3 problems

Classification conjecture. There are only two full-dimensional thick te-interlaces, up to resigning or permuting rows and columns:

For matrices $A$ and $B$ of size $m\times n$, say that they are congruent if there are invertible square matrices $U$ and $V$ of orders $m$ and $n$, respectively, such that $UA=BV$…

Let $F_7$ be the Fourier matrix of order $7$, and let $P_7^q$ denote the displayed Petrescu family, with $q\in\mathbb T$. A regular complex Hadamard matrix is one whose row scalar…