科研之友
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摘要
Let H be a complex Hilbert space and let delta be a linear map which is Jordan derivable at a given idempotent P is an element of B(H) in the sense that delta(A(2)) = delta(A)A + A delta(A) holds for all A with A(2) = P. If P has infinite rank and co-rank, then we prove that the restriction of delta to B(ImP) is an inner derivation and the restriction to B(KerP) is a sum of inner derivation and multiplication by a scalar. We give an example that this is not necessarily true when rank and co-rank of P are finite.
