Is it Possible to Embed F/R into F without Complementation?

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In summary, the conversation discusses the possibility of embedding F/R into F and the concept of complementation in this process. The use of semidirect products and the necessary and sufficient condition for this embedding to occur are also mentioned. The use of F and R to denote groups is questioned.
  • #1
tgt
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Why doesn't such an embedding exist? When R is a normal subgroup of F.
 
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  • #2
Why would such an embedding exist? Conceptually it doesn't make sense.

By way of example, can you embed Z/2Z into Z?
 
  • #3
morphism said:
Why would such an embedding exist? Conceptually it doesn't make sense.

By way of example, can you embed Z/2Z into Z?

Sure, I see the exampe but can you explain the conceptual part? How is it conceptual to you?
 
  • #4
Well, if you think about it for a bit, what does it mean to be able to embed F/R into F? Intuitively, modding out by a subgroup means you collapse that subgroup to zero. So for F/R to be isomorphic to some subgroup of F, it would be necessary for R to be 'complemented' inside of F by another subgroup (think of complementation here as you would in the setting of vector spaces). I personally don't see any reason why one would believe every normal subgroup of F to have this property. (But I admit to being prejudiced: functional analysis has made me very suspicious of the process of complementation!)

To make this a bit more precise, we can use semidirect products: If F/R embeds into F, then F is essentially [itex]R \rtimes F/R[/itex]. It's easy to see that a necessary and sufficient condition for this to happen is that the canonical exact sequence

[tex]1 \longrightarrow R \longrightarrow F \longrightarrow F/R \longrightarrow 1[/tex]

splits.

By the way, is there any specific reason you're using F and R to denote groups?!
 
  • #5
morphism said:
Well, if you think about it for a bit, what does it mean to be able to embed F/R into F? Intuitively, modding out by a subgroup means you collapse that subgroup to zero. So for F/R to be isomorphic to some subgroup of F, it would be necessary for R to be 'complemented' inside of F by another subgroup (think of complementation here as you would in the setting of vector spaces). I personally don't see any reason why one would believe every normal subgroup of F to have this property. (But I admit to being prejudiced: functional analysis has made me very suspicious of the process of complementation!)

To make this a bit more precise, we can use semidirect products: If F/R embeds into F, then F is essentially [itex]R \rtimes F/R[/itex]. It's easy to see that a necessary and sufficient condition for this to happen is that the canonical exact sequence

[tex]1 \longrightarrow R \longrightarrow F \longrightarrow F/R \longrightarrow 1[/tex]

splits.

By the way, is there any specific reason you're using F and R to denote groups?!

Some good points raised. Although what does split mean?

Those notations naturally fit into the notation of a presentation.
 
Last edited:

1. Why is embedding F/R into F important?

Embedding F/R into F is important because it allows for a more efficient and streamlined approach to conducting scientific research. By embedding F/R, researchers can easily access and analyze data, collaborate with other scientists, and share their findings with the scientific community.

2. What is the process of embedding F/R into F?

The process of embedding F/R into F involves integrating the functions and resources of F and R into one cohesive system. This can be achieved through the use of APIs, plugins, or other integration methods.

3. How does embedding F/R into F benefit scientists?

Embedding F/R into F benefits scientists by providing them with a more comprehensive and efficient tool for conducting research. It allows for easier data management, collaboration, and analysis, ultimately saving time and resources.

4. Are there any challenges to embedding F/R into F?

Yes, there can be challenges to embedding F/R into F. These may include compatibility issues, technical difficulties, and the need for specialized expertise in both F and R systems.

5. Can any research project benefit from embedding F/R into F?

While embedding F/R into F can greatly benefit many research projects, it may not be necessary or suitable for all projects. It is important for researchers to carefully evaluate their needs and resources before deciding to embed F/R into F.

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