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See here.

Did Pasti review Tegmark's essay laugh

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No, Pasti did not review Tegmark's paper. :p .

But have you tried to read it? To me it looks very much like a very early (and incomplete) draft of a much, much longer review article.

And in this form, indeed I am not surprised it was rejected (I sill need to figure out what "dishonorable mention" means). I would have sent it back to the author with a request to complete and develop the draft, and I do not believe that you would have recommended for publication either.

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BTW, Ibliss, are you comming to Potsdam?

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Hi Pasti,

Yes, the paper reads like a summary of his ideas he has written about in other papers. He didn't elaborate on the level 4 multiverse (the idea that ''mathematical existence = physical existence'') at all.


I'm not going to the LQG conference. I have too many other things to do...

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"Dishonorable mention" is just Tegmark having fun. It received an honorable mention, I think. A nice overview of the "everything" issue, IMHO.

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Do you guys take Tegmark seriously?

I have a hard time believing he isn't engaging in a race to the ridiculous.

Math, at least as understood today, can posit a huge number of possible universes. He seems to be drawn to the most fanciful and least proveable.

That something can exist may equal that it does exist. But that doesn't make it the 14 or so light-year bubble in which we, specifically, exist.


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Tegmark's ideas are interesting. Sure, you can't directly observe objects that are outside the horizon, about 13.7 billion lightyears away or for that matter events in parallel universes.
Any theory, including Tegmark's, will be tested on predictions about things we can observe. Tegmark's point is that multiverse theories can predict certain parameters that would otherwise could be unexplainable. In a recent article he has given an anthropic explanation for neutrino masses.


It is actually wrong to picture yourself in one place in the multiverse. The critcism against Tegmark that since the rest of the multiverse is not observable, it can't matter isn't correct for this reason. In a (typical) multiverse setting there are an infinite number of copies of you. You can't say that you are at one given place, because the all the knoweldge you have about yourself, your surroundings etc. doesn't pin you down in a unique place in the multiverse.


If you now consider a quantity that isn't well known yet, such as the neutrino masses, then you have to picture yourself distributed over all possible values of these unknown quantities. The value of neutrino masses determines the evolution of galaxies and hence influences the probability that life can evolve per cubic lightyear. Since you are distributed over all possibilities you'll have more copies living in a situation where this probability is larger. This then allows you to calculate a probability distribution over the possible neutrino masses.

Tegmark's mathematical approach isn't very satisfactory because he is vague about the prior probabilities.

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I take Tegmark very seriously. His theory has no free variables and is the simplest possible, and thus to be preferred over all others by Occam's Razor. All other theories ultimately suffer in that they have no answer to the "why this rather than that?" question, which makes them ultimately incomplete.

Even without Tegmark, there is now strongly suggestive evidence that some sort of Multiverse exists (anthropic principle, cosmic coincidences, Everett, string landscape, etc). Tegmark's Everything is computationally the *simplest* possible multiverse.

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Count wrote:
"Tegmark's point is that multiverse theories can predict certain parameters that would otherwise could be unexplainable."

Actually it doesn't. Tegmark's ideas predict nothing of substance. They are no more capable of telling us why a Planck's width is a Planck's width than why Pi is 3.1415926....

What Tegmark dose, in my opinion, is excuse our ignorance by providing a framework that says ... every possibility exists so these must too. Big deal. Even my cat could have come up with that one. And with far less math.


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Jonathan wrote:
"All other theories ultimately suffer in that they have no answer to the "why this rather than that?" question, which makes them ultimately incomplete."

I'll not argue that other theories are woefully incomplete. But Tegmark's bullet is fired so wide that I can argue that in some universe there MUST be an invisible purple rhinoceros. Heck I can even posit that in some universe Jesus Christ is actually my personal saviour, that Noah built a big boat, and that dinosaurs make the best stand-up comics. In Tegmark's view all of them are possible and therefore, given infinite possibilities, must be true somewhere.

I think in this particular universe Tegmark has taken a bit too much LSD. Hey and if not in this one in another one: Right? He explains nothing. He excuses everything. In Tegark's universe there is some place where pigs can fly and Snow White was really kissed by a prince. Impressive physics? I think not.


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Quote:
Originally posted by DA Morgan:
Count wrote:
"Tegmark's point is that multiverse theories can predict certain parameters that would otherwise could be unexplainable."

Actually it doesn't. Tegmark's ideas predict nothing of substance. They are no more capable of telling us why a Planck's width is a Planck's width than why Pi is 3.1415926....

