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Further refinements of generalized numerical radius inequalities for Hilbert space operators
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Abstract
In this paper, we show some refinements of generalized numerical radius inequalities involving the Young and Heinz inequality. In particular, we present
w
p
p
(
A
1
*
T
1
B
1
,
…
,
A
n
*
T
n
B
n
)
≤
n
1
-
1
r
2
1
r
∥
∑
i
=
1
n
[
B
i
*
f
2
(
|
T
i
|
)
B
i
]
r
p
+
[
A
i
*
g
2
(
|
T
i
*
|
)
A
i
]
r
p
∥
1
r
-
inf
∥
x
∥
=
1
η
(
x
)
,
w_{p}^{p}(A_{1}^{*}T_{1}B_{1},\dots,A_{n}^{*}T_{n}B_{n})\leq\frac{n^{1-\frac{1%
}{r}}}{2^{\frac{1}{r}}}\bigg{\|}\sum_{i=1}^{n}[B_{i}^{*}f^{2}(|T_{i}|)B_{i}]^{%
rp}+[A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i}]^{rp}\bigg{\|}^{\frac{1}{r}}-\inf_{\|x\|%
=1}\eta(x),
where
T
i
,
A
i
,
B
i
∈
????
(
ℋ
)
{T_{i},A_{i},B_{i}\in\mathbb{B}(\mathscr{H})}
(
1
≤
i
≤
n
)
{(1\leq i\leq n)}
, f and g are nonnegative continuous functions on
[
0
,
∞
)
{[0,\infty)}
satisfying
f
(
t
)
g
(
t
)
=
t
{f(t)g(t)=t}
for all
t
∈
[
0
,
∞
)
{t\in[0,\infty)}
,
p
,
r
≥
1
{p,r\geq 1}
,
N
∈
ℕ
{N\in\mathbb{N}}
, and
η
(
x
)
=
1
2
∑
i
=
1
n
∑
j
=
1
N
(
〈
(
A
i
*
g
2
(
|
T
i
*
|
)
A
i
)
p
x
,
x
〉
2
j
-
1
-
k
j
〈
(
B
i
*
f
2
(
|
T
i
|
)
B
i
)
p
x
,
x
〉
k
j
2
j
\displaystyle\eta(x)=\frac{1}{2}\sum_{i=1}^{n}\sum_{j=1}^{N}\Bigl{(}\sqrt[2^{j%
}]{\big{\langle}(A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i})^{p}x,x\big{\rangle}^{2^{j-1%
}-k_{j}}\big{\langle}(B_{i}^{*}f^{2}(|T_{i}|)B_{i})^{p}x,x\big{\rangle}^{k_{j}}}
-
〈
(
B
i
*
f
2
(
|
T
i
|
)
B
i
)
p
x
,
x
〉
k
j
+
1
〈
(
A
i
*
g
2
(
|
T
i
*
|
)
A
i
)
p
x
,
x
〉
2
j
-
1
-
k
j
-
1
2
j
)
2
.
\displaystyle -\sqrt[2^{j}]{\big{\langle}(B_{i}^{*}f^{2}(|T_{i}|)B_{i}%
)^{p}x,x\big{\rangle}^{k_{j}+1}\big{\langle}(A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i})%
^{p}x,x\big{\rangle}^{2^{j-1}-k_{j}-1}}\,\Big{)}^{2}.
Walter de Gruyter GmbH
Title: Further refinements of generalized numerical radius inequalities for Hilbert space operators
Description:
Abstract
In this paper, we show some refinements of generalized numerical radius inequalities involving the Young and Heinz inequality.
In particular, we present
w
p
p
(
A
1
*
T
1
B
1
,
…
,
A
n
*
T
n
B
n
)
≤
n
1
-
1
r
2
1
r
∥
∑
i
=
1
n
[
B
i
*
f
2
(
|
T
i
|
)
B
i
]
r
p
+
[
A
i
*
g
2
(
|
T
i
*
|
)
A
i
]
r
p
∥
1
r
-
inf
∥
x
∥
=
1
η
(
x
)
,
w_{p}^{p}(A_{1}^{*}T_{1}B_{1},\dots,A_{n}^{*}T_{n}B_{n})\leq\frac{n^{1-\frac{1%
}{r}}}{2^{\frac{1}{r}}}\bigg{\|}\sum_{i=1}^{n}[B_{i}^{*}f^{2}(|T_{i}|)B_{i}]^{%
rp}+[A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i}]^{rp}\bigg{\|}^{\frac{1}{r}}-\inf_{\|x\|%
=1}\eta(x),
where
T
i
,
A
i
,
B
i
∈
????
(
ℋ
)
{T_{i},A_{i},B_{i}\in\mathbb{B}(\mathscr{H})}
(
1
≤
i
≤
n
)
{(1\leq i\leq n)}
, f and g are nonnegative continuous functions on
[
0
,
∞
)
{[0,\infty)}
satisfying
f
(
t
)
g
(
t
)
=
t
{f(t)g(t)=t}
for all
t
∈
[
0
,
∞
)
{t\in[0,\infty)}
,
p
,
r
≥
1
{p,r\geq 1}
,
N
∈
ℕ
{N\in\mathbb{N}}
, and
η
(
x
)
=
1
2
∑
i
=
1
n
∑
j
=
1
N
(
〈
(
A
i
*
g
2
(
|
T
i
*
|
)
A
i
)
p
x
,
x
〉
2
j
-
1
-
k
j
〈
(
B
i
*
f
2
(
|
T
i
|
)
B
i
)
p
x
,
x
〉
k
j
2
j
\displaystyle\eta(x)=\frac{1}{2}\sum_{i=1}^{n}\sum_{j=1}^{N}\Bigl{(}\sqrt[2^{j%
}]{\big{\langle}(A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i})^{p}x,x\big{\rangle}^{2^{j-1%
}-k_{j}}\big{\langle}(B_{i}^{*}f^{2}(|T_{i}|)B_{i})^{p}x,x\big{\rangle}^{k_{j}}}
-
〈
(
B
i
*
f
2
(
|
T
i
|
)
B
i
)
p
x
,
x
〉
k
j
+
1
〈
(
A
i
*
g
2
(
|
T
i
*
|
)
A
i
)
p
x
,
x
〉
2
j
-
1
-
k
j
-
1
2
j
)
2
.
\displaystyle -\sqrt[2^{j}]{\big{\langle}(B_{i}^{*}f^{2}(|T_{i}|)B_{i}%
)^{p}x,x\big{\rangle}^{k_{j}+1}\big{\langle}(A_{i}^{*}g^{2}(|T_{i}^{*}|)A_{i})%
^{p}x,x\big{\rangle}^{2^{j-1}-k_{j}-1}}\,\Big{)}^{2}.
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