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The categories of flows of Set and Top

- Othman Echi
- Mathematics
- 1 June 2012

Abstract Following John Kennison, a flow (or discrete dynamical system) in a category C is a couple ( X , f ) , where X is an object of C and f : X → X is a morphism, called the iterator. If ( A , f… Expand

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KORSELT NUMBERS AND SETS

- K. Bouallegue, Othman Echi, R. Pinch
- Mathematics
- 1 March 2010

Let α ∈ ℤ\{0}. A positive integer N is said to be an α-Korselt number (Kα-number, for short) if N ≠ α and p - α divides N - α for each prime divisor p of N. We are concerned, here, with both a… Expand

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SPECTRAL PRIMAL SPACES

- Othman Echi, Tarek Turki
- Mathematics
- 26 February 2019

Let f : X → X be a mapping. Consider 𝒜(f) = {O ⊆ X : f−1(O) ⊆ O}. Then, according to Echi, 𝒜(f) is an Alexandroff topology. A topological space X is called a primal space if its topology coincides… Expand

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Feuilletages et topologie spectrale

- Ezzeddine Bouacida, Othman Echi, Ezzeddine Salhi
- Mathematics
- 1 April 2000

Let F be a codimension-one foliation, transversally oriented, of class C r …rV0† on a connected closed manifold M. The class of a leaf F of F is de®ned to be the union of all leaves G with FG. Let X… Expand

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An up-spectral space need not be A-spectral

- Othman Echi, Riyadh Gargouri
- Mathematics
- 2004

An A-spectral space is a space such that its one-point compactifi- cation is a spectral space. An up-spectral space is defined to be a topological space X satisfying the axioms of a spectral space… Expand

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ON THE SPECTRALIFICATION OF A HEMISPECTRAL SPACE

- Othman Echi, Mohamed Oueld Abdallahi
- Mathematics
- 1 August 2011

An open subset U of a topological space X is called intersection compact open, or ICO, if for every compact open set Q of X, U ∩ Q is compact. A continuous map f of topological spaces will be called… Expand

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An extension theorem for sober spaces and the Goldman topology

- Ezzeddine Bouacida, Othman Echi, Gabriel Picavet, E. Salhi
- Mathematics
- 2003

Goldman points of a topological space are defined in order to extend the notion of prime G-ideals of a ring. We associate to any topological space a new topology called Goldman topology. For sober… Expand

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The Cardinality of a Sphere Relative to an Edit Distance

- Othman Echi
- 2009

Let Σ be an alphabet (a finite set). We denote by Σ∗ the set consisting of all finite words (or strings) that can be made from the letters (or phonemes). The set of all n-letter words over Σ will be… Expand

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Quasi-homeomorphisms, Goldspectral spaces and Jacspectral spaces

- Othman Echi
- Mathematics
- 2003

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THE KORSELT SET OF pq

- Othman Echi, Nejib Ghanmi
- Mathematics
- 7 April 2012

Let α ∈ ℤ\{0}. A positive integer N is said to be an α-Korselt number (Kα-number, for short) if N ≠ α and N - α is a multiple of p - α for each prime divisor p of N. By the Korselt set of N, we mean… Expand

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