What Tegmark dose, in my opinion, is excuse our ignorance by providing a framework that says ... every possibility exists so these must too. Big deal. Even my cat could have come up with that one. And with far less math.
I disagree that only trivial predictions can be made, see e.g. here .

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I'm not saying that only trivial predictions are made by Tegmark. I'm saying no predictions are made.

Look at this waffle:
"It is argued that small values of the neutrino masses may be due to"

May be due to. What nonsense. "MAY." Now that's predictive of nothing.


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Quote:
Originally posted by DA Morgan:
I'm not saying that only trivial predictions are made by Tegmark. I'm saying no predictions are made.

Look at this waffle:
"It is argued that small values of the neutrino masses may be due to"

May be due to. What nonsense. "MAY." Now that's predictive of nothing.
You are wrong. The word ''may'' is only used to indicate that the assumption of no other reason is made. So, if some fundamental theory doesn't impose significant constraints on neutrino masses then the AP will force them in the range of 1 eV.

This proves that (nontrivial) predictions can be made using the AP.

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If you believe Tegmark can predict the value of any one physical constant from first principles. Please provide the name of the constant, the value predicted, and the source of the information.

I've never seen one but am willing to be corrected.


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Quote:
Originally posted by DA Morgan:
If you believe Tegmark can predict the value of any one physical constant from first principles. Please provide the name of the constant, the value predicted, and the source of the information.

I've never seen one but am willing to be corrected.
Why not check out the Phys. Rev. D article on neutrino masses?

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I did. I don't see anything predicted from first principles. If you do please enlighten me.

Again I ask:
"Please provide the name of the constant, the value predicted, and the source of the information."


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Quote:
Originally posted by DA Morgan:
I did. I don't see anything predicted from first principles. If you do please enlighten me.

Again I ask:
"Please provide the name of the constant, the value predicted, and the source of the information."
A nontrivial range of the neutrino masses is predicted. To make more precise predictions you need to develop the multiverse theory more. This is done here:


http://arxiv.org/abs/hep-th/0509184


My point is that this is a well motiveted area of research and has nothing to do with Tegmark being high on drugs, as you have suggested.

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I asked for the second time:
"Please provide the name of the constant, the value predicted, and the source of the information."

Your response:
"A nontrivial range of the neutrino masses is predicted"

This is nonsense and you know it. I can predict a non-trivial value for pi too: So what. Predicting from first principles that the value will be 3.1415926... is quite another matter.

What you have basically said, above, is that Tegmark has not predicted nothing of substance which substantiates my original statement that there is nothing there except smoke and mirrors.


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Quote:
What you have basically said, above, is that Tegmark has not predicted nothing of substance which substantiates my original statement that there is nothing there except smoke and mirrors.
That's not true. First of all, Tegmark's ideas are falsifiable, because a priori Tegmark's calculation could have been in conflict with the range of masses favoured by neutrino oscillations observations. The value of the neutrino masses could e.g. still be consistent with our exixtence, but they would have made the experimental constraints a-typical.


Second, accepting the validity of his approach, one learns more about neutrinos. He makes the prediction that the sum of the masses is 1 eV, and this was not known.

Another anthropic prediction was made by Hoyle a long time ago. He predicted that unless the carbon nucleus has an energy level just above the ground state carbon could not have formed in stars in significant abundances. I think that he actually predicted the value of the energy level correctly, but I'll have to look that up.

Hoyle's prediction was very impressive but in a certain sense trivial. Because the prediction follows from the fact that we exist. But Tegmark goes further than that and he predicts a confidence interval. So, although we could still exist if neutrino masses were totally different than the prediction, that would be unlikely in the multiverse setting.

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DA MOrgan:

But Tegmark's bullet is fired so wide that I can argue that in some universe there MUST be an invisible purple rhinoceros. Heck I can even posit that in some universe Jesus Christ is actually my personal saviour, that Noah built a big boat, and that dinosaurs make the best stand-up comics. In Tegmark's view all of them are possible and therefore, given infinite possibilities, must be true somewhere.

I think in this particular universe Tegmark has taken a bit too much LSD. Hey and if not in this one in another one: Right? He explains nothing. He excuses everything. In Tegark's universe there is some place where pigs can fly and Snow White was really kissed by a prince. Impressive physics? I think not.
_____________________________________________

I can imagine a modern astronomer attempting to explain to a natural philosopher a few hundred years ago that not only are all the stars you can see suns like our own, but that there are actually billions more in our galaxy that we can not see; and not only our galaxy, but billions of others galaxies each with billions of stars. The response would likely be identical to yours "I think not", followed by "what are you smoking?". But that wouldn't make it not so.

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