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Leonid Makar-Limanov

Publications and source records attributed to Leonid Makar-Limanov.

18 recordsLinked to original sources
arXiv2023

Automorphisms of Veronese subalgebras of polynomial algebras and free Poisson algebras

The Veronese subalgebra $A_0$ of degree $d\geq 2$ of the polynomial algebra $A=K[x_1,x_2,\ldots,x_n]$ over a field $K$ in the variables $x_1,x_2,\ldots,x_n$ is the subalgebra of $A$ generated by all monomials of degree $d$ and the Veronese subalgebra $P_0$ of degree $d\geq 2$ of the free Poisson algebra $P=P\langle x_1,x_2,\ldots,x_n\rangle$ is the subalgebra spanned by all homogeneous elements of degree $kd$, where $k\geq 0$. If $n\geq 2$ then every derivation and every locally nilpotent derivation of $A_0$ and $P_0$ over a field $K$ of characteristic zero is induced by a derivation and a locally nilpotent derivation of $A$ and $P$, respectively. Moreover, we prove that every automorphism of $A_0$ and $P_0$ over a field $K$ closed with respect to taking all $d$-roots of elements is induced by an automorphism of $A$ and $P$, respectively.

math.RA↗
arXiv2021

On the Newton polytope of a Jacobian pair

The Newton polytope related to a ``minimal" counterexample to the Jacobian conjecture is introduced and described. This description allows to obtain a sharper estimate for the geometric degree of the polynomial mapping given by a Jacobian pair and to give a new proof of the Abhyankar's two characteristic pair case.

math.AG↗
arXiv2019

Locally Nilpotent Derivations of Free Algebra of Rank Two

In commutative algebra, if $δ$ is a locally nilpotent derivation of the polynomial algebra $K[x_1,\ldots,x_d]$ over a field $K$ of characteristic 0 and $w$ is a nonzero element of the kernel of $δ$, then $Δ=wδ$ is also a locally nilpotent derivation with the same kernel as $δ$. In this paper we prove that the locally nilpotent derivation $Δ$ of the free associative algebra $K\langle X,Y\rangle$ is determined up to a multiplicative constant by its kernel. We show also that the kernel of $Δ$ is a free associative algebra and give an explicit set of its free generators.

math.RA↗
arXiv2012

Free Poisson fields and their automorphisms

Let $k$ be an arbitrary field of characteristic 0. We prove that the group of automorphisms of a free Poisson field $P(x,y)$ in two variables $x,y$ over $k$ is isomorphic to the Cremona group $\mathrm{Cr}_2(k)$. We also prove that the universal enveloping algebra $P(x_1,...,x_n)^e$ of a free Poisson field $P(x_1,...,x_n)$ is a free ideal ring and give a characterization of the Poisson dependence of two elements of $P(x_1,...,x_n)$ via universal derivatives.

math.RA↗
arXiv2011

The Freiheitssatz for Novikov algebras

We prove the Freiheitssatz for Novikov algebras in characteristic zero. It is also proved that the variety of Novikov algebras is generated by a Novikov algebra on the space of polynomials $k[x]$ in a single variable $x$ over a field $k$ with respect to the multiplication $f\circ g=\partial(f)g$. It follows that the base rank of the variety of Novikov algebras equals 1.

math.RA↗
arXiv2010

A conjecture of Bavula on homomorphisms of the Weyl algebra

In the paper {\em The inversion formulae for automorphisms of polynomial algebras and differential operators in prime characteristic}, J. Pure Appl. Algebra 212 (2008), no. 10, 2320-2337, see also arXiv:math/0604477, Vladimir Bavula states the following Conjecture: (BC) Any endomorphism of a Weyl algebra (in a finite characteristic case) is a monomorphism. The purpose of this preprint is to prove BC for $A_1$, show that BC is wrong for $A_n$ when $n > 1$, and prove an analogue of $BC$ for symplectic Poisson algebras.

math.RA↗
arXiv2010

The Freiheitssatz for Poisson algebras

We prove the Freiheitssatz for Poisson algebras in characteristic zero. We also give a proof of the tameness of automorphisms for two generated free Poisson algebras and prove that an analogue of the commutator test theorem is equivalent to the two dimensional classical Jacobian conjecture using the Freiheitssatz and Jung's Theorem.

math.RA↗
arXiv2008

The Freiheitssatz and the automorphisms of free right-symmetric algebras

We prove the Freiheitssatz for right-symmetric algebras and the decidability of the word problem for right-symmetric algebras with a single defining relation. We also prove that two generated subalgebras of free right-symmetric algebras are free and automorphisms of two generated free right-symmetric algebras are tame.

