Many Worlds in One: The Search for Other Universes. Alex Vilenkin, Author. Hill & Wang $24 (p) ISBN Many Worlds in One has ratings and 20 reviews. John said: I’m not sure who is the better scientist, but in terms of the prose required to address thi. RENOWNED cosmologist Alex Vilenkin, who is director of the Tufts University Institute of Cosmology in Massachusetts is known for his theory.

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It contains various amusing anecdotes, especially about Alan Guth. Sean Carroll is credited with the following story:. One of the leading superstring theorists, Joseph Polchinski, once said that he would quit physics if a nonzero cosmological constant were discovered.

Polchinski realized that the only explanation for a small cosmological constant would be the anthropic one, and he just could not stand the thought. He also describes the reaction to his anthropic arguments back during the years when these were not all the rage like they are now:. First, we will need to map the landscape. What kinds of vacua are there, and how many of each kind? We cannot realistically hope to obtain a detailed characterization of all 10 vacua, so some kind iin statistical description vikenkin be manyy.

We will also need to estimate the probabilities for bubbles of one vacuum to form amidst another vacuum. The we will have all the ingredients to develop a model of an eternally inflating universe with bubbles inside bubbles inside bubbles… Once we have this model, the principle of mediocrity can be used to determine the probablility for us to live in one vacuum or other.

Unfortunately for this research program, it has yet to even begin to get off the ground, and there are very good arguments that it can never succeed. There are an infinite number of possible vacua, and trying to make this finite so one can do statistics requires putting in cutoffs, with results then strongly depending on the cutoff.

Alsx large numbers of these vacua make any attempts to identify ones that agree with the real world computationally completely intractable. Even if one could do this, all evidence is that one would end up with broad statistical distributions for many of the parameters of the standard model, providing no kn prediction of what new experiments will see, or any insight vilnkin why these parameters have the values that they onw.

Look on the bright side, Peter. They have solved all our problems.

In the immortal words of Alyosha Zamolodchikov when asked what he thinks of strings as the final theory of everything. As for straightforward debunking, Abraham Loeb has presented an observational test to show that the CC is not of anthropic origin:. Existing technology enables to check whether planets form in nearby dwarf galaxies and globular clusters by searching for microlensing or transit events of background stars.

If planets are as common per stellar mass in these descendents as they are in the Milky Way galaxy, then the anthropic argument would be weakened considerably since planets could have formed in our Universe even if the cosmological constant was three orders of magnitude larger than observed.

Loeb disposes of any a priori argument that the CC is anthropically determined, since it is plausible that habitable zone planets will be detected in the descendents of dwarf galaxies this is what he proposes searching for which would rule out an anthropic CC, as he explains. One has every reason to expect to find evidence of planet formation in dwarf galaxies just as one finds it in our own galaxy. Loeb has taken care of that.

And Steinhardt has proposed a mechanism by which, in his cyclic scheme, the CC value could be explained. The original Weinberg mechanism never really worked.

The anthropically-favored value of the CC depends on the prior distribution of magnitude of density fluctuations. We were not the only ones to notice this….

The anthropic principle has been proposed as an explanation for the observed value of the cosmological constant. Here we revisit this proposal by allowing for variation between universes in the amplitude of the scale-invariant primordial cosmological density perturbations. We derive a priori probability distributions for this amplitude from toy inflationary models in which the parameter of the inflaton potential is smoothly distributed over possible universes.

## General Relativity and Quantum Cosmology

We find that for such probability distributions, the likelihood that we live in a typical, anthropically-allowed universe is generally quite small. MathPhys, your vilenki reminds me of a remark of Stalin: Chris W, Your comment on my comment explains many things to me. Keep the immortal sayings of wise Russians coming, please.

You can alx anthropic arguments for the number of dimensions of space — where the possible values are integers — but surely any anthropic argument applied to a continuous-valued constant will still yield an uncountable infinity of allowable values? Hoyle realised that for the observed amounts of C, there must be a resonance at 7.

### Many Worlds In One | Not Even Wrong

However, perhaps it was because of the anthropic principle. I think the cancer of corruption in physics is that in default of real understanding, obfuscation is preferred. String theory and its landscape are the ultimate obfuscation with which to sink any questions anyone asks about physics. When exactly was it that crackpotism won?

