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Journal of Applied Mathematics and Physics, 2019, 7, 1251-1262
http://www.scirp.org/journal/jamp
ISSN Online: 2327-4379
ISSN Print: 2327-4352
DOI:
10.4236/jamp.2019.76085 Jun. 19, 2019 1251
Journal of Applied Mathematics and Physics
A Note on Numerical Radius Operator Spaces
Yuanyi Wang
1
, Yafei Zhao
2
1
College of Science and Technology, Ningbo University, Ningbo, China
2
Department of Mathematics, Zhejiang International Studies University, Hangzhou, China
Abstract
In this paper, we first study some
-completely
bounded maps between
various numerical radius operator spaces. We also study the dual space of a
numerical radius operator space and show that it has a dual realization. At
last, we define two special numerical radius operator spaces
MinE
and
MaxE
which can be seen as a quantization of norm space
E
.
Keywords
Numerical Radius Operator Space, Dual Space, Quantization
1. Introduction and Preliminaries
The theory of operator space is a recently arising area in modern analysis, which
is a natural non-commutative quantization of Banach space theory. An operator
space is a norm closed subspace of
( )
. The study of operator space begins
with Arverson’s [1] discovery of an analogue of the Hahn-Banach theorem.
Since the discovery of an abstract characterization of operator space by Ruan [2],
there have been many more applications of operator space to other branches in
functional analysis. Effros and Ruan studied the mapping spaces
( )
,CB V W
in
[3] and the minimal and maximal operator spaces in [4]. The fundamental and
systematic developments in the theory of tensor product of operator spaces can
be found in [5] [6]. The tensor products provide a fruitful approach to mapping
spaces and local property. For example, Effros, Ozawa and Ruan [7] showed that
an operator space
V
is nuclear if and only if
V
is locally reflexive and
**
V
is in-
jective. Dong and Ruan [8] showed that an operator space
V
is exact if and only
if
V
is locally reflexive and
**
V
is weak* exact. In [9], Han showed that an op-
erator space
V
satisfies condition
C
if and only if it satisfies conditions
C
′
and
C
′′
. Based on the work of Han, Wang [10] gave a characterization of condition
C
∧
′
on the operator spaces. Amini, Medghalchi and Nikpey [11] proved that an
How to cite this paper:
Wang,
Y.Y. and
Zhao
, Y.F. (2019)
A Note on Numerical
Radius Operator Spaces
.
Journal of Applied
Mathematics and Physics
,
7
, 1251-1262.
https://doi.org/10.4236/jamp.2019.76085
Received:
May 14, 2019
Accepted:
June 16, 2019
Published:
June 19, 2019
Copyright © 201
9 by author(s) and
Scientific
Research Publishing Inc.
This work is licensed under
the Creative
Commons Attribution International
License (CC BY
4.0).
http://creativecommons.org/licenses/by/4.0/
Open Access
Y. Y. Wang, Y. F. Zhao
DOI:
10.4236/jamp.2019.76085 1252
Journal of Applied Mathematics and Physics
injective operator space is global exactness if and only if it is reflexive. The read-
ers may refer to [12] [13] for the basics on operator spaces.
Recently, some new algebraic structures derived from operator spaces also
have been intensively studied. An operator system is a matrix ordered operator
space which plays a profound role in mathematical physics. Kavruk, Paulsen,
Todorov and Tomforde gave a systematic study of tensor products and local
property of operator systems in [14] [15]. In [16], Luthra and Kumar showed
that an operator system is exact if and only if it can be embedded into a Cuntz
algebra. The numerical radius operator space is also an important algebraic
structure which is introduced by Itoh and Nagisa [17] [18]. The conditions to be
a numerical radius space are weaker than the Ruan’s axiom for an operator space.
It is shown that there is a
-complete isometry from a numerical radius oper-
ator space into a Hilbert space with numerical radius norm. They also studied
many relations between the operator spaces and the numerical radius operator
spaces. The category of operator space can be regarded as a subcategory of nu-
merical radius operator space.
We now recall some concepts needed in our paper. An (abstract) operator
space is a complex linear space
V
together with a sequence of norms
( )
n
⋅
on
the
nn×
matrix space
( )
n
MV
for each
n
∈
, which satisfies the following
Ruan’s axioms OI, OII:
( ) ( )
{ }
0
OI : max , ;
0
mn m n
v
vw
w
+
=
( ) ( )
OII :
nm
vv
αβ α β
≤
for all
( ) ( )
,
mn
vMVwMV∈∈
and
( ) ( )
,,
,
nm mn
MM
αβ
∈∈
. If
V
is an (ab-
stract) operator space, then there is a complete isometry
Ψ
from
V
to
( )
,
that is,
( )
( )
,,ij n ij
n
vv
Ψ=
for all
( )
,
,
ij n
v MVn
∈∈
.
