Monday, July 30, 2007

Lubos Motl wrote:

"George Chapline just gave the most provoking and most bizarre colloquium we have seen at Harvard for years. (I guess that the talk would not be bizarre enough for Quantoken and perhaps not even for Arun, and I apologize if they will be disappointed by the amount of strangeness.) Chapline used to be a T.A. for Feynman's lectures, he was awarded by various awards, but his goal right now is to revolutionize our understanding of the strong gravitational fields.
In other words, Chapline did not like the idea about the horizon being a regular place in space. He did not explain how he wants to modify the laws of physics in such a way that his new critical behavior replacing the horizon suddenly turns on. He also sketched his condensed matter system where the speed of sound goes to zero and asked what happens. Bert Halperin answered but my guess is that during his next lecture, Chapline will repeat his remark that no one at all the famous universities he will have visited knew the answer ...
The causal structure is guaranteed by the rules of special relativity that have been tested in detail - and for which there are no good reasons to violate them in a drastical way. And the temperature and the entropy were first calculated by Hawking who followed Bekenstein, but then they were also reproduced by completely independent methods from the microscopic counting of string theory - a calculation that was definitely not guaranteed to give the same results but it did. That is a pretty strong double argument.
Someone asked whether Chapline's new picture of the black hole also requires one to alter the membrane paradigm by Kip Thorne, in which the horizon is viewed as a superconducting membrane, and the answer was that the speaker did not know what the paradigm was.

A particular example of the application of "emergent phenomena" beyond the realm of their validity was the attempt to explain gravity as an emergent phenomenon based on some spin-2 bound states of quasiparticles near the Fermi liquid - the type of work that was done by Zhang and others. In reality, the existence of such bound states was never really justified, and if there were any evidence that such bound states could have existed, such arguments would have allowed not only for the spin-2 "gravitons" but also for higher-spin particles that simply should not exist.

There are many theorems that show that gravity can't be constructed in one way or another, that the interactions are incompatible with higher-spin gauge symmetries, and all things like that. Such no-go theorems are sometimes circumvented by string/M-theory, but it always involves a non-trivial feature of string/M-theory that was not anticipated before and that violates some of the more or less hidden assumptions.

All these vague arguments about gravity being constructed as a solid state system only existed at the level of free particles and there were never hints that the interactions of these particles shall reproduce general relativity. Given the fact that the very reason for introducing gravity is that it is an interaction, the failure to reproduce the interactions is pretty serious.

But even a priori, is there any reason to believe such pictures and pursue them? I think that the primary motivation for such attempts is to satisfy our old instincts that everything, including the most mysterious objects such as those in high-energy physics and quantum gravity, must eventually be "made" of the things we know from the everyday life such as water, wine, bread, and butter.

These objects are macroscopic, slow, low-energy, and with the exception of wine, they are also predictable and deterministic.

In my humble opinion, this approach may be good to entertain ourselves and our non-physics friends, but it is a misguided approach to theoretical physics - and I don't mean just fundamental physics right now but any physics that transcends our everyday lives - simply because theoretical physics has become less intuitive and more mathematically abstract, and it had to be so. And it will be so in the future. And it is one of the symptoms of a true conceptual progress. The humans have been trained to comprehend phenomena associated with classical, non-relativistic, low-energy physics - and it should not be unexpected that the intuition fails if we try to understand quantum, relativistic, high-energy, unusual phenomena that go beyond the realm of validity of our naive approximations."

Lubos Motl also allegedly wrote in

The Reference Frame:
Steven Weinberg vs weird physicists: torsion

The most important events in our and your superstringy Universe as seen from a
conservative physicist's viewpoint
Saturday, March 03, 2007 ... /////

"Steven Weinberg vs weird physicists: torsion
A reader has pointed out the following exchange between Steven Weinberg and
Friedrich Hehl in the new issue of Physics Today. If you've never heard about
the latter, you're not the only one. For our purposes, it suffices to know that
this Gentleman has written down many meaningless theories of gravity with an
extra torsion tensor. They have no relevance for experiments and they have
nothing to do with the most important advances in physics of the last 100 years
or so.

Hehl offers some religious, scientifically meaningless statements or loud
screams why the torsion tensor is needed or why it is special, citing some
physically irrelevant sources from the early 1920s. Weinberg of course gives the
only answer that a sane physicist can give: the torsion tensor is just another
tensor field - one that isn't needed for any symmetry, consistency, or beauty -
so if there is no experimental reason why it should be added, and surely there
is no such reason today, it won't be added. Period."

