operator topologies
Let be a normed vector space and the space of bounded operators in . There are several interesting topologies that can be given to . In what follows, denotes a net in and denotes an element of .
Note: On 4, 5, 6 and 7, must be a Hilbert space.
0.1 1. Norm Topology
This is the topology induced by the usual operator norm.
0.2 2. Strong Operator Topology
This is the topology generated by the family of semi-norms defined by . That means
0.3 3. Weak Operator Topology
This is the topology generated by the family of semi-norms , where and is a linear functional of (written , the dual vector space of ), defined by . That means
In case is an Hilbert space with inner product , we have that
0.4 4. -Strong Operator Topology
In this topology must be a Hilbert space. Let denote the space of compact operators on .
The -strong operator topology is the topology generated by the family of semi-norms , defined by . That means
Equivalently, in norm for every .
This topology is also called the ultra-strong operator topology.
0.5 5. -Weak Operator Topology
In this topology must be a Hilbert space. Let denote the space of trace-class operators on and the trace of an operator .
The -weak operator topology is the topology generated by the family of semi-norms defined by . That means
This topology is also called the ultra-weak operator topology.
0.6 6. Strong-* Operator Topology
In this topology must be a Hilbert space. In the following denotes the adjoint operator of .
The strong-* operator topology is the topology generated by the family of semi-norms defined by . That means
Equivalently, if and only if and , for every .
0.7 7. -Strong-* Operator Topology
In this topology must be a Hilbert space. Let denote the space of compact operators on . In the following denotes the adjoint operator of .
The -strong-* operator topology is the topology generated by the family of semi-norms defined by . That means
Equivalently, if and only if and in norm, for every .
This topology is also called ultra-strong-* operator topology.
0.8 Comparison of Operator Topologies
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The norm topology is the strongest of the topologies defined above.
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The weak operator topology is weaker than the strong operator topology, which is weaker than the norm topology.
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In Hilbert spaces we can summarize the relations of the above topologies in the following diagram. Given two topologies the notation means is weaker than :
Title | operator topologies |
---|---|
Canonical name | OperatorTopologies |
Date of creation | 2013-03-22 17:22:04 |
Last modified on | 2013-03-22 17:22:04 |
Owner | asteroid (17536) |
Last modified by | asteroid (17536) |
Numerical id | 18 |
Author | asteroid (17536) |
Entry type | Definition |
Classification | msc 54E99 |
Classification | msc 47L05 |
Classification | msc 46A32 |
Related topic | OperatorNorm |
Defines | strong operator topology |
Defines | weak operator topology |
Defines | -weak operator topology |
Defines | -strong operator topology |
Defines | strong-* operator topology |
Defines | -strong-* operator topology |
Defines | ultra-strong operator topology |
Defines | ultra-weak operator topology |
Defines | ultra-stro |