From Peter Woit at Not Even Wrong:
Back in 2013 one could read lots of claims in the media that “Hard evidence for the multiverse” had been found, based on “effects of quantum entanglement between our horizon patch and others”. These claims were discussed on this blog (with a response from the authors here). A new paper by Will Kinney has now been published in JCAP, including the following conclusion about such claims:
It is worthwhile to discuss in general the “concrete predictions” originally claimed by the authors of refs. [1,2], since several key claims do not survive even cursory scrutiny. For example, the discontinuity in the effective potential claimed to be correlated with voids and the CMB cold spot does not appear to in fact exist: for all physically relevant values of the parameters V0, λ, and b, the modulation F(φ) is a smooth function, with no characteristic discontinuities which would explain features in the power spectrum. Perhaps more importantly, the form of the effective potential resulting from landscape entanglement is completely dependent on the choice of inflationary potential V(φ), which is itself an arbitrary free function. One could just as consistently choose the underlying inflationary potential in the absence of landscape corrections to be the same as the effective potential (2.7)! In this sense, the landscape model is no more (or less) predictive than single-field inflation itself, and most of the claimed predictions of the entanglement model turn out not to have been predictions at all. However, any considerations of theoretical consistency are a moot point: even if one takes the claimed predictions at face value, almost all of them are ruled out by Planck. Experiment always supersedes theory, and the model does not match the data.
This paper has an unusual story behind it, with an author of the work it criticizes trying to keep it off the arXiv. For more about this, see here and here. More.
It’s hard for some of us to understand what’s “unusual” about an attempt to suppress the paper. Evidence for a multiverse actually need not be valid; it need only feel right.
Increasingly, the multiverse is believed without evidence because it avoids the implications of the evidence for fine-tuning of the universe. New Scientist is a good place to see this view unpacked.
Essentially, “no evidence” beats evidence if naturalism is at stake.
See also: Cosmic coincidences?: New Scientist says multiverse is best explanation!
The war on falsifiability in science continues
Evolution bred a sense of reality out of us
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