I, Jack Sarfatti rebut Motl: Everything Lubos says here is simply false. Three good references showing Lubos statements to be false are
1. L. O' Raifeartaigh "The Dawning of Gauge Theory", Princeton 1997 Ch. 2, & Ch 10 on Utiyama 1956 locally gauging rigid SO(1,3) to get part of general relativity. Actually what Utiyama got was the torsion-induced curvature beyond Einstein's 1916 theory, but no one realized it at the time.

2. J. C. Taylor "Gauge Theories in the Twentieth Century" 3.1 "Gravity as a gauge theory" T.W.B. Kibble "Lorentz invariance and the gravitational field" J. Math Phys 2 (1061) 212-21 shows that Motl simply does not understand the facts. Kibble showed that when you locally gauge the full RIGID 10 parameter Poincare group of 1905 special relativity you get Einstein's theory generalized by Cartan to include torsion fields as well as curvature fields. Einstein's 1916 torsion-free theory is what you get when you locally gauge only the 4-parameter translation group. This gives the non-trivial part of the 4 tetrad 1-forms as the compensating "Yang-Mills" type compensating gauge potentials (Levi-Civita connection for parallel transport is bilinear in the tetrads and their gradients). When you, in addition, locally gauge the 6-parameter Lorentz group you also get 6 dynamically independent spin-connection 1-forms as compensating potentials giving ultimately the contortion tensor used in theories like Hehl's, Hammond's, Kleinert's et-al. Note 1916 GR T4 only gives curvature-only spin-connections that do not have torsion gaps.

3. Hagen Kleinert's work

"part from the above, the book presents the general differential geometry of defects in spaces with curvature and torsion and establishes contact with the modern theory of gravity with torsion." - Kleinert

Lubos Motl continues

"Weinberg as a relativistic heretic

The origin of this controversy goes back to the 1970s. Weinberg's textbook on
general relativity was very modern - and oriented towards the interpretation of
general relativity as a part of the effective quantum field theory - as it
presented the metric tensor as another field in spacetime whose local symmetry
happens to coincide with the diffeomorphism symmetry but it is just a technical
detail: interacting spin-two fields simply must have gauge symmetries that
reproduce diffeomorphisms. Because of that, we can interpret the whole theory as
a theory of curved space but we don't have to: the metric tensor may also be
viewed as another field living in the Minkowski spacetime or, equivalently - by
symmetries - any other spacetime that you might imagine to be your starting
point. You don't need to know the words "curved space" to calculate the
predictions of general relativity."

(Jack Sarfatti) This is simplistic as can be seen from Feynman's Lectures on Gravitation and Roger Penrose's work on the "nonlinear graviton".

The point is that you do not get the full power of GR for strong fields until you sum an infinity of Feynman diagrams based on the globally flat Minkowski background. This is non-analytic (Ken Wilson) "More is different" (PW Anderson) emergence like in the BCS theory of superconductors. Sure you can do post-Newtonian first order perturbation theory using flat spacetime background, but you will never get horizons.

For example, in SSS solution, the flat background is

g00 ~ 1 - 2GM/c^2r

only in the limit 2GM/c^2r << 1

BTW Puthoff makes a similar error in his PV theory. Dicke never meant his 1961 model to be used beyond the above approximation.

Lubos: "A certain group of people in cosmology has reacted just like religious bigots
and they wanted Weinberg to "retract" these statements whose validity is
completely obvious to anyone who has any idea how field theory - especially
quantum field theory - works."

Jack: Lubos completely misses the point here.

Lubos: "However, the deeper you penetrate into the
community of the loop-quantum-gravity-like pseudoscientists and their fans, the
less clear these things are to them. Weinberg has never retracted but I think
that it is fair to say that these loud irrelevant fourth-class scientists have
intimidated Weinberg into silence which is kind of scary."

Jack: So, Lubos thinks Roger Penrose, Stephen Hawking, Kip Thorne, John Wheeler, Charles Misner are "fourth class"?
Lubos has shifted here from physics to polemics.

