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Necessity of surjectivity in commutator-ideal splitting for Jordan homomorphisms

Ascertain whether the surjectivity assumption in the following statement is necessary: if A is a unital associative algebra with commutator ideal K(A)=A, then for every Jordan homomorphism φ: A → B there exists a central idempotent e in B such that x ↦ eφ(x) is a homomorphism and x ↦ (1−e)φ(x) is an antihomomorphism.

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Background

The paper proves that for unital algebras A satisfying K(A)=A, every Jordan epimorphism φ: A → B splits via a central idempotent into a homomorphism and an antihomomorphism. This provides a strong structural insight when the image of φ is an associative algebra.

It remains unclear whether the epimorphism (surjectivity onto its image) requirement is essential. Removing this assumption would significantly strengthen the commutator-ideal approach to Jordan homomorphisms and broaden applicability beyond epimorphic cases.

References

Since B is an arbitrary algebra, the condition that φ is surjective only means that its image is an associative algebra. We do not know whether this assumption is necessary.

Jordan homomorphisms: A survey (2510.16876 - Brešar et al., 19 Oct 2025) in Section 8 (Jordan homomorphisms on commutator ideals), after Theorem 8 (Theorem mt1)