$ of codimension $\geq 2$ in a complete toric variety over a uncountable (characteristic 0) algebraically closed field, there…

Algebraic Geometry · Mathematics 2009-05-12 Yifei Chen , Vyacheslav Shokurov

In this paper, we investigate the well-posedness and positivity property of infinite-dimensional linear system with unbounded input and output operators. In particular, we characterize the internal and external positivity for this class of…

Optimization and Control · Mathematics 2023-10-12 Yassine El Gantouh