Lubos: "Unification vs segregation

Those people think exactly in the opposite way than a theoretical physicist
should. Theoretical physicists want to unify the laws of Nature. They want to
understand an ever greater set of phenomena using theories with an ever smaller
number of independent assumptions and parameters. Gravity is a manifestation of
something that we can call spacetime geometry - but all of physics may be viewed
as a manifestation of some "generalized geometry". There is no fundamental gap
between gravity and other fields. There is only one world whose parts constantly
interact. Any attempt to separate the world into two parts - geometry and matter
- is bound to be an approximation or worse. All of these objects in field theory
are just some tensors that are coupled according to some rules."

Jack: Too vague to be useful. However, the fact that gravity is simply Yang-Mills theory applied to the Poincare group rather than internal groups does do what Lubos yearns for here, but the price is the torsion field that Lubos says is crackpot physics! Lubos is hoisted by his own petard! My own polemics. ;-)

Lubos "In fact, string theory shows that the metric tensor field and the matter fields
arise in the very same way from more fundamental ingredients."


ds^2 = e^aea = guvdx^udx^v

e^a is the Einstein-Cartan tetrad 1-form

Lubos "What's important for these interactions is whether they respect some crucial
symmetries and whether they lead to self-consistent predictions that are finite
and whether these predictions can be successfully compared to experiments. We
also want the number of independent parameters - the total number of all
coefficients of terms that can be added without modifying the symmetries - to be
as small as possible so that the theory's predictivity is as large as it can be."

Jack: Cliche. Sure. So what else is new?

Lubos: "Regardless of words, the most general interactions between your tensors must be

Jack: Cliche. Sure. So what else is new?

Lubos: "Everything else is just religious nonsense. You may try to guess other
principles or ideas how the theory should look like that can lead you to the
right theory if you're lucky. But they don't have to. You can't consider your
own idiosyncratic beliefs to be an argument for your approach before any other
material evidence - either theoretical or experimental - for your theory

Jack: Polemical ranting.

Lubos: "What about the torsion? Torsion is a hypothetical part of the Christoffel
connection that is antisymmetric in the lower two indices. In conventional
general relativity, the symmetric connection is derived from the metric tensor
and its torsion is simply zero. This is the grand theory that has been
successfully tested. The three-form H-field in many vacua of string theory may
be viewed as some kind of torsion. It's because the conditions for an unbroken
supersymmetry include the term proportional to the H-field in a way that is
analogous to the old papers that discussed torsion together with spinors."

Jack: Obviously Lubos has no knowledge of Kibble's 1961 paper. He is making something simple overly complicated. So like a string theorist! :-)

Lubos: "Other fields in string theory

But if you don't know this "torsion" jargon, you don't lose anything. The
two-form B-field and its exterior derivative, the H-field, are just other
examples of fields in the effective field theory. They have some couplings and
some gauge symmetries and string theory predicts all of them, up to field
redefinitions that can, of course, always be made. It is somewhat misleading to
use the word "torsion" because we can't really say that all objects are affected
universally by the background fields. It is more usual that we interpret the
H-field as a generalization of the electromagnetic field than a kind of a
torsion tensor. And we have good reasons to do so.

For example, charged objects are also influenced by non-gravitational gauge
fields. In the presence of matter, it is no longer true that the geometry knows
everything about the natural motion of objects in a general situation. We need
other fields, too. Once we accept that there are other fields, we must consider
the most general set of rules controlling these degrees of freedom that are
consistent with the given symmetry and consistency principles. In particular,
the torsion is just another tensor and it is not true that its couplings are
completely determined. All contractions of indices etc. are legitimate a priori.

The statements that the dogmatic torsion is necessary because of [some
incoherent principle] are completely dumb."

Jack: An ignorant remark for reasons stated above.

Lubos: "Torsion is not necessary simply
because the theories we have don't include any torsion, they are
self-consistent, and they moreover agree with experiments."

Jack: That 96% of the stuff of the universe is not atoms and photons etc MAY PERHAPS be the smoking gun for torsion fields. Also maybe the Pioneer anomaly. Indeed dark energy and dark matter are the elephant and the 800 gorilla in the room.

Lubos; "It is plausible that
a more complete theory would predict new fields but these fields must be
massive, otherwise they would contradict observations. For example, the
three-form H-field in four-dimensional string-theoretical vacua may be
Hodge-dualized to a one-form which is a gradient of a scalar field called the
universal axion. This particle may or may not exist but it must be massive,
otherwise it would induce new forces that are not observed.

