We Don't Need No Stinking Theory Of Everything!

This is a Q&A with Lisa Randall.

The reason why I'm highlighting this is that the questions being asked is the type of questions many of us faced with we talk to the public. The very first question, for example, is rather typical:

Doesn't every physicist dream of one neat theory of everything?

Of course not! But the public has a very narrow idea of what physics is. Many are surprised when I tell them that the largest percentage of physicists in the US are working in the area of condensed matter/material science, which is not the first of study that directly involves the Higgs, high energy physics, string, etc. So for many of us, this "theory of everything" isn't something we dwell on that much, not to mention, there are even prominent physicists who think that this "theory of everything" is a myth.

In any case, this article covers some of the common questions that we often see.

Zz.

More Really Is Different

I've mentioned before, many times in fact, on here about the issue regarding reductionism and "The Theory of Everything". I argued that a large fraction of practicing physicists, especially those in condensed matter physics, do not buy into this idea of a theory of everything, simply based on emergent phenomena that we observe in condensed matter physics.

The main "poster child" for such argument is Phil Anderson's "More Is Different" paper published quite a while back. Now comes a paper that strengthen Anderson's assertion that More Really Is Different.

Gu et al.[1] published a paper in which, using the 2D Ising model that simulates a cellular automata of magnetic spins.

Abstract: In 1972, P.W. Anderson suggested that ‘More is Different’, meaning that complex physical systems may exhibit behavior that cannot be understood only in terms of the laws governing their microscopic constituents. We strengthen this claim by proving that many macroscopic observable properties of a simple class of physical systems (the infinite periodic Ising lattice) cannot in general be derived from a microscopic description. This provides evidence that emergent behavior occurs in such systems, and indicates that even if a ‘theory of everything’ governing all microscopic interactions were discovered, the understanding of macroscopic order is likely to require additional insights.

A News and Views in Nature[2] this week article reviewing this paper explains it a little bit clearer for those of us not familiar with these 2D computation and the intricacies of cellular automata.

In their study, Gu et al. mapped the dynamics of a certain CA into the lowest-energy (ground) states of Ising models. In this framework, Figure 1 can now be interpreted as a snapshot of a two-dimensional spatial lattice of spins. They grouped spins into blocks that encode the logic operations needed to produce universal computation in the corresponding CA. They then defined the 'prosperity', p, of two-state systems as "the probability that a randomly chosen cell at a random time step is live" (live meaning state 1).

Using the computational properties of the CA, Gu and colleagues were able to show that p is undecidable for infinite, periodic Ising systems. They argued that, as a consequence, many macroscopic properties of an Ising system, including the system's magnetization and degeneracy (number of independent configurations) at zero temperature, depend on p and hence are also undecidable. Because Ising models have been used to describe not only magnetic materials but also neural activity, protein folding and bird flocking, the consequences of Gu and colleagues' results transcend both computer science and physics.

Nice stuff! This would be another compelling argument against reductionism and the fallacy of the "Theory of Everything".

Zz.

[1] M. Gu et al., Physica D: Nonlinear Phenomena, v.238, p.835 (2009). Also see the arXiv version here.
[2] P.M. Binder Nature v.459, p.332 (2009).

A Different Universe: Reinventing Physics from the Bottom Down

I have mentioned many times on the issue of emergent phenomena, why the so-called Theory of Everything may be nothing more than a TOE for reductionism, and the arguments put forth by Robert Laughlin regarding this. I have also highlighted his book on such emergent phenomena.

An excerpt of this book is one of the essay on PhysicsCentral. So if you haven't read it yet, this might give you a "flavor" on what he is tackling. I wish they had done a longer excerpt, because the issue of collective behavior and emergent phenomena are only covered in the final paragraph. I believe is PNAS paper and his Nobel Prize speech have a lot more "teeth" in his argument.

In any case, you should really read the whole book if you haven't come across such argument before.

Zz.

Public Lecture: A Different Universe

Hey, if you are anywhere near the UC-Davis campus on May 21-22, you may want to attend this. I certainly would if I were in the neighboorhood.