math.RA↗
arXiv2008

The Conjecture of Nowicki on Weitzenboeck derivations of polynomial algebras

The Weitzenboeck theorem states that the algebra of constants of a linear locally nilpotent derivation of the polynomial algebra K[Z]=K[z_1,...,z_m] in m variables over a field K of characteristic 0 is finitely generated. If m=2n and the Jordan normal form of the derivation consists of Jordan cells of size 2 only, we may assume that K[Z]=K[X,Y] and the derivation sends y_i to x_i and x_i to 0, i=1,...,n. Nowicki conjectured that the algebra of constants of this derivation is generated by x_1,...,x_n and x_iy_j-x_jy_i, i<j. Recently this conjecture was confirmed in the Ph.D. thesis of Khoury, and also by Derksen. In this paper we give an elementary proof of the conjecture of Nowicki. Then we find a very simple system of defining relations of the algebra of constants which corresponds to the reduced Groebner basis of the related ideal with respect to a suitable admissible order, and present an explicit basis of the algebra of constants as a vector space.

math.AC↗
arXiv2008

Automorphisms of elliptic Poisson algebras

We describe the automorphism groups of elliptic Poisson algebras on polynomial algebras in three variables and give an explicit set of generators and defining relations for this group.

math.RA↗
arXiv2004

On the rigidity of small domains

Let $K$ be an algebraically closed field of arbitrary characteristic. Let $A$ be an affine domain over $K$ with transcendence degree 1 which is not isomorphic to $K[x]$, and let $B$ be a domain over $K$. We show that the AK invariant distributes over the tensor product of $A$ by $B$. As a consequence, we obtain a generalization of the cancellation theorem of S. Abhyankar, P. Eakin, and W. Heinzer.

math.AC↗
arXiv2003

The Stable Equivalence and Cancellation Problems

Let $K$ be an arbitrary field of characteristic 0, and $\Aff^n$ the $n$-dimensional affine space over $K$. A well-known cancellation problem asks, given two algebraic varieties $V_1, V_2 \subseteq \Aff^n$ with isomorphic cylinders $V_1 \times \Aff^1$ and $V_2 \times \Aff^1$, whether $V_1$ and $V_2$ themselves are isomorphic. In this paper, we focus on a related problem: given two varieties with equivalent (under an automorphism of $\Aff^{n+1}$) cylinders $V_1 \times \Aff^1$ and $V_2 \times \Aff^1$, are $V_1$ and $V_2$ equivalent under an automorphism of $\Aff^n$? We call this stable equivalence problem. We show that the answer is positive for any two curves $V_1, V_2 \subseteq \Aff^2$. For an arbitrary $n \ge 2$, we consider a special, arguably the most important, case of both problems, where one of the varieties is a hyperplane. We show that a positive solution of the stable equivalence problem in this case implies a positive solution of the cancellation problem.

math.AG↗
arXiv2000

Affine surfaces with $AK(S)=\Bbb C.$

In this paper we give a description of hypersurfaces with trivial ring $AK(S)$, introduced by the second author as following. Let $X$ be an affine variety and let $G(X)$ be the group generated by all $\Bbb {C}^+$-actions on $X$. Then $AK(X)$ is the subring of all regular $G(X)-$ invariant functions on $X.$ We show that a smooth affine surface $S$ with $AK(S)=\Bbb C$ is quasihomogeneous and so may be obtained from a smooth rational projective surface by deleting a divisor of special form, which is called a ``zigzag''. We denote by $A$ the set of all such surfaces, and by $H$ those which have only three components in the zigzag. We prove that for a surface $S \in A$ the following statements are equivalent: 1. $S$ is isomorphic to a hypersurface; 2. $S$ is isomorphic to a hypersurface, defined by equation $xy=p(z)$ in $\Bbb {C}^3 ,$ where $p$ is a polynomial with simple roots only; 3. $S$ admits a fixed-point free $\Bbb {C}^+$- action; 4. $S\in H.$ Moreover, if $S_1 $ belongs to $H,$ and $S_2$ does not, then $S_1\times \Bbb {C}^k\not\cong S_2\times \Bbb {C}^k$ for any $k\in\Bbb N$.

math.AG↗
arXiv1998

Cylinders over affine surfaces

For an affine variety $S$ we consider the ring $AK(S),$ which is the intersection of the rings of constants of all locally-nilpotent derivations of the ring $\Cal {O}(S).$ We show that $AK(S\times\Bbb {C}^n)=AK(S)$ for a smooth affine surface $S$ with $H^2(S,\Bbb {Z})=\{0\}.$

math.AG↗