Let $S$ be a unital associative ring and $S[t;σ,δ]$ be a skew polynomial ring, where $σ$ is an injective endomorphism of $S$ and $δ$ a left $σ$-derivation. For each $f\in S[t;σ,δ]$ of degree $m>1$ with a unit as leading coefficient, we construct a unital nonassociative algebra whose behaviour reflects the properties of $f$. The algebras obtained yield canonical examples of right division algebras when $f$ is irreducible. We investigate the structure of these algebras. The structure of their right nucleus depends on the choice of $f$. In the classical literature, this nucleus appears as the eigenspace of $f$, and is used to investigate the irreducible factors of $f$. We give necessary and sufficient criteria for skew polynomials of low degree to be irreducible.
We describe families of nonassociative finite unital rings that occur as quotients of natural nonassociative orders in generalized nonassociative cyclic division algebras over number fields. These natural orders have already been used to systematically construct fully diverse fast-decodable space-time block codes. We show how the quotients of natural orders can be employed for coset coding. Previous results by Oggier and Sethuraman involving quotients of orders in associative cyclic division algebras are obtained as special cases.
Let $S$ be a unital ring, $S[t;σ,δ]$ a skew polynomial ring where $σ$ is an injective endomorphism and $δ$ a left $σ$-derivation, and suppose $f\in S[t;σ,δ]$ has degree $m$ and an invertible leading coefficient. Using right division by $f$ to define the multiplication, we obtain unital nonassociative algebras $S_f$ on the set of skew polynomials in $S[t;σ,δ]$ of degree less than $m$. We study the structure of these algebras. When $S$ is a Galois ring and $f$ base irreducible, these algebras yield families of finite unital nonassociative rings $A$, whose set of (left or right) zero divisors has…
We define a nonassociative generalization of cyclic Azumaya algebras employing skew polynomial rings $D[t;σ]$, where $D$ is an Azumaya algebra of constant rank with center $C$ and $σ$ an automorphism of $D$, such that $σ|_{C}$ has finite order. The automorphisms of these algebras are canonically induced by ring automorphisms of the skew polynomial ring $D[t;σ]$ used in their construction. We achieve a description of their inner automorphisms. Results on the automorphisms of classical Azumaya algebras and central simple algebras of this type are obtained as special cases.
In this thesis, we study the properties of a nonassociative algebra construction from skew polynomial rings. This construction was introduced by Petit in the 1960s but largely ignored until recently. In particular, the automorphism groups of these algebras are studied, paying particular attention to the case when the construction yields a finite semifield. The thesis is concluded by revisiting a result on associative solvable crossed product algebras by both Petit and Albert. We show a crossed product algebra is solvable if and only if it can be written as a chain of Petit algebras satisfying …
Let $K$ be a field and $σ$ an automorphism of $K$ of order $n$.Employing a nonassociative algebra, we study the eigenspace of a bounded skew polynomial $f\in K[t;σ]$. We mainly treat the case that $K/F$ is a cyclic field extension of degree $n$ with Galois group generated by $σ$. We obtain lower bounds on the dimension of the eigenspace, and compute it in special cases as a quotient algebra. Conditions under which a monic polynomial $f\in F[t]\subset K[t;σ]$ is reducible are obtained in special cases.
We solve the noncommutative Noether's problem for the reflection groups by showing that the skew field of the invariants of the Weyl algebra under the action of any reection group is a Weyl field, that is isomorphic to a skew field of some Weyl algebra over a transcendental extension of the ground field. We also extend this result to the invariants of the ring of differential operators on any dimensional torus.The results are applied to obtain analogs of the Gelfand-Kirillov Conjecture for Cherednik algebras and Galois algebras.
Let $D$ be a finite-dimensional division algebra over its center and $R=D[t;σ,δ]$ a skew polynomial ring. Under certain assumptions on $δ$ and $σ$, the ring of central quotients $D(t;σ,δ) = \{f/g \,|\, f \in D[t;σ,δ], g \in C(D[t;σ,δ])\}$ of $D[t;σ,δ]$ is a central simple algebra with reduced norm $N$. We calculate the norm $N(f)$ for some skew polynomials $f\in R$ and investigate when and how the reducibility of $N(f)$ reflects the reducibility of $f$.
We provide a formula for commputing the discriminant of skew Calabi-Yau algebra over a central Calabi-Yau algebra. This method is applied to study the Jacobian and discriminant for reflection Hopf algebras.
We show how cyclic $(f,σ,δ)$-codes over finite rings canonically induce a $\mathbb{Z}$-lattice in $\mathbb{R}^N$ by using certain quotients of orders in nonassociative division algebras defined using the skew polynomial $f$. This construction generalizes the one using certain $σ$-constacyclic codes by Ducoat and Oggier, which used quotients of orders in non-commutative associative division algebras defined by $f$, and can be viewed as a generalization of the classical Construction A for lattices from linear codes. It has the potential to be applied to coset coding, in particular to wire-tap co…
We use ring-theoretic methods and methods from the theory of skew braces to produce set-theoretic solutions to the reflection equation. We also use set-theoretic solutions to construct solutions to the parameter-dependent reflection equation.
Let $D$ be division algebra over its center $C$, let $σ$ be an endormorphism of $D$, let $δ$ be a left $σ$-derivation of $D$, and let $R=D[t;σ,δ]$ be a skew polynomial ring. We study the structure of a class of nonassociative algebras, denoted by $S_f$, whose construction canonically generalises that of the associative quotient algebras $R/Rf$ where $f\in R$ is right-invariant. We determine the structure of the right nucleus of $S_f$ when the polynomial $f$ is bounded and not right invariant and either $δ= 0$, or $σ= {\rm id}_D$. As a by-product, we obtain a new proof on the size of the right …
We are interested in the McKay quiver $Γ(G)$ and skew group rings $A*G$, where $G$ is a finite subgroup of $\mathrm{GL}(V)$, where $V$ is a finite dimensional vector space over a field $K$, and $A$ is a $K-G$-algebra. These skew group rings appear in Auslander's version of the McKay correspondence. In the first part of this paper we consider complex reflection groups $G \subseteq \mathrm{GL}(V)$ and find a combinatorial method, making use of Young diagrams, to construct the McKay quivers for the groups $G(r,p,n)$. We first look at the case $G(1,1,n)$, which is isomorphic to the symmetric group…
We investigate deformations of skew group algebras arising from the action of the symmetric group on polynomial rings over fields of arbitrary characteristic. Over the real or complex numbers, Lusztig's graded affine Hecke algebra and analogs are all isomorphic to Drinfeld Hecke algebras, which include the symplectic reflection algebras and rational Cherednik algebras. Over fields of prime characteristic, new deformations arise that capture both a disruption of the group action and also a disruption of the commutativity relations defining the polynomial ring. We classify deformations for the s…
Drinfeld orbifold algebras deform skew group algebras in polynomial degree at most one and hence encompass graded Hecke algebras, and in particular symplectic reflection algebras and rational Cherednik algebras. We introduce parametrized families of Drinfeld orbifold algebras for symmetric groups acting on doubled representations that generalize rational Cherednik algebras by deforming in degree one. We characterize rich families of maps recording commutator relations with their linear parts supported only on and only off the identity when the symmetric group acts on the natural permutation re…
