To any essential right ideal $I$ in a bounded HNP ring $R$ we may assign a divisor $\partial I$, the image of the finite length module $R/I$ in the Grothendieck group $K_0(\text{fl. mod-}R)$. We show that there is a composition of divisors $\circ$ for which $\partial I J = \partial I \circ \partial J$. Additionally, we describe this composition, and show that $\partial$ is faithful.
Gutierrez Fernandez and Garcia conjectured that every maximal nilpotent linear subspace of $M_n(F)$ contains a matrix of nilindex $n$, and verified this for $n \le 4$. We prove that the conjecture does not hold for $n = 5$ over every field of characteristic zero.
We show that the formal skew Laurent series ring $R = D(\! ( x; \sigma )\! )$ over a commutative Dedekind domain $D$ with an automorphism $\sigma$ is a noncommutative Dedekind domain. If $\sigma$ acts trivially on the ideal class group of $D$, then $K_0(R)$, the Grothendieck group of $R$, is isomorphic to $K_0(D)$. Furthermore, we determine the Krull dimension, the global dimension, the general linear rank, and the stable rank of $R$.
The L'vov-Kaplansky conjecture states that the image of a multilinear noncommutative polynomial $f$ in the matrix algebra $M_n(K)$ is a vector space for every $n \in {\mathbb N}$. We prove this conjecture for the case where $f$ has degree $3$ and $K$ is an algebraically closed field of characteristic $0$.
Let $f(X_1,\dots, X_n)$ be a nonzero multilinear noncommutative polynomial. If $A$ is a unital algebra with a surjective inner derivation, then every element in $A$ can be written as $f(a_1,\dots,a_n)$ for some $a_i\in A$.
Let $F$ be an infinite field and let $f$ be a nonzero multilinear polynomial with coefficients in $F$. We prove that for every positive integer $d$ there exists a positive integer $s$ such that $f(M_{s}(F))$, the image of $f$ in $M_{s}(F)$, contains all trace zero $d \times d$ matrices. In particular, the image of $f$ in the algebra of all finitary matrices contains all trace zero finitary matrices.