Searcharxiv⌕ Search

arXiv subjects

James J. Zhang

Publications and source records attributed to James J. Zhang.

At least 19 recordsLinked to original sources
arXiv2026

Weighted Poisson polynomial rings in dimension three

We discuss Poisson structures on a weighted polynomial algebra $A:=\Bbbk[x, y, z]$ defined by a homogeneous element $Ω\in A$, called a potential. We start with classifying potentials $Ω$ of degree deg$(x)+$deg$(y)+$deg$(z)$ with any positive weight (deg$(x)$, deg$(y)$, deg$(z)$) and list all with isolated singularity. Based on the classification, we study the rigidity of $A$ in terms of graded twistings and classify Poisson fraction fields of $A/(Ω)$ for irreducible potentials. Using Poisson valuations, we characterize the Poisson automorphism group of $A$ when $Ω$ has an isolated singularity extending a nice result of Makar-Limanov-Turusbekova-Umirbaev. Finally, Poisson cohomology groups are computed for new classes of Poisson polynomial algebras.

math.RA↗
arXiv2026

Poisson valuations

We study Poisson valuations and provide their applications in solving problems related to rigidity, automorphisms, Dixmier property, isomorphisms, and embeddings of Poisson algebras and fields.

math.RA↗
arXiv2026

Poisson fields of two variables

We study invariants and structures of Poisson fields of rational functions in two variables. For four particular families, we classify the members, establish criteria for isomorphisms and, with the exception of the Weyl Poisson field, describe the automorphism groups. Embeddings are also investigated, along with an analog of the Dixmier Conjecture: For which Poisson fields is every Poisson endomorphism an automorphism? The answer is negative for the first family, but positive answers are obtained for several subclasses of the other families. Finally, we exhibit a Poisson field which is not isomorphic to any Poisson field $\Bbbk(x,y)$ for which $\{x,y\}$ is a polynomial in $\Bbbk[x,y]$.

math.RA↗
arXiv2026

Symmetric operads of GK-dimension one

We prove that there is no finitely generated symmetric operad of Gelfand-Kirillov dimension strictly between 1 and 2 that answers an open question posted in 2020. We also classify finitely generated prime symmetric operads of Gelfand-Kirillov dimension 1.

math.RA↗
arXiv2026

Relative Dixmier property for Poisson algebras

Dixmier property concerns the bijectivity of endomorphisms for algebras. We introduce a relative Dixmier property, which is a generalization of the Dixmier property. This new concept has applications in proving that several classes of Poisson algebras possess the Dixmier property, as well as in other topics such as the cancellation problem and the non-existence of Hopf coactions.

math.AG↗
arXiv2025

Relative Cancellation

We introduce and study a relative cancellation property for associative algebras. We also prove a characterization result for polynomial rings which partially answers a question of Kraft.

math.RT↗
arXiv2025

Operads with trivial $\mathbb{A}$-actions

We study operads with trivial $\mathbb{A}$-actions and prove an equivalence between the category of $\mathbb{A}$-trivial operads and that of pseudo-graded-Perm associative algebras. As a consequence, we show that finitely generated $\mathbb{A}$-trivial operads are right noetherian of integral Gelfand-Kirillov dimension and that every element in a prime $\mathbb{A}$-trivial operad is central.

math.RA↗
arXiv2025

Homological regularities and concavities

This paper concerns homological notions of regularity for noncommutative algebras. Properties of an algebra $A$ are reflected in the regularities of certain (complexes of) $A$-modules. We study the classical Tor-regularity and Castelnuovo-Mumford regularity, which were generalized from the commutative setting to the noncommutative setting by Jørgensen and Dong-Wu. We also introduce two new numerical homological invariants: concavity and Artin-Schelter regularity. Artin-Schelter regular algebras occupy a central position in noncommutative algebra and noncommutative algebraic geometry, and we use these invariants to establish criteria which can be used to determine whether a noetherian connected graded algebra is Artin-Schelter regular.

math.RA↗
arXiv2025

Log-ozone groups and centers of polynomial Poisson algebras

In previous work, the authors introduced the ozone group of an associative algebra as the subgroup of automorphisms which fix the center pointwise. The authors studied PI skew polynomial algebras, using the ozone group to understand their centers and to characterize them among graded algebras. In this work, we introduce and study the log-ozone group of a Poisson algebra over a field of positive characteristic. The log-ozone group is then used to characterize polynomial Poisson algebras with skew symmetric structure. We prove that unimodular Poisson algebras with skew symmetric structure have Gorenstein centers. A related result is proved for graded polynomial Poisson algebras of dimension three.

