# Where we stand-Baez talk at Luminy

1. Mar 13, 2006

### marcus

2. Mar 13, 2006

### marcus

http://math.ucr.edu/home/baez/where_we_stand/
"Fundamental Physics: Where We Stand Today"

"Fundamental" matters seem to be a major focus of attention just now. Probably it is due to some difficulties at the foundation/methodology level---or perhaps the string embarrassment.

Smolin just published "A Crisis in Fundamental Physics" in the New York Academy of Sciences magazine.
http://www.nyas.org/publications/UpdateUnbound.asp?UpdateID=41

Both essays are for general audience, and give historical account of string plight and hep-th doldrums.

Here is how Baez starts off:

"By fundamental physics, I mean the search for a small set of laws which in principle determine everything we can calculate about the universe. The reductionist dream – not always practical, but very seductive.

Where do we stand in the search for these laws? What do we know, and what are the mysteries? Why do many physicists feel stuck?

Let us begin with the story around 1983, ..."

Last edited: Mar 13, 2006
3. Mar 13, 2006

### f-h

Most remarkable about the talk is that it is a stinging critizism of contemporary theoretical physics without actually ever mentioning it.
Rovelli called Baez on that asking wether what he had just presented didn't imply that the theoretical physics of the last 25 years was "junk". To which John baez replied after some hesitation "You said it".

Fabulous talk, if you have the chance to catch John Baez talk about anything at all, go. He's a fantastic speaker.

4. Mar 13, 2006

### marcus

an exchange between two people I respect highly
thanks for the report f-h

5. Mar 13, 2006

Staff Emeritus
Baez attributes the, how shall I phrase it? - stiffness of the string physicists to the usual suspect, pride. But looking at the discussions, and especiallt the comments thread at Not Even Wrong over Smolin's new essay, I suspect there is something that goes deeper. Back to the way physics students are trained, at least in US grad schools.

To learn quantum physics you have to make a leap of faith. You can't really learn it "conditionally"; if you try you'll always be fighting yourself and unable to think freely enough in the field to do good work. You have to accept that quantum physics with all its counterintuitive assertions is to replace common sense physics in your mind and "heart".

Now the teachers have to motivate their students to make this leap, and I think they do it by offering them a deal; buy into QM and we will teach you how the world really works. We may not have that final theory yet, but it exists, and yours may be the generation that reaches it! And the students who go on to work in high energy particle physics accept this and are invested in it to a great and deeply emotional degree.

Other physicsts - those who go into condensed matter physics or especially those in relativity research, don't have anywhere near so much investment in quantum weirdness, although some of the GR physicists seem to have caught some of Einstein's triumphalism (If the experiment disagres with my theory, so much the worse for the experiment).

This really makes for a two cultures split in physics and my point is that it's not about stupid academic politics or such though it entails much of that, it's about the DEARLY BELOVED TREASURE OF THEIR HEARTS.

The last time we had so much rancor in a scientific discipline it was the sociobiology wars between the strong evolutionists and the basically Marxist tabula rasists, and then too, it was about deeply felt and irreconcilable investments of the heart.

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6. Mar 14, 2006

### Chronos

A bit philosphical compared to the usual SA slant on things, but, I agree. Us old people are slow to reach conclusions, but cling to them with tenacity. We live in a causal universe. Despite the success of quantum physics, I think Einstein was closer to the truth . . . God does not play dice . . . at least not the way we cast them.

7. Mar 14, 2006

### f-h

SA, my immidiate reaction was that Baez was talking about String Theory, but upon reflection this is not true, he was talking about everyone. There is new and surprising data from cosmology and by the large the theoretical physics community is ignoring it.
Mostly because nobody seems to have a clue how to handle it...

WRT to the investment in QM or GR I stand with Rovelli:
http://www.edge.org/q2006/q06_9.html#rovelli

"There is a major "dangerous" scientific idea in contemporary physics, with a potential impact comparable to Copernicus or Darwin. It is the idea that what the physics of the 20th century says about the world might in fact be true."

8. Mar 14, 2006

### arivero

f-h, on the contrary, the most cited works last year are the ones about the new results from cosmology, so they are not being ignored. They are even getting new sections in the Review of Particle Properties.

In fact, I would prefer the hep-th and hep-ph communities to forget about these results and to concentrate in particle phenomenology.

As for the rest, I agree that Baez is doing a strong criticism of the (pseudo)mathematization of fundamental theoretical physics, very near to Woit's.

9. Mar 14, 2006

### arivero

World wide problem. Students are trained (actually, selected) to solve problems (and to enjoy it). Not to select problems. When students become Peers, the peer-review system reinforces the mechanism.

