Affiliation:
1. Department of Mathematics , Aligarh Muslim University , Aligarh 202002 , India
Abstract
Abstract
Let
𝔄
{\mathfrak{A}}
be a standard operator algebra on a complex Banach space
𝔛
{\mathfrak{X}}
,
dim
𝔛
>
1
{\dim\mathfrak{X}>1}
, and
p
n
(
T
1
,
T
2
,
…
,
T
n
)
{p_{n}(T_{1},T_{2},\dots,T_{n})}
the
(
n
-
1
)
{(n-1)}
th-commutator of elements
T
1
,
T
2
,
…
,
T
n
∈
𝔄
{T_{1},T_{2},\dots,T_{n}\in\mathfrak{A}}
.
Then every map
ξ
:
𝔄
→
𝔄
{\xi:\mathfrak{A}\rightarrow\mathfrak{A}}
(not necessarily linear) satisfying
ξ
(
p
n
(
T
1
,
T
2
,
…
,
T
n
)
)
=
∑
i
=
1
n
p
n
(
T
1
,
T
2
,
…
,
T
i
-
1
,
ξ
(
T
i
)
,
T
i
+
1
,
…
,
T
n
)
{\xi(p_{n}(T_{1},T_{2},\dots,T_{n}))=\sum_{i=1}^{n}p_{n}(T_{1},T_{2},\dots,T_{%
i-1},\xi(T_{i}),T_{i+1},\dots,T_{n})}
for all
T
1
,
T
2
,
…
,
T
n
∈
𝔄
{T_{1},T_{2},\dots,T_{n}\in\mathfrak{A}}
is of the form
ξ
=
Ω
+
Γ
{\xi=\Omega+\Gamma}
, where
Ω
:
𝔄
→
𝔄
{\Omega:\mathfrak{A}\rightarrow\mathfrak{A}}
is an additive derivation and
Γ
:
𝔄
→
ℂ
I
{\Gamma:\mathfrak{A}\rightarrow\mathbb{C}I}
is a map that vanishes at each
(
n
-
1
)
{(n-1)}
th-commutator
p
n
(
T
1
,
T
2
,
…
,
T
n
)
{p_{n}(T_{1},T_{2},\dots,T_{n})}
for all
T
1
,
T
2
,
…
,
T
n
∈
𝔄
{T_{1},T_{2},\dots,T_{n}\in\mathfrak{A}}
.
In addition, if the map ξ is linear and satisfies the above relation, then there exist an operator
S
∈
𝔄
{S\in\mathfrak{A}}
and a
linear map
Γ
:
𝔄
→
ℂ
I
{\Gamma:\mathfrak{A}\rightarrow\mathbb{C}I}
satisfying
Γ
(
p
n
(
T
1
,
T
2
,
…
,
T
n
)
)
=
0
{\Gamma(p_{n}(T_{1},T_{2},\dots,T_{n}))=0}
for all
T
1
,
T
2
,
…
,
T
n
∈
𝔄
{T_{1},T_{2},\dots,T_{n}\in\mathfrak{A}}
, such that
ξ
(
T
)
=
[
T
,
S
]
+
Γ
(
T
)
{\xi(T)=[T,S]+\Gamma(T)}
for all
T
∈
𝔄
{T\in\mathfrak{A}}
.