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« How Smart Are Other Animals, Really? | Main | Who Believes in ESP? »



The End of Strings (for now)

Those seeking a fresh, inside look the string brouhaha should check out the post of my colleague Jim Weatherall on the blog of the Center for Science Writings. Jim just got a masters in physics from Harvard (after getting a bachelor's in philosophy--perfect preparation) and knows some of the pluckers there, including appealing Lisa Randall and appalling Lubos Motl. Jim’s post has already provoked responses from, among others, Peter Woit, author of Not Even Wrong, my interview with whom you can also find on our site (Jim filmed us). If that’s not enough string stuff for you, come watch me debate The End of Science with the string enthusiast Michio Kaku October 18 at Stevens. This will be my last post on string theory for a while. To paraphrase Jim, this pathetic excuse for a theory has gotten much more attention than it merits. Upcoming posts will address more credible endeavors, such as parapsychology.

Comments

nigel cook

‘It always bothers me that, according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of space/time is going to do? So I have often made the hypothesis that ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed, and the laws will turn out to be simple, like the chequer board with all its apparent complexities.’

- R. P. Feynman, Character of Physical Law, November 1964 Cornell Lectures, broadcast and published in 1965 by BBC, pp. 57-8.

Nothing works because of a mathematical model which so-and-so invented to describe something in the natural world. For example, until quantum gravity is included in general relativity, the latter won't even be a complete mathematical model for gravity, let alone the cause for all gravitational phenomena.

You might as well claim that that people meet and marry because of the equation 1 + 1 = 2.

Underlying general relativity, there are real dynamics. If it is analogous to a Yang-Mills quantum field theory, exchange radiation will behave differently in the universe than in an atom or nucleus, due to redshift.

Smolin et al. show in LQG that a path integral is a summing over the full set of interaction graphs in a Penrose spin network. The result gives general relativity without a metric (ie, background independent). Next, you simply have to make gravity consistent completely with standard model-type Yang-Mills QFT dynamics to get predictions:

(1) Over short distances, any Yang-Mills quantum gravity will be unaffected because the masses aren’t receding, so exchange radiation won’t be upset.

(2) But over great distances, recession of galaxies will cause problems in QFT gravity that aren’t physically included in general relativity.

I don’t know if gauge boson’s are redshifted with constant velocity or if they are slowed down due to recession, being exchanged less frequently when masses are receding from one another.

It doesn't matter: either way, it’s clear that between two masses receding from one another at a speed near c, the force will be weakened. That’s enough to get gravity to fade out over cosmic distances.

This means G goes to zero for cosmology sized distances, so general relativity fails and there is no need for any cosmological constant at all, CC = 0.

Lambda (the CC) -> 0, when G -> 0. Gravity dynamics which predict gravitational strength and various other observable and further checkable phenomena, are consistent with the gravitational-electromagnetic unification in which there are 3 dimensions describing contractable matter (matter contracts due to its properties of gravitation and motion), and 3 expanding time dimensions (the spacetime between matter expands due to the big bang according to Hubble’s law). Lunsford has investigated this over SO(3,3):

http://www.math.columbia.edu/~woit/wordpress/?p=128#comment-1932:

‘... I worked out and published an idea that reproduces GR as low-order limit, but, since it is crazy enough to regard the long range forces as somehow deriving from the same source, it was blacklisted from arxiv (CERN however put it up right away without complaint). ... my work has three time dimensions, and just as you say, mixes up matter and space and motion. This is not incompatible with GR, and in fact seems to give it an even firmer basis. On the level of GR, matter and physical space are decoupled the way source and radiation are in elementary EM. ...’ - D. R. Lunsford.

Nobel Laureate Phil Anderson:

“... the flat universe is just not decelerating, it isn’t really accelerating ...”

- http://cosmicvariance.com/2006/01/03/danger-phil-anderson


Hence Lunsford's model is right. Note that this PRECEDES experiment. I got a publication in Electronics World Oct 96, which is for a dynamical model.

When you think about it, it’s obviously correct: GR deals with contractable dimensions describing matter, and one time dimension. Lunsford simply expands the time to three dimensions hence symmetry orthagonal group (3,3). The three expanding time dimensions give the cosmological recession! The Hubble expansion then becomes a velocity variation with time, not distance, so it becomes an acceleration.

Newton’s laws then tell us the outward force of the big bang and the inward reaction, which have some consequences for gravity prediction, predicting G to within experimental error.

We already talk of cosmological distances in terms of time (light years). The contractable dimensions always describe matter (rulers, measuring rods, instruments, planet earth). Empty space doesn’t contract in the expanding universe, no matter what the relative motion or gravity field strength is. Only matter’s dimensions are contractable. Empty spacetime volume expands. Hence 3 expanding dimensions, and 3 contractable dimensions replace SO(3,1).

Lunsford's paper:

http://cdsweb.cern.ch/search.py?recid=688763&ln=en

I'd be keen for you to ask Peter Woit about Lunsford, and also about Woit's use of representation theory to generate the Standard Model in low dimensions. This is the really big problem if gravity is successfully modelled by Lunsford's approach.

Wikipedia gives a summary of representation theory and particle physics:

‘There is a natural connection, first discovered by Eugene Wigner, between the properties of particles, the representation theory of Lie groups and Lie algebras, and the symmetries of the universe. This postulate states that each particle “is” an irreducible representation of the symmetry group of the universe.’

