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The noncommutative projective scheme $operatorname{mathsf{Proj_{nc}}} S$ of a $(pm 1)$-skew polynomial algebra $S$ in $n$ variables is considered to be a $(pm 1)$-skew projective space of dimension $n-1$. In this paper, using combinatorial methods, we give a classification theorem for $(pm 1)$-skew projective spaces. Specifically, among other equivalences, we prove that $(pm 1)$-skew projective spaces $operatorname{mathsf{Proj_{nc}}} S$ and $operatorname{mathsf{Proj_{nc}}} S$ are isomorphic if and only if certain graphs associated to $S$ and $S$ are switching (or mutation) equivalent. We also discuss invariants of $(pm 1)$-skew projective spaces from a combinatorial point of view.
We investigate (twisted) rings of differential operators on the resolution of singularities of a particular irreducible component of the (Zarisky) closure of the minimal orbit $bar O_{mathrm{min}}$ of $mathfrak{sp}_{2n}$, intersected with the Borel s
A hypergroup is stringent if $a boxplus b$ is a singleton whenever $a eq -b$. A hyperfield is stringent if the underlying additive hypergroup is. Every doubly distributive skew hyperfield is stringent, but not vice versa. We present a classification
The goal of this paper is to explicitly detect all the arithmetic genera of arithmetically Cohen-Macaulay projective curves with a given degree $d$. It is well-known that the arithmetic genus $g$ of a curve $C$ can be easily deduced from the $h$-vect
We give a geometric classification of complex $n$-dimensional $2$-step nilpotent (all, commutative and anticommutative) algebras. Namely, has been found the number of irreducible components and their dimensions. As a corollary, we have a geometric cl
In this essay we study various notions of projective space (and other schemes) over $mathbb{F}_{1^ell}$, with $mathbb{F}_1$ denoting the field with one element. Our leading motivation is the Hiden Points Principle, which shows a huge deviation betwee