An abstract numerical radius operator space is a complex linear space
V
to-
gether with a sequence of norms
( )
n
⋅
on the
nn×
matrix space
( )
n
MV
for each
n∈
, which satisfies the following axioms WI, WII:
( ) (
)
{ }
0
WI : max , ;
0
mn m n
v
vw
w
+
=
( )
( )
2
WII :
nm
vv
αα α
≤
for all
( ) ( )
,
mn
vMVwMW∈∈
and
( )
,
nm
M
α
∈
. Let
( )
ω
⋅
be the numerical
radius norm on
( )
. If
V
is an abstract numerical radius operator space, then
there is a
-complete isometry
Φ
from
( )
,
n
V
to
( )
( )
,
n
ω
, that is,
( )
( )
( )
,,n ij n ij
vv
ω
Φ=
for all
( )
,
,
ij n
v MVn
∈∈
. Given a numerical ra-
dius operator
( )
,
n
V
, we can define an operator space
( )
,
n
V
by
( )
2
0
1
:
00
2
nn
v
OW v
=
for all
( )
n
vMV∈
.
Y. Y. Wang, Y. F. Zhao
DOI:
10.4236/jamp.2019.76085 1253
Journal of Applied Mathematics and Physics
Given abstract numerical radius operator spaces (or operator spaces)
,VW
and a linear map
ϕ
from
V
to
W
,
n
ϕ
from
( )
n
MV
to
( )
n
MW
is defined
to be
( )
,n ij
v
ϕ
for each
( )
,
,
ij n
v MVn
∈∈
. We use a simple notation for
the norm of
( )
,ij n
v v MV
= ∈
to be
( )
v
(resp.
( )
v
) instead of
( )
n
v
(resp.
( )
n
v
), and for the norm of
( )
*
n
f MV∈
to be
(
) (
) ( ) ( )
{ }
*
,
sup : , 1
ij n
f fv v v M V v
==∈≤
.
We denote the norm
n
ϕ
by
( )
( )
( )
( ) ( )
{ }
,
sup : , 1
n n ij n
v v v MV v
ϕϕ
= =∈≤
(resp.
(
)
( )
( )
( )
( )
{ }
,
sup : , 1
n n ij n
v x v MV v
ϕϕ
= =∈≤
).
The
-completely bounded norm (resp. completely bounded norm) of
ϕ
is de-
fined to be
( )
( )
{ }
sup :
n
cb
n
ϕϕ
= ∈
, (resp.
( )
( )
{ }
sup :
n
cb
n
ϕϕ
= ∈
).
We say
ϕ
is
-completely bounded (resp. completely bounded) if
( )
cb
ϕ
<∞
(resp.
( )
cb
ϕ
<∞
), and
ϕ
is
-completely contractive (resp.
completely contractive) if
( )
1
cb
ϕ
≤
(resp.
(
)
1
cb
ϕ
≤
). We call
ϕ
is a
-complete isometry (resp. complete isometry) if
( )
( )
( )
n
vv
ϕ
=
(resp.
( )
( )
( )
n
vv
ϕ
=
) for each
( )
,
n
xMVn∈∈
.
In Section 2, we study the bounded maps on finite dimension numerical ra-
dius operators and commutation C*-algebras. We prove these maps are all
-completely bounded. In Section 3, we study the dual space of a numerical ra-
dius operator space and prove its dual space has a dual realization on a Hil-
bert space
. In Section 4, we define the numerical radius operator spaces
MinE
and
MaxE
for a normed space
E
, and prove that
( )
*
*
MaxE MinE=
and
( )
*
*
MaxE MinE=
.
In order to improve the readability of the paper, we give an index of notation:
Index of Notation
( )
Hilbert space
( )
,mn
MV
m
by
n
matrix space over
V
( )
0
C Ω
Space of continuous complex functions vanishing at
∞
on
Ω
α
Matrix norm of
α
,vw
Scalar pairing of matrices
,vw
Matrix pairing of matrices
( )
,
n
V
Operator space
( )
,
n
V
Numerical radius operator space
( )
ω
⋅
Numerical radius norm on
(
)
( )
,BVW
Space of bounded mappings
( )
,B VW
σ
Space of w*-bounded mappings
( )
,CB V W
Space of completely bounded mappings
( )
,CB V W
Space of
-completely bounded mappings
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