The theorem of Czerniakiewicz and Makar-Limanov, that all the automorphisms of a free algebra of rank two are tame is proved here by showing that the group of these automorphisms is the free product of two groups (amalgamating their intersection), the group of all affine automorphisms and the group of all triangular automorphisms. The method consists in finding a bipolar structure. As a consequence every finite subgroup of automorphisms (in characteristic zero) is shown to be conjugate to a group...

Let $G$ be a finite abelian group with identity element $1_G$ and $L={⨁}_{g\in G}{L}^g$ be an infinite dimensional $G$-homogeneous vector space over a field of characteristic $0$. Let $E=E\left(L\right)$ be the Grassmann algebra generated by $L$. It follows that $E$ is a $G$-graded algebra. Let $\left|G\right|$ be odd, then we prove that in order to describe any ideal of $G$-graded identities of $E$ it is sufficient to deal with $G^{\text{'}}$-grading, where $|G^{\text{'}}|\le |G|$, ${dim}_F{L}^{1_{G^{\text{'}}}}=\infty$ and ${dim}_F{L}^{g^{\text{'}}}<\infty$ if $g^{\text{'}}\ne 1_{G^{\text{'}}}$. In the same spirit of the case $\left|G\right|$ odd, if $\left|G\right|$ is even it is sufficient to study only those $G$-gradings such that...

Recently Umirbaev has proved the long-standing Anick conjecture, that is, there exist wild automorphisms of the free associative algebra $K\langle x,y,z\rangle$ over a field $K$ of characteristic 0. In particular, the well-known Anick automorphism is wild. In this article we obtain a stronger result (the Strong Anick Conjecture that implies the Anick Conjecture). Namely, we prove that there exist wild coordinates of $K\langle x,y,z\rangle$. In particular, the two nontrivial coordinates in the Anick automorphism are both wild. We establish a...

We investigate derived equivalences between subalgebras of some $\Phi$-Auslander-Yoneda algebras from a class of $n$-angles in weakly $n$-angulated categories. The derived equivalences are obtained by transferring subalgebras induced by $n$-angles to endomorphism algebras induced by approximation sequences. Then we extend our constructions in T. Brüstle, S. Y. Pan (2016) to $n$-angle cases. Finally, we give an explicit example to illustrate our result.