Abstract We give algebraic characterisations of the type I and CCR properties for locally compact second countable, ample Hausdorff groupoids in terms subquotients its Boolean inverse semigroup open local bisections. It yields turn both semigroups with meets their Booleanisation.

We study the locally recoverable codes on algebraic curves. In the first part of this article, we provide a bound of generalized Hamming weight of these codes. Whereas in the second part, we propose a new family of algebraic geometric LRC codes, that are LRC codes from Norm-Trace curve. Finally, using some properties of Hermitian codes, we improve the bounds of distance proposed in [1] for some...

This survey covers a decade and a half of joint work with L. Lehmann, G. M. Mbakop, and L. M. Pardo. We address the problem of finding a smooth algebraic sample point for each connected component of a real algebraic variety, being only interested in components which are generically smooth locally complete intersections. The complexity of our algorithms is essentially polynomial in the degree of...

Globally, the solution set of a system of polynomial equations with complex coefficients can be decomposed into irreducible components. Using numerical algebraic geometry, each irreducible component is represented using a witness set thereby yielding a numerical irreducible decomposition of the solution set. Locally, the irreducible decomposition can be refined to produce a local irreducible de...

The “weak” BSD conjecture predicts that for an elliptic curve E over a number field K, we have rankE(K) = ords=1 L(E/K, s). The miracle of this formula is that it relates two quantities with very different origins: the left hand side is an algebraic object while the right hand side is an analytic object. Furthermore, the algebraic rank is “global” in nature, while the analytic rank can be defin...

Based on the algebraic transformation of a randomly switched linear measurement equation to a nonlinear, yet deterministic equation, an asymptotic observer is constructed for a class of systems encountered in manufacturing, telecommunications, and embedded control applications. The observer is shown to be locally exponentially stable for any arbitrary switching sequence, and combines the algebr...

There are two standard model-theoretic methods for proving the finite model property for modal and superintuionistic logics, the standard filtration and the selective filtration. While the corresponding algebraic descriptions are better understood in modal logic, it is our aim to give similar algebraic descriptions of filtrations for superintuitionistic logics via locally finite reducts of Heyt...

We show that a strong well-based cylindrical algebraic decomposition P of a bounded semi-algebraic set is a regular cell decomposition, in any dimension and independently of the method by which P is constructed. Being well-based is a global condition on P that holds for the output of many widely used algorithms. We also show the same for S of dimension at most 3 and P a strong cylindrical algeb...

Let T be an infinite locally finite tree. We say that T has exactly one end, if in T any two one-way infinite paths have a common rest (infinite subpath). The paper describes the structure of such trees and tries to formalize it by algebraic means, namely by means of acyclic monounary algebras or tree semilattices. In these algebraic structures the homomorpisms and direct products are considere...