Proving F-Isomorphism Between E and K

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Discussion Overview

The discussion revolves around the question of whether two field extensions E and K over a common field F, which are isomorphic, must also be F-isomorphic. Participants explore the implications of this relationship and seek to prove or find a counterexample to the claim.

Discussion Character

  • Debate/contested
  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that if E and K are isomorphic, then they should be F-isomorphic, but they question whether this holds in general.
  • Others clarify that E and K are extensions of F, but the nature of these extensions (finite or transcendental) is not specified.
  • A participant suggests looking for a counterexample where E and K are isomorphic but not F-isomorphic, indicating the complexity of the problem.
  • Another participant mentions a professor's opinion that the result is not true and encourages the search for a counterexample, highlighting the non-trivial nature of the problem.
  • There is a discussion about the need for two fields that are isomorphic but do not preserve F under any automorphism, suggesting a deeper exploration of field properties.
  • Some participants express uncertainty about their ideas and the validity of their approaches, indicating a collaborative but tentative exploration of the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the truth of the claim regarding F-isomorphism. There are competing views, and the discussion remains unresolved as participants seek counterexamples and clarification.

Contextual Notes

Participants acknowledge the complexity of the problem and the potential for missing assumptions or definitions that could affect the outcome of their reasoning.

Palindrom
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O.K.
Here it is:
Prove or find a counter example.
Suppose E/F, and K/F. Then E~K (iso.) => E and K are F-isomorphic.

I can prove it for F=Q or any finite field.
Is it true in general?
 
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Suppose E/F and K/F are what?
 
matt grime said:
Suppose E/F and K/F are what?
I'm sorry- just assume E and K are extensions of F.
 
Finite or transcendental?
 
matt grime said:
Finite or transcendental?
It's not mentioned... I guess either of them.
You got any leads?
 
Help... anyone?

It's to be handed in tomorrow... I really don't know where to start.
 
Try thinking instead of field E(=K) with a subfield (F) that is not preserved by any automorphism of E.
 
So you're going for the counter example?

I tried your idea, but I couldn't find an example.
(I really did :) )

Are you sure it's wrong?
 
btw, it wouldn't be good- because E is still F-isomorphic to itself.

I would need 2 fields that aren't F-iso. (and of course, I'd have to prove they aren't)...
 
  • #10
All I said was, sicne E and K are isomorphic, that we may replace K with E. That is is there a Field, which cotains a subfield (over which it is an extension), such that no isomorphism is an F-isomorphism. I really have just restated the question: any F-isomorphism is still an isomorphism.

I don't know whether the result is true to be honest.
 
  • #11
Well, I went to see my Professor today- he said it wasn't true.
Told me to keep thinking about a counter example, and that it's quite untrivial. He promised to answer me next week though.

I must have not understood what you meant, by the way- didn't you suggest that I would find an extension E of F that has no F automorphisms? Because that's what I thought you said, I apologize if I got you wrong.
 
  • #12
No I said to find two objects that are isomprohic, ie we may as well replace them the same symbol and that contain F as (sub)field over which they are extensions such that no automorphism preserves F. I had a feeling there would be a counter example, and I feel that I ought to be able to come up with one, but I've not spent long enough on it, and, if you don't mind, dont' really intend to try figuring it out.
 
  • #13
I'm not asking you to, if you don't want to.
I feel you might be a bit insulted- if you are, it is absolutely not my intention.
 
  • #14
Oh, no I'm not insulted, and I now think my idea is absolutely crap to boot.
 
  • #15
:smile:
Then you must know how I feel... I'll keep trying though, if I finish up all the other weird stuff I have to do.
Have a nice weekend...
 
  • #16
Oh, I have one stupid idea an hour or its a slow day. SOmetimes I sadly tell other people of the stupid idea before I figure out its stupid. And they pay me to do this...
 
  • #17
You want to hear stupid?

About 3 or 4 friends of mine thought for about 3 days about the next problem: Find a function that isn't L1 but whose derivative is.

Then one of them got a brilliant idea: take f(x)=const.

And you should have seen what they where trying to do before that idea- I heard the words "delta function" quite a few times that week...
 

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