چکیده
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In this Thesis, let A be a -algebra over the complex field C. For A;B 2 A; we define, the new products of A and B by A B = AB + BA; A ◦ B = AB BA: Then we establish the structure of the nonlinear maps preserving the mixed product (A B ◦ C) on von Neumann algebras. Also, we assume that be a unital -algebra with the unit I and A contains a nontrivial projection P which satisfies XAP = 0 implies X = 0 and XA(I P) = 0 implies X = 0 Then a map : A ! A satisfies (A B ◦ C) = (A) B ◦ C + A (B) ◦ C + A B ◦ (C) for all A;B;C 2 A if and only if is an additive -derivation. Then we prove that if A be a factor von Neumann algebra with dimA 2; then a map : A ! A satisfies (A B ◦ C) = (A) B ◦ C + A (B) ◦ C + A B ◦ (C) for all A;B;C 2 A if and only if is an additive -derivation.
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