Do you ever just feel like giving up and embracing the extra dimensional multiverse? It is so much easier to be a crackpot, peter! Hoyle showed that other mechanisms would not work. For our universe to exist people etc there had to be a resonance in C, and he calculated its energy correctly. Observations confirmed his claim. Hence, for cars to exist, the roads must possess very constrained, predictable features.

Unless you really have something new to say, please resist the temptation to start rehashing various aspects of the anthropic principle every time the landscape gets mentioned here. At this point, all this is doing is adding to the noise level. One part of the story is that he wants to put a bound on the volume of the compactification manifold, arguing that if it is too big, we would see its effects already i.

This kind of bound together with othersallows him to argue that possibly the number of vacua given by various flux compactification constructions is finite because the size of the manifold grows as you add fluxes. One problem with putting in a cutoff though, is that, even if you make the number of vacua finite, the distribution of them may be peaked near the cutoff lots more ways to put in fluxes at the maximal number of them.

He seems to have given up on this, partially because of this problem.

People who talk about statistical calcuations of these vacua possibly providing predictions are just ignoring the fact that this idea has vjlenkin tried, and now is dead for a good reason.

I am not a regular Times reader. Any help with finding it? Unlike many articles in the may full of hype about extra dimensions, etc. Anybody shot in the back? Dennis Overbye is an editor at the NYT.

What other qualifications does he have to comment on the current state of particle theory? Given that he understands that physics is an experimental science driven by the discovery of new data, Overbye already more qualified to comment on the current state of particle theory than many string theorists. Is ST getting workds SA?

What about Glashow, who in a just world would along with Coleman be senior guru of Harvard Physics, but, due to his views of superstring theory, had to go to Boston U.

I wonder what Clavelli was thinking when he wrote these papers.

From the present to the past. Moreover, string theory does not favour any particular universe over another, which is not a good state of affairs as we clearly live in a universe with a particular set of physical properties.

People who talk about statistical calcuations of these vacua are just ignoring the fact that this idea has been tried, and now is dead. The Statistics of Supersymmetric D-brane Models http: We have performed a vast computer survey worldd solutions to the stringy consistency conditions and present their statistical vilenkon with special emphasis on the frequency of Standard Model features. Among the topics we discuss are the implications of the K-theory constraints, statistical correlations among physical quantities and an investigation of the various statistical suppression factors arising once certain Standard Model features are required.

We estimate the frequency of an MSSM like gauge group with three generations to be one in a billion. Benni, What is dead is the idea of extracting any physical predictions out of such calculations. There are no predictions in the papers you mention. This papers are the reason why Douglas has given up counting vacua.

He referes in his talk at Solvay directly to Luests work. The Idea of counting vacuas is not death, it was solved. However one could say the chance of 1 over a Billion to find the standard model is a prediction! But then we have the case that at the end, one has a certain possibility in string theory to describe our world.

Since no one can find the solution explicitely because of Douglas Complexity paper I think it is indeed fair to say the whole subject is at its end.

Once we have this model, the principle of mediocrity can be used to determine the probablility for us to live in one vacuum or other.

The point why I send you these papers was, that I think this program has succseeded in the papers from Luest! The answer is one over a billion! Home Frequently Asked Questions. Sean Carroll is credited with the following story: He also describes the reaction to his anthropic arguments back during the years when these vilen,in not all the rage like they are now: This entry was posted in Uncategorized.

July 2, at 4: Hi, as a plot-inclined person, I would be soooo happy to see a graphical description of just one of the 19 parameters of the standard model as a function of any one of the possible needed cut-offs that allowed a kne principle to work out… That would be a start.

July 2, at 6: July 2, at 8: Hsu, Alejandro Jenkins, Mark B. July 2, at July 3, at 4: July 3, at 5: July 3, at 9: July 3, at All, Unless you really have something new to say, please resist the temptation to start rehashing various aspects of the anthropic principle every time the landscape gets mentioned here.

July 3, apex 6: July 4, at 3: July 4, at 9: