English

Jordan homomorphisms and T-ideals

Rings and Algebras 2025-08-12 v1

Abstract

Let AA and BB be associative algebras over a field FF with {\rm char}(F)2(F)\ne 2. Our first main result states that if AA is unital and equal to its commutator ideal, then every Jordan epimorphism φ:AB\varphi:A\to B is the sum of a homomorphism and an antihomomorphism. Our second main result concerns (not necessarily surjective) Jordan homomorphisms from H(A,)H(A,*) to BB, where * is an involution on AA and H(A,)={aAa=a}H(A,*)=\{a\in A\,|\, a^*=a\}. We show that there exists a T{\rm T}-ideal GG having the following two properties: (1) the Jordan homomorphism φ:H(G(A),)B\varphi:H(G(A),*)\to B can be extended to an (associative) homomorphism, subject to the condition that the subalgebra generated by φ(H(A,))\varphi(H(A,*)) has trivial annihilator, and (2) every element of the T{\rm T}-ideal of identities of the algebra of 2×22\times 2 matrices is nilpotent modulo GG. A similar statement is true for Jordan homomorphisms from AA to BB. A counter-example shows that the assumption on trivial annihilator cannot be removed.

Keywords

Cite

@article{arxiv.2508.07191,
  title  = {Jordan homomorphisms and T-ideals},
  author = {Matej Brešar and Efim Zelmanov},
  journal= {arXiv preprint arXiv:2508.07191},
  year   = {2025}
}
R2 v1 2026-07-01T04:42:51.676Z