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Given the flexibility of it, I've seen some people claim that this is essentially String Theory, and that's why it's not a suitable model. While the math works

Given the flexibility of it, I've seen some people claim that this is essentially String Theory, and that's why it's not a suitable model. While the math works out, it also has so many tune-ables that you can make any kind of universe you want, and take any observations and make any number of universes that fit those observations. And since these tune-ables aren't inherit properties of any kind, just numbers (or other kinds of values) you can plug in, there's very little predictive power in the theory. You can just always re-tune the whole thing to any observation, and make a nearly infinite number of predictions from it still. There's no way to try to select for anything that looks like a fundamental property of the universe.

philipov 9y ago
That's because string theory is not a model, it is a framework for model-building; just like the Standard Model is only one possible quantum field theory. String theory is fully compatible with quantum field theory, so the current state of theoretical research is seeing them come to live side by side as two tools within a single discipline. The problem really is that string theory provides a language for discussing phenomena we can't probe directly (due to the extreme energies involved), and so theoreticians are stuck conducting thought experiments until new experimental options are developed/discovered for testing particular models making use of string theory. Until then, there's no real path forward for applying that framework to expand or amend the Standard Model, because of how successful quantum field theories have been at explaining the phenomena we have access to currently. Because we will never be able to build a galactic-scale particle accelerator required for doing scattering experiments at planckian energies, astronomical observations offer one of the best hopes for getting access to contradictory data. The study of holographic duality offers another possibility, if we can devise lower energy systems within our experimental grasp that are dual to high energy systems that aren't.

philipov 9y ago

That's because string theory is not a model, it is a framework for model-building; just like the Standard Model is only one possible quantum field theory. String theory is fully compatible with quantum field theory, so the current state of theoretical research is seeing them come to live side by side as two tools within a single discipline. The problem really is that string theory provides a language for discussing phenomena we can't probe directly (due to the extreme energies involved), and so theoreticians are stuck conducting thought experiments until new experimental options are developed/discovered for testing particular models making use of string theory. Until then, there's no real path forward for applying that framework to expand or amend the Standard Model, because of how successful quantum field theories have been at explaining the phenomena we have access to currently. Because we will never be able to build a galactic-scale particle accelerator required for doing scattering experiments at planckian energies, astronomical observations offer one of the best hopes for getting access to contradictory data. The study of holographic duality offers another possibility, if we can devise lower energy systems within our experimental grasp that are dual to high energy systems that aren't.