<p>This paper investigates certain properties of <i>n</i>-Jordan homomorphisms between algebras (rings). We first show that every <i>n</i>-Jordan homomorphism <i>T</i> from a ring <i>A</i> into a commutative reduced algebra <i>B</i> is an <i>n</i>-homomorphism. For the case where <i>A</i> is a Banach algebra and <i>B</i> is a semisimple commutative Banach algebra, we prove that any linear <i>n</i>-Jordan homomorphism <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1947_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="83" /> </InlineMediaObject> <EquationSource Format="TEX">\(T : A \rightarrow B\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mo>:</mo> <mi>A</mi> <mo stretchy="false">→</mo> <mi>B</mi> </mrow> </math></EquationSource> </InlineEquation> is automatically continuous, even if the algebras <i>A</i> and <i>B</i> are not unital. Furthermore, we show that every surjective, <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1947_Article_IEq2.gif" Format="GIF" Height="9" Rendition="HTML" Resolution="72" Type="Linedraw" Width="12" /> </InlineMediaObject> <EquationSource Format="TEX">\(*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow /> <mo>∗</mo> </mrow> </math></EquationSource> </InlineEquation>-preserving linear <i>n</i>-Jordan homomorphism from a unital C*-algebra into a C*-algebra is norm-decreasing and hence automatically continuous. We then provide a complete characterization of bijective <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1947_Article_IEq2.gif" Format="GIF" Height="9" Rendition="HTML" Resolution="72" Type="Linedraw" Width="12" /> </InlineMediaObject> <EquationSource Format="TEX">\(*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow /> <mo>∗</mo> </mrow> </math></EquationSource> </InlineEquation>-preserving linear <i>n</i>-Jordan homomorphisms between unital C*-algebras. Finally, we strengthen this result by proving that every continuous bijective linear <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40840_2025_1947_Article_IEq2.gif" Format="GIF" Height="9" Rendition="HTML" Resolution="72" Type="Linedraw" Width="12" /> </InlineMediaObject> <EquationSource Format="TEX">\(*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow /> <mo>∗</mo> </mrow> </math></EquationSource> </InlineEquation>-preserving <i>n</i>-Jordan homomorphism between nonunital C*-algebras is an isometry. To achieve this, we show that the second adjoint of a continuous linear <i>n</i>-Jordan homomorphism between Arens regular Banach algebras is also an <i>n</i>-Jordan homomorphism.</p>

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On n-Jordan Homomorphisms between Banach Algebras

  • Taher Ghasemi Honary,
  • Hakimeh Mahyar,
  • Mehrad Mostofi Sadri

摘要

This paper investigates certain properties of n-Jordan homomorphisms between algebras (rings). We first show that every n-Jordan homomorphism T from a ring A into a commutative reduced algebra B is an n-homomorphism. For the case where A is a Banach algebra and B is a semisimple commutative Banach algebra, we prove that any linear n-Jordan homomorphism \(T : A \rightarrow B\) T : A B is automatically continuous, even if the algebras A and B are not unital. Furthermore, we show that every surjective, \(*\) -preserving linear n-Jordan homomorphism from a unital C*-algebra into a C*-algebra is norm-decreasing and hence automatically continuous. We then provide a complete characterization of bijective \(*\) -preserving linear n-Jordan homomorphisms between unital C*-algebras. Finally, we strengthen this result by proving that every continuous bijective linear \(*\) -preserving n-Jordan homomorphism between nonunital C*-algebras is an isometry. To achieve this, we show that the second adjoint of a continuous linear n-Jordan homomorphism between Arens regular Banach algebras is also an n-Jordan homomorphism.