Woit’s historical approach in his course notes is very clear and interesting, but is not particularly easy to read at length on a computer screen, and ideally should be printed out and studied carefully. I hope it is published as a book with his arXiv paper on applications to predicting the Standard Model. I’m going to write a summary of this subject when I’ve finished, and will get to the physical facts behind the jargon and mathematical models. Woit offers the promise that this approach predicts the Standard Model with electroweak chiral symmetry features, although he is cautious about it, which is the exact opposite of the string theorists in the way that he does this, see page 51 of the paper (he is downplaying his success in case it is incomplete or in error, instead of hyping it).

Lunsford's paper on gravity: http://cdsweb.cern.ch/search.py?recid=688763&ln=en

Woit's paper producing the Standard Model particles on page 51: http://arxiv.org/abs/hep-th/0206135

Maybe you can find out why these ideas are being neglected by string theorists!

Try to get a rational and reasonable response from Lubos Motl, Jacques Distler, Sean Carroll (who is not a string theorist but a cosmologist, so he should be willing to make a comment on the cosmological effects of Lunsford's paper - the end of the cosmological constant in particular), and also Clifford Johnson who is a string theorist.

Since the string theorists have been claiming to have the best way to deal with gravity, it would be interesting to see if they will defend themselves by analysing alternatives, or not.

(I predict you will get a mute reaction from Woit, but don't let him fool you! He is just cautious in case he has made an error somewhere.)

nc

BTW, I tried to shut down string theory in the Oct. 2003 issue of Electronics World, but discovered that there is a lot of public support for string theory, because string theorists and (fellow travellers like Hawking) have had sufficient good sense to censor viable alternatives, including Lunsford's paper from arXiv even after it was published in a peer-reviewed journal.

nc

Thanks for keeping the comment above! I've now got some dialogue from string theorists Prof. Jacques Distler and Ass. Prof. Lubos Motl, which is a step in the right direction.

On Prof. Clifford Johnson's blog, Prof. Jacques Distler replied to my question regards the compatibility of Lunsford and superstring:
http://asymptotia.com/2006/10/16/manifold-yau/#comment-2156

Because Lunsford has 3 orthagonal time dimensions (describing basically empty, non-contractable, expanding volumes of space) and 3 orthagonal contractable distance dimensions (describing matter like rulers, hence if you want to measure the distance in empty space and use a ruler then you are not actually measuring the space you are measuring contractable matter - ie the ruler), and unifies GR and electromagnetism in the limit where the cosmological constant disappears, it's evident that to preserve supersymmetry you would need a 4-d Calabi-Yau manifold.

Jacques says the 4-d Calaib-Yau is just a single thing called a K3 manifold, which Wiki says is: "the second simplest compactification after the torus. Compactification on a K3 surface preserves one half of the original supersymmetry."

Next, Lubos says:

http://www.haloscan.com/comments/lumidek/116109989645197647/#626354

Dear NC,

according to the normal definitions, a higher number of time dimensions than one implies the existence of closed time-like curves that violate causality and allow you to convince your mother to have an abortion before you're born, which is a contradiction, using the terminology of Sidney Coleman.

That's one of the problems with Danny Ross Lunsford's 3+3D theories as well as all other theories with two large times or more.

Even if the signature of the Universe were 7+3, you would have to compactify or otherwise hide 4+2=6 dimensions to get realistic physics.

Jacques is right that all 4-real-dimensional Calabi-Yau manifolds are homeomorphic to a K3 manifold: it's a proven theorem. The only other smooth topology, if you have a more tolerant definition of a CY manifold, would be a 4-torus.

The possible Ricci-flat geometries on a K3 manifold form a 57-real dimensional moduli space isomorphic to SO(19,3,Z)SO(19,3)/SO(19) x SO(3). All of the solutions are continuously connected with each other. ...

All the best
Lubos
Lubos Motl | Homepage | 10.17.06 - 5:26 pm | #


The claim that 3 orthagonal time dimensions can form closed loops is naughty of Lubos, since it is implicitly ruled out by the dynamics of the model. The 3 time dimensions are the orthagonal dimensions of empty and expanding space between masses, so they can't form closed loops. The 3 distance like dimensions describe the dimensions of matter which is non expanding and indeed contractable.

In conventional superstring theory, there are 10-d and to make that work with a 4-d GR you roll up 6-d into the Calabi-Yau manifold. Hence for Lunsford's 6-d GR unification, you would need to roll up only 4-d.

This is totally different to the Kaluza-Klein [pseudo] 5-d unification where you have 1 extra distance dimension rolled up. Lunsford is adding two extra time dimensions, not two extra distance dimensions.

I'm not sure that supersymmetry is correct. The usual role of it in getting rid of UV divergences due to massive loops and unifying everything near the Planck energy scale, is extremely extravagant since it postulates an unobserved superpartner for every observed partner, and can't predict anything checkable about the superpartners (such as their exact energy, etc.). I think a lot can be done to understand unification by working at the problem the other way, and asking questions about the conservation of gauge boson energy when the electromagnetic field is attenuated by vacuum polarization above the IR cutoff. That energy presumably goes into creating short range nuclear forces via vacuum dynamics. If so, that would predict unification automatically because when say EM force becomes very much stronger at higher energy (closer distance) due to less vacuum polarization separating the observer from the particle core, the amount of attenuated force causing nuclear forces will start to decline because there is less attenuation of EM to provide the energy to power strong nuclear interactions. Hence, perfect unification should occur anyway, just on the principle of conservation of energy in gauge boson fields.

However, I could be wrong about this. Pauli used energy conservation with a beta decay "anomaly" to predict the neutrino. Bohr used the same anomaly to argue that energy conservation fails to work in beta decay, and at first dismissed Pauli's prediction as speculative. However, Bohr was wrong. See http://cosmicvariance.com/2006/10/03/the-trouble-with-physics/#comment-124189

The comments to this entry are closed.



   
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