Nizar El Idrissi

activity

20212026

collaborators

12 papers

math.FA2026

Coarse comparison of Bessel families

Nizar El Idrissi

We classify Bessel families in separable Hilbert spaces under coarse equivalence relations: $f$ and $f ~$ are equivalent if the seminorms $∥ T_{f} \cdot ∥$ and $\|T_{\tilde f}\…

math.CT2026

Comparison categories: the normal form and the regularity of comparison data

Nizar El Idrissi

Many equivalence relations of mathematics (Green's relations on a semigroup, orbit relations of group actions, conjugacy) are defined by transforming a morphism on its two sides. W…

math.CT2026

A general equivalence relation on the global class of morphisms of a category

Nizar El Idrissi

We introduce a general equivalence relation on the global class of morphisms of a category that subsumes several classical notions of equivalence in mathematics. We show that group…

math.CA2026

Two Hornich-Hlawka-type and Gram matrix-based inequalities

Nizar El Idrissi, Hicham Zoubeir

We establish two inequalities in real inner product spaces. The first is a multiplicative strengthening of the classical Hornich-Hlawka inequality: for all vectors $x, y, z$ in a rea…

math.FA2025

Probability measure annihilating all finite-dimensional subspaces

Nizar El Idrissi, Hicham Zoubeir

We propose in this short note a prime numbers-based method for constructing probability measures on infinite-dimensional Banach spaces annihilating all finite-dimensional subspaces…

math.FA2025

Almost sure linear independence of absolutely continuous Hilbert space-valued random vectors with respect to a special class of Hilbert space probability measures

Nizar El Idrissi, Hicham Zoubeir

This note examines the implications of randomly selecting vectors from an infinite-dimensional Hilbert space on linear independence, assuming that for all $k$ , the first $k$ vector…

math.DS2022

Functions with a maximal number of finite invariant or internally-1-quasi-invariant sets or supersets

Nizar El Idrissi, Samir Kabbaj

A relaxation of the notion of invariant set, known as $k$ -quasi-invariant set, has appeared several times in the literature in relation to group dynamics. The results obtained in t…

math.GN2022

Path-connectedness of the intersection of translates of St(n,H)

Nizar El Idrissi, Samir Kabbaj, Brahim Moalige

If $H$ is a Hilbert space, the Stiefel manifold $S t (n, H)$ is formed by all the independent $n$ -tuples in $H$ . In this article, we contribute to the topological study of Stiefel man…

math.FA2021

Independence, infinite dimension, and operators

Nizar El Idrissi, Samir Kabbaj

In [Appl. Comput. Harmon. Anal., 46(3):664-673, 2019], O. Christensen and M. Hasannasab observed that assuming the existence of an operator $T$ sending $e_{n}$ to $e_{n + 1}$ for all $…

math.FA2021

Frames generated by the functional calculus and function frames of a normal operator

Nizar El Idrissi

In this article, we prove that sequences generated by the functional calculus $(f (T) (e_{n}))_{n \in N}$ can be equivalently written as function sequences $(f_n(T) g)_{n \in…

math.FA2021

Intersections of translates of finite-dimensionally valued frame spaces are conditionally slice-full and almost slice-full

Nizar El Idrissi

In recent work, the topology of frame spaces $F_{(X, μ), n}$ has been studied via Stiefel manifolds, revealing in particular a connectedness property for intersections of t…

math.FA2021

Path-connectedness and topological closure of some sets related to the non-compact Stiefel manifold

Nizar El Idrissi, Samir Kabbaj, Brahim Moalige

If $H$ is a Hilbert space, the non-compact Stiefel manifold $S t (n, H)$ consists of independent $n$ -tuples in $H$ . In this article, we contribute to the topological study of non-comp…