10. Mar 14, 2006

### wolram

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11. Mar 14, 2006

### f-h

Arivero, yes people are aware of it, and there is quite a bit of model building being done, but it seems to me that the people working fundamentaly, in String Theory and LQG have no idea how to read this new data for hints of what's going on fundamentaly.

12. Mar 14, 2006

Staff Emeritus
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13. Mar 15, 2006

### Careful

Exactly, and this is the main obstacle to progress in science since we really require NEW physics which goes beyond relativity, QM and how we percieve the other interactions. This is NOT a technical problem as history has proven it:

(a) there exists up to date no theory which unifies electromagnetism with GR - all attempts until now failed (also Kaluza-Klein) - and for a good reason !
(b) QG is really almost nowhere (apart from some technical mumbo jumbo which has been developped in the last 30 years)
(c) We did not properly understand yet - IMO - QED (lots of difficult open problems over there)

Our three most fundamental theories (not only two of them - as is often told) are mutually in conflict with each other. Solving these problems requires young, stubborn PhD students and postdocs which have the liberty to take that risk.

Cheers,

Careful

14. Mar 15, 2006

### Careful

haha, I think SelfAdjoint that you are mistaken: those who cannot accept QM simply have the task to do better (which is possible). I believe that in the end, one will have to be prepared to sacrifice to some extend parts of ALL our cherished theories; and believe me, the damage to QM will be the greatest (although GR will have to go partially out of the window too - cfr problem of cosmological constant).

But one thing is for sure: physics is natural philosopy, a message that has been greatly overlooked in the second part of the 20'th century.

15. Mar 15, 2006

### arivero

Hmm note that the problem is not that they are blocked about new physics and problems, the problem is that they enjoy equally any new physics. If needing to choose, they will choose the one able to generate most interesting problems.

16. Mar 15, 2006

Staff Emeritus

Well certainly this opinion, which grandly dictates what physics may be and do, is pure philosophy! My point is that we know NOTHING about Planck scale physics, and both of our beautiful theories break down there, perturbative quantum physics cannot work there and diffeomorphisms obviously are irrelevant there.

17. Mar 15, 2006

### Careful

Indeed, the more fashionable and flashy the problems are in a so called new´´ approach, the more interest it gains. It is a pitty that most students are not made aware that the deepest and most challanging problems are OLD.

Cheers,

Careful

18. Mar 15, 2006

### Careful

Oh no, you do not need to go to the Planck scale to get into trouble ! As I said, there is no unification between GR and EM, which would have to take place at length scales bigger than the compton length of the particles (10^{-13} metres). And who says that you need to go to the planck scale to unify GR and QM ? No SelfAdjoint, this is not philosophy at all, this is hard reality. Another one : Newtonian gravity gets already into trouble at the submillimeter scale. These problems already require new physics, the planck scale is just a smoke gun in order to give the illusion that we certainly did not make a wrong interpretation of the EXISTING data.

Cheers,

Careful

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19. Mar 15, 2006

### john baez

Actually, a lot of condensed matter physics is based on quantum theory. In classical mechanics, for example, a ferromagnet is strictly impossible - see Feynman's lectures, the section on magnetism. Lots of other phenomena, like semiconductors, superconductors, superfluids, Bose-Einstein condensates, the quantum Hall effect, and quantum dots, are also completely incomprehensible without quantum theory. It's hard for me to imagine a succesful condensed matter theorist who hasn't internalized the principles of quantum theory.

The big difference between condensed matter physics and particle physics is that experiments are a lot cheaper in condensed matter physics, so it's easier to test theories.

20. Mar 15, 2006

### john baez

you said it!

Thanks! I didn't like Rovelli's question, which put me on the spot. I didn't want to say "no, physics is doing okay!" But I didn't want to draw such an extreme conclusion from the difficulties fundamental physics finds itself in.

It's quite possible that in the future, lots of current fundamental physics will be seen as junk. It's possible that lots will be seen as visionary. Only time will tell. Either way, I don't have the right to pass any sort of judgement on other physicists, since I've tried to do better and haven't succeeded.

So, after hesitating, I pointed to Rovelli and said "You said it!"

Of course this was meant as a double entendre, since in some moods I completely agree with his assessment. But I probably should have said something clearer, and less cute.

21. Mar 15, 2006

### Mike2

You could have said, "Perhaps it's good in showing us what NOT to do."

