A What Does Prof Krauss Mean About False Vacuum Decay and Cosmology?

[Trollfaz]

I just want to know what Prof Lawrence Krauss really meant in his article Late time behavior of false vacuum decay: Possible implications for cosmology and metastable inflating state. I recently got the wrong impression that humans are destroying the universe by looking at it. Can someone please explain what he is really trying to say?

 

[Chalnoth]

Do you have a link so that we can see precisely what you're talking about?

 

[Trollfaz]

https://arstechnica.com/uncategoriz...gy-may-shorten-the-life-span-of-the-universe/

https://arxiv.org/abs/0711.1821

 

[Chalnoth]

Skimming the paper, I'm not entirely sure what they're trying to say with respect to observers. It sounds like they wrote a paper about quantum vacuum decay, and then tacked on a blurb in the abstract and discussion about how this might relate to the impact of observers, without ever quantifying that impact.

It sort of sounds like they're trying to apply the Quantum Zeno effect to cosmology. The idea there being that if you have an experimental apparatus to measure a decaying system rapidly enough, the system fails to decay (or at least decays much more slowly than if it isn't continuously measured). This effect has been experimentally observed.

But I don't see how this effect can apply to quantum vacuum decay. The issue is that the above experiments don't just involve some scientist looking at results: they're actually creating interactions with the decaying system in question in order to determine whether or not it decayed. By contrast, all of our measurements of dark energy are highly indirect, and don't depend upon us building any experimental apparatus that has a meaningful impact on anything far from Earth's orbit. We're not, for example, shining bright lasers around the galaxy in order to perform astrophysical observations.

 

[Bandersnatch]

Have you read Krauss' comments in the thread I linked to in response to your earlier question?
Here it is again:

I have decided that indeed the final two sentences of the paper left the incorrect impression that causality was somehow involved. The purpose of these comments was to refer to work I have been discussing with Alan Guth related to this paper.. namely to what extent cosmological observations made today constrain the nature of the wavefunction and our quantum state in a way that may imply we are not in the late-decaying phase.. This is what I should have said, rather than leaving the incorrect impression that somehow actually making the measurement has a causal effect.. it does not.. it merely constrains our quantum state.. The new version of the paper with the last two sentences changed removes this ambiguity I hope, for all future journalists who look at it.

L. Krauss

 

[Trollfaz]

Ok, I guess that he wishes to say that any observations on the universe narrows its number of possible states into 1

 

[Trollfaz]

I m sorry i have to revive this thread, but i still can't figure what he's really saying

 

[Chalnoth]

I m sorry i have to revive this thread, but i still can't figure what he's really saying

In his clarification, he's saying that observations place limits on the possible ways the universe can be. For a simple example, if we observe that a clear sky is blue, then any model that would predict a different color of a clear sky would have to be wrong: whatever the laws of physics are, they must allow for a blue sky, since that's what we see.

I'm really not sure precisely what that has to do with this paper, since it's an extremely general statement to make.

 

[Trollfaz]

Thx