What exactly is the string theory landscape?

  • #1

Main Question or Discussion Point

Do the the different calabi-yau space solutions of strings theory exist is isolated space-times or are they a part of a continuous whole with space folding and unfolding as you move though space?
 

Answers and Replies

  • #2
The phrase "string landscape" does not refer to physical space, which is what you seem to be implying, but instead refers to a mathematical parameter space. A very simple example of a parameter space would be if you drew a graph for the bob of a pendulum where the x axis was position, and the y axis was momentum. It would be an ellipse which shows what are the allowed combinations of those two variables with physically realizable. The parameter space for string theory is vastly more complicated but it shows what combinations of the many parameters are possible, and we are trying to find a specific point that matches the real Universe.
 
  • #3
The phrase "string landscape" does not refer to physical space, which is what you seem to be implying, but instead refers to a mathematical parameter space. A very simple example of a parameter space would be if you drew a graph for the bob of a pendulum where the x axis was position, and the y axis was momentum. It would be an ellipse which shows what are the allowed combinations of those two variables with physically realizable. The parameter space for string theory is vastly more complicated but it shows what combinations of the many parameters are possible, and we are trying to find a specific point that matches the real Universe.
So then for any combination of parameters there is a complete specific universe that interacts only with itself and not with a domain of even a marginal variation of parameters. That is, these parameters including the precise folding of a single Calabi-Yau extend unaltered through all of space and time.
 
  • #4
In the traditional Big Bang model, it was assumed that there is only one universe, so only one of these points in the string landscape, which you could think of as allowed universes, would be physically realized. The others would be just allowed values of the parameters. In a parameter space, the points represent allowed values even if they are not physically realized. In more modern theories, such as eternal inflation, there could be an infinite number of universes, so each of these points in the landscape would be physically realized somewhere. They would not be casually connected. The details of the topology that the extra dimensions are compactified on would vary throughout.
 

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