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What are the five string theories?

  1. Oct 29, 2003 #1
    i can not seem to find any good or relevent information on the five different string theories and how they differ from one another. i know of, and to the best of my ability try to understand 'basic' M-theory but am very strapped for info on the other theories and thier specifics. if some one could endulge me i'd be very greatful.[?]
  2. jcsd
  3. Oct 29, 2003 #2
    Well, actually, M-Theory is the combination/unification of the five string theories (along with the introduction of a sixth string theory), through the use of Duality. A good resource on this is Brian Greene's The Elegant Universe.
  4. Oct 29, 2003 #3
    OK, what ARE the six theories and thier properties? I'd like to recieve as much info as possible so i can better my understanding of M-theory and the unification model.
  5. Oct 29, 2003 #4
  6. Oct 29, 2003 #5
    To speak properly, they are not string theories, but superstring theories. Type I is the only that admits both closed and open strings, while the other 4 (Type IIA, type IIB, heterotic SO(32) and heterotic E8XE8) admit only closed strings. Each of the 5 superstring theories lives in a different background space.Theories related through the T-duality are the two heterotic between them, and the two type II between them. Theories related through the S-duality are Type I with heterotic SO(32), and Type IIB with itself. If you compactify M-theory in a circle (with some additional conditions) you get superstring theory type IIA, and if you compactify M-theory in a line (with some additional conditions)you get heterotic E8XE8
    Heterotic E8XE8 is special in the sense that is the only that postulates the existence of a twin universe of ours called shadow universe or hidden sector. The only interaction permitted between the two universes is the gravitational interaction
    If this is not enough ask for more :wink:
  7. Oct 29, 2003 #6
    good enough:wink:
  8. Oct 30, 2003 #7
    "and?", as I mentioned before, The Elegant Universe is a very good resource for learning about superstring theories. I highly recommend it.
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