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Target Space ≠ Space

Huggett, Nick (2015) Target Space ≠ Space. [Preprint]

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This paper investigates the significance of T-duality in string theory: the indistinguisha- bility with respect to all observables, of models attributing radically different radii to space – larger than the observable universe, or far smaller than the Planck length, say. Two interpretational branch points are identified and discussed. First, whether duals are physically equivalent or not: by considering a duality of the familiar simple harmonic oscillator, I argue that they are. Unlike the oscillator, there are no measurements ‘outside’ string theory that could distinguish the duals. Second, whether duals agree or disagree on the radius of ‘target space’, the space in which strings evolve according to string theory. I argue for the latter position, because the alternative leaves it unknown what the radius is. Since duals are physically equivalent yet disagree on the radius of target space, it follows that the radius is indeterminate between them. Using an analysis of Brandenberger and Vafa (1989), I explain why – even so – space is observed to have a determinate, large radius. The conclusion is that observed, ‘phenomenal’ space is not target space, since a space cannot have both a determinate and indeterminate radius: instead phenomenal space must be a higher-level phenomenon, not fundamental.

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Item Type: Preprint
Additional Information: Based on a paper presented at The Philosophical Foundations of Dualities conference in Physics, University of Florence, September 2014. To appear in a special issue of Studies in the History and Philosophy of Modern Physics.
Keywords: quantum; gravity; duality; string theory; gauge; symmetry
Subjects: Specific Sciences > Physics > Quantum Gravity
Depositing User: Nick Huggett
Date Deposited: 26 Aug 2015 14:51
Last Modified: 26 Aug 2015 14:51
Item ID: 11638
Subjects: Specific Sciences > Physics > Quantum Gravity
Date: 5 August 2015

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