5 problems

A unit circulant digraph of order $n$ is a Cayley digraph ${\rm Cay}({\mathbb Z}_n,S)$, where $S\subseteq{\mathbb Z}_n^*$ is the set of units in ${\mathbb Z}_n$. Toida's conjecture…

A twisted Hilbert space is a twisted sum of two copies of the Hilbert space $\ell_2$, and it is self-similar when it is isomorphic to each of its infinite-dimensional closed subspa…

BCI-to-CI conjecture. Every BCI-group is a CI-group.

For any $k\geq 1$, let $\operatorname{op}(l)$, $\odot$, and $\operatorname{op}(r)$ be the three symbols used to form constraints in the tidy parallel $k$-signaletic operads. For a…

For each $k\geq 1$, consider the four $k$-signaletic operads introduced in the paper: tidy or messy, and parallel or series. An isomorphism is understood in the category of operads…