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F theory & M theory

  1. Apr 22, 2003 #1

    MathematicalPhysicist

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    what is the relation between the two theories (if there is a connection between them)?

    thaks in advance.
     
  2. jcsd
  3. Apr 22, 2003 #2
    I haven't even heared of the F-Theory. Do you know anything about it?
     
  4. Apr 22, 2003 #3
    I haven't heard of F-theory either. I know some of M-theory, but perhaps someone should fill us in on what F-theory is.
     
  5. Apr 22, 2003 #4

    Eh

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    F is for "father". It seems to be a 12D string theory that has 2 time dimensions. I'll see if I have any links.
     
  6. Apr 22, 2003 #5
    2 time dimensions?!! That just isn't logical. If everything takes place at a certain point in time, then every spacial point corresponds to a point in time. Does this reasoning allow for another time dimension?
     
  7. Apr 22, 2003 #6
    That Net Advance of Physics from the "Physics Napster" topic links to this: abstract. Have fun wading through that.
     
  8. Apr 23, 2003 #7
    Does anyone have any information on why a theory would even want to incorporate two dimensions of time?
     
  9. Apr 23, 2003 #8
    So, 2 time demensions would mean two directions of entropy! how cool is that?? Any way, Mentat, I was wondering the same thing.
     
  10. Apr 23, 2003 #9
    An idea:
    Could two time demensions allow for the future and the past to exist at the same time? Then, time travel to the past could make sense without breaking the first law of thermodynamics. If someone went to the past, the energy/mass of the universe will remain the same, because the person who went to the past would exist in the future. Since both the future and the past exist, energy/mass is not being lost.
     
  11. Apr 24, 2003 #10
    It couldn't allow for our future and our past to exist at the same time.

    There is some appeal that I can gather from the idea of there being two time dimensions: If there are two time dimensions, then "Pretzeled Time" is possible.
     
  12. Apr 24, 2003 #11
    You mean, "how impossible is that?", don't you? Entropy can't go in more than one direction, it isn't logical (or at least doesn't seem to be).
     
  13. Apr 24, 2003 #12
    Okay, back to the drawing board....
     
  14. Apr 25, 2003 #13
    why?
     
  15. Apr 25, 2003 #14

    dav2008

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    Ok..well..entropy is a NET effect...like on our planet...tons of stuff decreases entropy....but the NET effect on the whole universe is that it goes up...
     
  16. Apr 25, 2003 #15
    can you be more detailed?
     
  17. Apr 25, 2003 #16

    dav2008

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    Hm..I dont know the details but Im just providing a general idea....but ok i just realized with 2 time dimensions i have no clue what would be going on...because time as we know it is in one dimension and we cant even imagine what would happen if there were 2 "times"..
     
  18. Apr 25, 2003 #17
    do you agree that the future might already exist? i think it makes sense, as it solves the paradox involved with time travel to the past.
     
  19. Apr 28, 2003 #18
    Because entropy is one effect. It cannot both be increasing and decreasing at the same time, can it? This would be self-contradictory/paradoxical.
     
  20. Apr 28, 2003 #19
    Think of the terms you're using, Majin. You are using the term "future", which is any point in time that has not already come into existence. This means that the future cannot "already exist", by definition.
     
  21. Apr 28, 2003 #20
    We don't know that the future doesn't exist anymore than we know the past has ceased to exist. We only know what our perceptions tells us and, unfortunately, we only perceive a single slice of time.

    Or as Richard Feynman said:

    It may prove useful in physics to consider events in all of time at once and to imagine that we at each instant are only aware of those that lie behind us.

    Who knows?
     
  22. Apr 28, 2003 #21
    Yes, I have considered that. But in order to actually make time travel feasible, the past/future should already exist. Mentat, consider a closed time loop for example. If I go to the past(from the future), then my going to the past, would have already happened in the future. So, it creates a kind of closed time loop. So the future, could already exist, and the past as well.
     
  23. Apr 28, 2003 #22
    Mentat, the increasing of entropy in two directions could be constant. It does not have to be increasing and decreasing.
     
  24. Apr 29, 2003 #23
    What has the first law of thermodynamics got to do with anything. To recap the first law of thermodynamics is;

    The internal energy of a sytem tends to increase if energy is added via heat and tends to decrease if energy is lost via work done to the system.
     
  25. Apr 29, 2003 #24
    The use of the words "future" and "past" do not, by definition, allow them to "all exist at the same time". Sure, it would be useful to consider them as such. But the words used do not allow for it.
     
  26. Apr 29, 2003 #25
    This is where the problem lies. If you go to the past, then the "past" has to currently exist, making it the "present". Thus, you wouldn't be traveling to the "past". In fact, since it takes a certain amount of time to get to the point that you might consider "the past" you are actually traveling to the future.
     
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