Arcadian Functor

occasional meanderings in physics' brave new world

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Marni D. Sheppeard

Monday, October 26, 2009

Multiverse Mania

Matti Pitkanen points out that any reasonable quantum cosmology involves a multiverse, in some sense. Unfortunately, the word multiverse is too widely used in the painfully ludicrous context of stringy landscapes and the Dark Force, and this classical geometry essentially defines its meaning. If AF ever lapses into some strange use of the word, without clarifying its meaning, then you have permission to swear in the comments section.

It is quite difficult to figure out which multiverse advocacy group is the most impossible to forgive. Certainly the so called theoretical physicists are high on the list. But are the philosophers any less guilty? At least the physicists have the excuse that they were never required to take courses in the history and philosophy of science and, in true 20th century camaraderie, were rewarded for playing the game and forgetting about the problems that they were actually supposed to solve.

A professional philosopher of physics, on the other hand, should be able to dismiss the objective, observer independent multiverse with three words that they learned in kindergarten: I am thinking, therefore I exist. Descartes, and many others, must be turning in their graves, to see science so debased.

10 Comments:

Blogger Mitchell said...

"A professional philosopher of physics, on the other hand, should be able to dismiss the objective, observer independent multiverse with three words that they learned in kindergarten: I am thinking, therefore I exist."

I am thinking, therefore I exist, therefore there is no multiverse? I don't get the last step.

October 27, 2009 6:11 PM  
Blogger Matti Pitkanen said...

A non-technical manner to state the last step is that every thought re-creates the multiverse since multiverse plus thought is not the same thing as the multiverse.


A more refined manner to say this requires some ideas about consciousness. One must accept "free will" (not too difficult for me and everyone denying it in philosophical discussion believes free will in everyday life). TGD inspired detailing of the argument would go as follows.

Let us believe that the counterpart of elementary particle in quantum consciousness theory is moment of consciousness identified as quantum jump replacing the quantum multi-verse (super-position of classical deterministic worlds in geometric sense) with a new one.

Also every conscious thought is the act of recreation so that the notion of observer independent multiverse (and also universe) does not make sense.

October 27, 2009 9:09 PM  
Blogger nige said...

"... of classical deterministic worlds ..."

Hi Matti,

I just wonder what your thoughts are concerning the fact that Poincare chaos exists in classical physics unless the universe only contains two objects?

Poincare discovered that the three (or more) body orbit problem only behaves deterministically in classical theory if you can ignore one or treat two as one, and thus reduce it to effectively a two body problem. The solar system has evolved stability over a long time and its determinism rests upon the fact that the sun's mass way exceeds the mass of all the planets put together. So it approximates as a two ody problem for any planet: just that planet and the sun determine essentially all of the gravitational force present.

In the atom, the Coulomb attraction works on charge, and unlike gravitational charges in the solar system, the electron carries the same electric charge as the proton. Therefore, electrons interact and deflect one another to a great extent in atoms, causing Poincare chaotic indeterminancy. Even in the hydrogen atom where there is just one (real) electron, you have virtual pairs of fermions randomly appearing in different geometric configurations around it where the electric field is strong enough for spontaneous pair production. These virtual fermions interact with the electron, deflecting its orbital motion at random.

You don't need a multiverse to explain subatomic chaos. That comes about in first quantization, e.g. Schroedinger and Heisenberg QM, which is contradicts relativity and is hence wrong, as everyone should be aware of, except QM teachers and stringy theorists.

October 27, 2009 10:32 PM  
Blogger Matti Pitkanen said...

Hi Nige,

as you say quantum multiverse is of course realized already in hydrogen atom.

About Poincare chaos. You probably mean with non-determinism inability to calculate the predictions in finite time. Equations of motion as such are deterministic.

Finite measurement resolution means that both classical and quantum chaos is tamed by finite measurement resolution which might be also seen as a characteristic of physical states rather than only of our knowledge about them.

I must confess that I was purposefully a little bit sloppy when I spoke about classical deterministic worlds. In TGD framework classical determinism is not complete. This is the key aspect of the basic variational principle and due to its huge vacuum degeneracy mathematically highly analogous to the gauge degeneracy of Maxwell action. Now however different "gauges" are physically inequivalent and the situation is physically analogous to spin glass degeneracy but in 4-D sense. Space-time surface decomposes to deterministically behaving regions. The interpretation is as a classical space-time correlate for the non-determinism of quantum jump sequence.

October 28, 2009 2:40 AM  
Blogger Matti Pitkanen said...

Hi Nige,

as you say quantum multiverse is of course realized already in hydrogen atom.

About Poincare chaos. You probably mean with non-determinism inability to calculate the predictions in finite time. Equations of motion as such are deterministic.

Finite measurement resolution means that both classical and quantum chaos is tamed by finite measurement resolution which might be also seen as a characteristic of physical states rather than only of our knowledge about them.

I must confess that I was purposefully a little bit sloppy when I spoke about classical deterministic worlds. In TGD framework classical determinism is not complete. This is the key aspect of the basic variational principle and due to its huge vacuum degeneracy mathematically highly analogous to the gauge degeneracy of Maxwell action. Now however different "gauges" are physically inequivalent and the situation is physically analogous to spin glass degeneracy but in 4-D sense. Space-time surface decomposes to deterministically behaving regions. The interpretation is as a classical space-time correlate for the non-determinism of quantum jump sequence.

October 28, 2009 2:41 AM  
Anonymous Rob Taylor said...

I'm with Mitchell - how do you justify this step?

October 29, 2009 2:35 AM  
Blogger Kea said...

Mitchell and Rob, the logic is really the other way around. The landscape multiverse is an ugly idea, not worthy of consideration.

Ask yourselves: what is Real? Until the early 20th century, nobody knew that other galaxies existed. We looked out at the stars and thought the universe was filled with stars. Only through observation did we eventually grant galaxies the great honour of Existence.

It has always been this way in science. The first thing I can know, is that I think ... I observe. What does it mean to posit other universes that have no influence on our observations? In what sense can they ever be Real?

October 29, 2009 9:48 AM  
Blogger Matti Pitkanen said...

Still a comment about "What does it mean to posit other universes that have no influence on our observations?". I agree. "No influence on our obervations" is the point. Without quantum multiverses replaced by new ones in quantum jumps there would no Descartes with his thoughts.

Hardly no one resists the notion of electron's wave function. By replacing point-like electron with 3-dimensional surface you have multiverse as a quantum superposition of space-time surfaces.

October 29, 2009 2:43 PM  
Blogger Mitchell said...

"What does it mean to posit other universes that have no influence on our observations? In what sense can they ever be Real?"

Anthropic reasoning which is not just about self-consistency (we couldn't exist at all unless X existed), but which is probabilistic (in most universes where observers exist, X exists), seems to require either that the other universes exist, or that the unique actual universe is regarded as a random sample of the possible universes. To put it another way: anthropic explanations are explanations in terms of typicality in the multiverse - this is an average universe, or an average universe-with-observers. So for such an explanation to be valid, either all the universes actually exist, or the unique actual universe is a random sample from a set of merely possible universes which all had a certain a-priori probability of actually existing.

You can eliminate a multiverse from anthropic explanation, but only at the price of supposing this "random sample" theory of what gets to be actual.

I think Lubos is sensible with respect to anthropic explanation. One should keep looking for non-anthropic explanations for as long as possible, but if they don't exist, there is no inherent problem with the anthropic option.

October 31, 2009 6:05 PM  
Blogger nige said...

Hi Matti,

Thank you for the explanation about the connection of determinism to the TGD framework.

Nige

November 07, 2009 5:39 AM  

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