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22. Mar 15, 2006

### john baez

Right. There are more string theorists than any other sort of people working on "fundamental physics", so I focused a bit more on them. But it's not like there are other people out there with a vastly higher batting average when it comes to predicting the crazy new results the astronomers have been finding. As http://magazine.uchicago.edu/0602/chicagojournal/dancing.shtml" [Broken] said at a recent Chicago University talk, “All of these things came from measurements that weren’t predicted.”

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23. Mar 16, 2006

### Careful

I think Feynman was a bit quick in drawing these conclusions, that is about how indespensible and *unique* quantum mechancs is. Sure, there is something lacking in our understanding of EM, which breaks down at the compton scale of particles. However, one does not need quantum mechanics in order to realize that ! There are pleanty of other means to remedy this situation : for example, a compton scale cure of EM seems to make the strong nuclear forces entirely unnecessary. This is the kind of new´´ physics we should be trying out. Personally, I do not understand your attitude: there is virtually no experimental input from gravitation beyond a micrometer (actually one could safely claim that gravitation does not even *exist* there ), we know that EM fails for atomic physics, we know that quantum physics cannot retrieve macroscopic realism (as Legett calls it) without some MWI ghost stories, logically QM and GR are incompatible and the consequences of QM and EM are far from being properly understood. Still (!), you say that in order to become a succesfull physicist, you have to live with the contradictions and just work in your branch (sadly you are right) of interest and not bother about the rest. I thought you were a person working on *fundamental* physics :uhh: ...

My point is that there are pleanty of alternatives one could try out to match current empirical results. The *real* problem being that any such attempt is instantenously met with criticism like : oh but I believe you can reproduce these and these QUANTUM results, but can you also do that and that?´´. When I started my physics studies, it was because I thought that people were *genuinely* interested in looking for a coherent world picture; sadly I must confess that I was wrong - the self protection mechanism being : useless publications.

You say: it is impossible to understand superconductivity, superfluidity etc classically. True, if you do not change classical laws on the compton scale, this is indeed the case (you can also make your theory fundamentally stochastic like in SED, but that does not put you any further in solving the cosmological constant). However, if you ask any expert in condensed matter physics how it works, he/she will give you a *realist* explanation using new compton scale physics. Actually, as far as I know, any new physical effect (like bose-einstein, fractal quantum Hall effect) has been conceived by what you might call semiclassical arguments. Isn't that funny, we think in a realist way and still we give birth to exclusive´´ quantum effects :-)) Hence, ....

Cheers,

Careful

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24. Mar 16, 2006

### marcus

BTW Baez just dropped in at Christine Dantas blog
http://christinedantas.blogspot.com/2006/03/quantum-gravity-and-standard-model.html [Broken]
scroll to the nexttolast comment (around #32)
this is off-topic but folks in this thread (Baez talk at Luminy) might be interested in what he says in his comment on Christine's thread about
Quantum Gravity and the Standard Model
(the Smolin paper about braid SM)
pardon the interruption

Last edited by a moderator: May 2, 2017
25. Mar 16, 2006

### CarlB

I'll put my two cents in on what is wrong with physics.

Far from QM having a background issue, I think that relativity went off track when Einstein eliminated the ether and universal time. To appreciate my stance on this requires that you read the following two papers which give a flat space formulation for gravity:

<b>Gravity, Gauge Theories and Geometric Algebra</b>
Lasenby, Doran and Gull
http://www.arxiv.org/abs/gr-qc/0405033
Phil. Trans. R. Soc. Lond. A 356, 487-582 (1998).

The reason I think the above is a step in the right direction is that it makes it so much easier to deal with real problems, for example the charge held near a black hole, discussed in the above.

David Hestenes' comments on the above are here:
http://modelingnts.la.asu.edu/pdf/GTG.w.GC.FP.pdf [Broken]
http://modelingnts.la.asu.edu/pdf/SpacetimeGeometry.w.GC.proc.pdf [Broken]

But I am pretty much alone in thinking that the primary problem in QM is the vacuum. To appreciate this requires reading Schwinger's book, Quantum Kinematics and Dynamics. That, and a little Clifford algebra, will convince you that unphysical gauge freedom in the standard model arises from an unphysical (i.e. mathematical) splitting of the density matrix formalism into bras and kets. Along that line, note that in 2000, Brown and Hiley extended Bohmian mechanics to density matrices and liked it better than the regular Bohmian mechanics:

http://www.arxiv.org/abs/quant-ph/0005026

Another way of putting this same complaint: The original sin in QM was the factoring of the Banach space to a Hilbert space. Not that it is something that cannot be done, the problem instead is that it can be done in too many ways. The result is that the public is convinced that when you rotate an electron 360 degrees it is somehow multiplied by -1. In the density matrix formulation, this nonsense is avoided.

Carl

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