B-mode CMB Fluctuations and Quantum Gravity

Most recent answer: 04/01/2014

If the vortex-like patterns recently discovered in the CMB turns out to be really produced by primordial gravitational waves, will that help us in our search of a quantum gravity theory since these gravitational waves were produced very shortly after the Big Bang?
- Anonymous

When those results were first published, the standard interpretation was that the fluctuations were actually a blown-up version of the quantum zero-point fluctuations in the gravitational waves. So that would have confirmed that gravity indeed should be incorporated into the quantum framework, as almost all of us believed beforehand. It turns out that the background of other fluctuations, just from background crud, had not properly been subtracted. So we'll have to wait to see if any such quantum gravitational wave signature exists.

Even if one is found, however, rthat would fall a bit short of providing guidance for just how that unified quantum gravity theory will look. Thus the basic properties of these expected fluctuations were calculated  just by assuming that gravity is quantized, but without any consideration of what the deep theory of quantum gravity actually is.  So there's no guarantee that observations of this sort will be of much help in pinning down such a theory.

Mike W.

(published on 04/01/2014)

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