math.RA↗
arXiv2025

Homological Integrals for Weak Hopf Algebras

We introduce the notion of a homological integral for an infinite-dimensional weak Hopf algebra and use the homological integral to prove several structure theorems. For example, we prove that the Artin--Schelter property and the Van den Bergh condition are equivalent for a noetherian weak Hopf algebra, and that the antipode is automatically invertible in this case. We also prove a decomposition theorem that states that any weak Hopf algebra finite over an affine center is a direct sum of Artin--Schelter Gorenstein, Cohen--Macaulay, GK dimension homogeneous weak Hopf algebras.

math.QA↗
arXiv2024

Ozone groups of Artin--Schelter regular algebras satisfying a polynomial identity

We study the ozone group of noetherian Artin--Schelter regular algebras satisfying a polynomial identity (or PI for short). The ozone group was shown in previous work by the authors to be an important invariant in the study of PI skew polynomial rings and their centers. In this paper, we show that skew polynomial rings are in fact characterized as those algebras with maximal rank ozone groups. We also classify those with trivial ozone groups, which must necessarily be Calabi--Yau. This class includes most three-dimensional PI Sklyanin algebras. Further examples and applications are given, including applications to the Zariski Cancellation Problem.

math.RA↗
arXiv2023

Ozone groups and centers of skew polynomial rings

We introduce the ozone group of a noncommutative algebra $A$, defined as the group of automorphisms of $A$ which fix every element of its center. In order to initiate the study of ozone groups, we study PI skew polynomial rings, which have long proved to be a fertile testing ground in noncommutative algebra. Using the ozone group and other invariants defined herein, we give explicit conditions for the center of a PI skew polynomial to be Gorenstein (resp. regular) in low dimension.

math.RA↗
arXiv2023

Weighted homological regularities

Let $A$ be a noetherian connected graded algebra. We introduce and study homological invariants that are weighted sums of the homological and internal degrees of cochain complexes of graded $A$-modules, providing weighted versions of Castelnuovo--Mumford regularity, Tor-regularity, Artin--Schelter regularity, and concavity. In some cases an invariant (such as Tor-regularity) that is infinite can be replaced with a weighted invariant that is finite, and several homological invariants of complexes can be expressed as weighted homological regularities. We prove a few weighted homological identities some of which unify different classical homological identities and produce interesting new ones.

math.RA↗
arXiv2023

Growth of nonsymmetric operads

The paper concerns the Gelfand-Kirillov dimension and the generating series of nonsymmetric operads. An analogue of Bergman's gap theorem is proved, namely, no finitely generated locally finite nonsymmetric operad has Gelfand-Kirillov dimension strictly between $1$ and $2$. For every $r\in \{0\}\cup \{1\}\cup [2,\infty)$ or $r=\infty$, we construct a single-element generated nonsymmetric operad with Gelfand-Kirillov dimension $r$. We also provide counterexamples to two expectations of Khoroshkin and Piontkovski about the generating series of operads.

math.RA↗
arXiv2022

Twists of graded Poisson algebras and related properties

We introduce a Poisson version of the graded twist of a graded associative algebra and prove that every graded Poisson structure on a connected graded polynomial ring $A:=\Bbbk[x_1,\ldots,x_n]$ is a graded twist of a unimodular Poisson structure on $A$, namely, if $π$ is a graded Poisson structure on $A$, then $π$ has a decomposition $$π=π_{unim} +\frac{1}{\sum_{i=1}^n {\rm deg} x_i} E\wedge {\mathbf m}$$ where $E$ is the Euler derivation, $π_{unim}$ is the unimodular graded Poisson structure on $A$ corresponding to $π$, and ${\mathbf m}$ is the modular derivation of $(A,π)$. This result is a generalization of the same result in the quadratic setting. The rigidity of graded twisting, $PH^1$-minimality, and $H$-ozoneness are studied. As an application, we compute the Poisson cohomologies of the quadratic Poisson structures on the polynomial ring of three variables when the potential is irreducible, but not necessarily having isolated singularities.

math.RA↗
arXiv2022

Reflexive hull discriminants and applications

We introduce the reflexive hull discriminant as a tool to study noncommutative algebras that are finitely generated, but not necessarily free, over their centers. As an example, we compute the reflexive hull discriminants for quantum generalized Weyl algebras and use them to determine automorphism groups and other properties, recovering results of Su{á}rez-Alvarez, Vivas, and others.

math.RA↗