A. Boussairi

activity

20162024

collaborators

6 papers

math.CO2024

Quasi-orthogonal extension of symmetric matrices

Abderrahim Boussaïri, Brahim Chergui, Zaineb Sarir +1

An $n \times n$ real matrix $Q$ is quasi-orthogonal if $Q^{⊤} Q = q I_{n}$ for some positive real number $q$ . If $M$ is a principal sub-matrix of a quasi-orthogonal matrix $Q$ , we sa…

math.CO2024

Quasi-orthogonal extension of skew-symmetric matrices

Abderrahim Boussaïri, Brahim Chergui, Zaineb Sarir +1

A real matrix $Q$ is quasi-orthogonal if $Q^{⊤} Q = q I$ , for some positive real number $q$ . We prove that any $n \times n$ skew-symmetric matrix $S$ is a principal sub-matrix of a s…

math.CO2020

Critical 3-hypergraphs (detailed version)

Abderrahim Boussairi, Brahim Chergui, Pierre Ille +1

Given a 3-hypergraph $H$ , a subset $M$ of $V (H)$ is a module of $H$ if for each $e \in E (H)$ such that $e \cap M \neq = \emptyset$ and $e ∖ M \neq = \emptyset$ , there exists $m \in M$ …

math.CO2019

On the spectral reconstruction problem for digraphs

Edward Bankoussou-mabiala, Abderrahim Boussaïri, Abdelhak Chaïchaâ +2

The idiosyncratic polynomial of a graph $G$ with adjacency matrix $A$ is the characteristic polynomial of the matrix $A + y (J - A - I)$ , where $I$ is the identity matrix and $J$ is th…

math.CO2018

An exact extremal result for tournaments and 4-uniform hypergraphs

Wiam Belkouche, Abderrahim Boussaïri, Soufiane Lakhlifi +1

In this paper, we address the following problem due to Frankl and Füredi (1984). What is the maximum number of hyperedges in an $r$ -uniform hypergraph with $n$ vertices, such that…

math.CO2016

A transformation that preserves principal minors of skew-symmetric matrices

Abderrahim Boussaïri, Brahim Chergui

Our motivation comes from the work of Engel and Schneider (1980). Their main theorem implies that two symmetric matrices have equal corresponding principal minors of all orders if…