If you look at the configuration space of a robot arm, it is a manifold. Does this manifold exist in the same sense as strings in string theory? Or do the strings in string theory exist in another sense? Does string theory raise new questions about which objects actually exist, and the different levels of physical existence? For example, how do spacetime and particles exist? And if we accept the holographic principle can everything exist on a boundary? But which description is the right one, or are both right and this is a duality that violates our intuition like the wave-particle duality?

For the purposes of this question you may assume string theory to be true, I am interested in philosophical approaches to understanding its ontology given holography and multiple dualities.

  • Dualities are mathematical in nature and not necessarily ontological. Take AdS/CFT for an example, the statement "a physical description of a black hole in 5 dimensional AdS super string theory is dual to a description in a n=4 yang mills theory" is just the statement that there are two ways to describe something. String dualities are useful because sometimes its easier to calculate something in AdS and sometimes its easier in a CFT, but that doesn't say anything necessarily ontological about what the actual thing you're describing is. It has nothing to do with wave and particle duality. – Not_Here May 13 '17 at 21:47
  • The biggest objection to string theory (besides the fact that it might be untestable and therefore unfalsifiable) is that it is just a bunch of mathematical tools. Those dualities are not telling us that there is some ontological dual world that exists, it is just saying that there are two equivalent ways to mathematically describe the same thing. Remember that all examples of AdS/CFT that we have do not describe our own world, we don't live in a five dimensional AdS or the specific N=4 Yang Mills (which has no gravity). It is just an example of a mathematical duality in describing something – Not_Here May 13 '17 at 21:51
  • @Not_Here But if we extend the same logic to classical physics and relativity should we not reject existence of spacetime, etc.? After all, there is the hole argument and alternative formulations (twistors, differential algebras) that eliminate manifold points from the picture. Is this not a universal argument for scientific anti-realism? Under the OP stipulation that the string theory is "true" (and our best theory, presumably), doesn't its polymorphism pose serious obstacles to anyone wishing to be a realist about it? What is real according to string theory? – Conifold May 13 '17 at 22:36
  • Nobody knows whats real according to string theory because string theory isn't fully formed. Go ask a string theorist if spacetime is continuous or discrete in string theory and they'll tell you it is either neither and both at the same time or they'll say we have absolutely no idea. Yes obviously that's an argument for antirealsim. If the point of science is to make accurate predictions and sometimes mathematical tools that give us better predictions don't agree with the actual ontology of the situation, we still use those tools to make predictions. – Not_Here May 13 '17 at 22:44
  • Virtual particles exchanged during a scattering process in a QFT do not physically exist, they're not real particles. But they are a mathematical tool that allows us to more accurately predict the outcome of an event so we use them. Or maybe it's more accurate to say that it allows us to make the computation of that problem more practical to do, either way they posit something that doesn't really exist but we use it anyway because it makes the math easier and allows us to make better predictions. – Not_Here May 13 '17 at 22:45

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