Nobel Laureate Robert Laughlin will be giving a public lecture based on his book. And it is about time too. This lecture should be a suitable antidote to the glut of public exposure on String Theory and the other notions of the "Theory of Everything". I have mentioned earlier about several of Laughlin's papers on the fallacy of such a notion and how reductionism has been unable to even come close to describing several emergent phenomena that we observe today. This type of message is seldom heard of especially among the general public, and certainly not among the pseudoscience proponents who don't seem to be aware of it. Hopefully, Laughlin's lecture will be one of the means to spread this message around.

I am certainly doing my part in it... :)

Zz.

The Theory of Everything?

There have been frequent claims, both from legitimate sources and quackeries, of the possibility of finding something called the Theory of Everything (TOE). Supposedly, such a theory would contain ALL the necessary interactions that would be able to, in principle, describe ALL the phenomena (at least the existing ones) that we have observed.

We won't talk about the quackery aspect of this. The legitimate aspect of the belief in a TOE is due to the fact that there are only 4 fundamental interactions that are responsible for all the phenomena in our universe that we know of: gravity, electromagnetic, strong, and weak interactions. There is a strong belief (and desire) that all 4 of these fundamental interactions can be unified into a single consistent description. Already the electromagnetic and weak interactions have successfully been unified into an electroweak theory. There are every indication that the strong interaction will be next. Gravity might be the last and most difficult. However, assuming that it can be unified with the others, one then have what is called the Grand Unified Theory (GUT). Most people claim that then, we have achieved the TOE.

The implicit assumption in making such a claim that GUT = TOE is that the principle of Reductionism works. Reductionism is a philosophy which, to state rather crudely, everything in the universe can be reduced to the basic interaction at a single particle case. Then, by simply adding a higher level of complexities, one can then recover all the other more complicated, macroscopic phenomena. So if you know all the interactions that an atom in a human skin has, then by including more and more of the number of atoms/molecules, you will eventually be able to describe all the properties of the human skin. Hence, once you know all there is to know at the single particle scale, then everything else is just a matter of complexities. This then leads to the notion that GUT = TOE.

Most particle and high energy physicists espouse this point of view. I would single out Steven Weinberg as the prominent champion of this school of thought. String theoriests have also been known to slip up now and then by claiming that unification of gravity with quantum mechanics is a step towards GUT and TOE.

However, there is another school of thought that would contradict the idea that GUT = TOE. This school of thought is made up of condensed matter physicists, which make up the largest percentage of practicing physicists. The most prominent condensed matter physicists who have stated their opposition to the reductionists idea are Phillip Anderson, Robert Laughlin, and David Pines. They brought up examples that are described as "emergent" phenomena, often seen in condensed matter. These are phenomena that only occurs, or can only be defined, when there are a gazillion interactions occuring. Examples of these are superconductivity, fractional quantum hall effect, magnetism, etc. Laughlin, for example, argued that if you try to write down all the interactions of a single electron in a conductor, no matter how many electrons you add up in your interactions, you will NEVER recover the superconductivity phenomenon. Superconductivity is an emergest phenomenon that is a result of a many-body interaction. The starting point in describing such a phenomenon MUST start not from a single particle scenario, but from a many-body ground state scenario. This effect emergers out of a many-body interaction and will simply disappears if one tries to take it apart to a single-particle level.

What this boils down to is the claim that GUT is the TOE for reductionism, not the TOE for physics. Anyone claiming the existence of any form of TOE will have to seriously address the glaring omission of a huge body of phoenomena from condensed matter physics, which holds some of the most highly verified observations with the highest degree of certainty in any field of physics.

For more resources on emergent phenomena from condensed matter physics and why they contradict the claim of GUT=TOE, read the references below:

1. http://www.pnas.org/cgi/reprint/97/1/28.pdf
2. http://www.pnas.org/cgi/reprint/97/1/32.pdf
3. http://arXiv.org/abs/hep-th/0210162
4. R.B. Laughlin, Rev. Mod. Phys., v.71, p.863 (1999).
3. P. Anderson, Science v.177,p.4 (1972).

Zz.