Abstract
String theory predicts that the couplings of nature descend from dynamical fields. All known string-motivated particle physics models also come with a wide range of possible extra sectors. It is common to posit that such moduli are frozen to a background value, and that extra sectors can be nearly completely decoupled. Performing a partial trace over all sectors other than the visible sector generically puts the visible sector in a mixed state, with coupling constants drawn from a quantum statistical ensemble. An observable consequence of this entanglement between visible and extra sectors is that the reported values of couplings will appear to have an irreducible variance. Including this variance in fits to experimental data gives an important additional parameter that can be used to distinguish this scenario from the case where couplings are treated as fixed parameters. There is a consequent interplay between energy range and precision of an experiment that allows an extended reach for new physics.
Highlights
The coupling constants of nature are not truly “constant.” This, at least, is what string theory predicts since such parameters descend from background values of moduli fields, the low energy remnants of higher-dimensional quantum gravity in our four-dimensional (4D) world
Where the factor Hvis denotes everything “other than the visible sector.”. This sort of factorization is well motivated in the context of string constructions since the Standard Model is typically localized on a subspace of the full higherdimensional system, and many extra sectors are sequestered at other locations of the extradimensional geometry
In the previous sections we emphasized that tracing over the extra sector states means that, in general, the visible sector probed by experiment is really in a mixed state, and that there is a statistical ensemble of possible values for the coupling constants
Summary
The coupling constants of nature are not truly “constant.” This, at least, is what string theory predicts since such parameters descend from background values of moduli fields, the low energy remnants of higher-dimensional quantum gravity in our four-dimensional (4D) world. One feature of all known string constructions is that beyond the visible sector there are many additional degrees of freedom These include moduli (see [1,2,3]), as well as large numbers of hidden sectors (see [4]) which may only weakly interact with the visible sector, typically through the mediation of the moduli fields. In making a comparison with experiment, this additional irreducible source of variance will generically produce a different fit to the available data This provides a way to distinguish this scenario from the case where the couplings are treated as fixed parameters
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