Irrational pressures

At any rate, the idea that there are some additional aesthetic conditions in
field theory that tell you that you should include fields that are otherwise
clearly unnecessary or conditions that tell you that you shouldn't allow some
interactions of some fields just because you want to use some name for these
fields is analogous to astrology. Nothing like that can be used in science. Such
new ideas could only become valid if you showed that they are necessary for some
kind of new symmetry, or that they must arise from an underlying high-energy
theory. At the sociological level, I am flabbergasted how the people who
understand physics and contributed to physics at a rate below 0.1% of Steven
Weinberg are self-confident when they try to intimidate him."

Jack: Again Lubos is obviously not aware that locally gauging the Poincare group in same way as internal groups gives curvature + torsion Einstein-Cartan theory. All we need is the battle-tested local gauge principle applied to the rigid spacetime symmetries of global special relativity and you cannot avoid torsion in addition to curvature.

Lubos: "Einstein's flawed attempts

In the last decades of his life, Einstein used to think about many unified
theories. He thought that only gravity and electromagnetism were real:
everything else was supposed to miraculously emerge from the approach. So he has
tried all the silliest theories you can imagine - for example, an asymmetric
metric tensor whose antisymmetric part describes F_{mu nu}. Torsion was another
example. The greatest mistake of Einstein was his inability to accept the
probabilistic nature and predictions of quantum mechanics. But the unjustified
attempts to "extend" the metric tensor in order to cheaply include
electromagnetism may be viewed as the second greatest blunder of his life.

For example, if we imagine that the metric tensor is not symmetric, we are still
allowed to split it into the symmetric and antisymmetric part. These two parts
can be treated separately: they can have different interactions. If you treat
them separately, you are still able to satisfy all principles of your field
theory. The Lagrangian is locally Lorentz-symmetric and the full action is
diffeomorphism invariant if you do it right. An action written in terms of an
asymmetric tensor could "look" shorter than a general action describing the
action for the symmetric part and the antisymmetric part but Nature never cares
whether something "looks" shorter. For example, the action of eleven-dimensional
supergravity is not really "short" but it is the most symmetric gravitational
low-energy field theory that exists. It is symmetry and rigidity, not the
length, that matters in physics. The crackpots won't ever get this point."

Jack: Note Lubos use of "crackpot" - overkill, too broad a brush - a bad habit he picked up from John Baez who Lubos thinks is a crackpot for pushing L. Smolin's loop theory approach to quantum gravity. Rovelli is also a crackpot in Motl's black book. Lubos accepts 11D supergravity theory as some kind of Holy Revelation. Sir Roger Penrose then becomes a "crackpot" in Lubos's lexicon for his critique of extra dimensions in "The Road to Reality" for example.

Luubos: "The same comment applies to torsion. If you consider an asymmetric Christoffel
connection, you are still allowed to break it into pieces, i.e. irreducible
representations of the Lorentz group or "GL(4)", and to add different
interactions for these pieces. For diffeomorphism invariance, the symmetric part
will be equivalent to what you get from a metric tensor, and the antisymmetric
part is just another tensor field. There can't be any natural unification here."

Jack: Blatantly false as shown by Kibble cited above.

Lubos: "If your action looked simple in terms of an asymmetric metric tensor or an
asymmetric connection, it would be a pure coincidence. You would still have to
consider all possible deformations of this theory - in which the interactions of
the parts differ - to be equally valid candidates to describe reality.

Horizons and the geometric intuition

Is there something in GR that you can't derive by assuming that the metric
tensor is just another tensor field on some background - e.g. the Minkowski
background? Well, GR predicts the existence of spacetime topologies and causal
diagrams that differ from the Minkowski spacetime. Are they possible? Well,
almost certainly. But still, their existence is compatible with the
interpretation of the metric tensor as another field. The geometric intuition
just gives you a good tool to deal with some singularities: for example, you may
find that the black hole horizon is a coordinate singularity and you can
continue your physical laws to the interior of the black hole. You can see that
there is nothing special happening near the black hole event horizon."

Jack: Again false as shown by Feynman for example.

Lubos: "But this conclusion also follows from a careful analysis of field redefinitions
that are helpful to understand physics near the black hole horizon. These field
redefinitions are nothing else than diffeomorphisms,"

Jack: which are simply the local gauge transformations in going from rigid T4 to local T4(x).

Lubos: "and by making the geometry
look smooth near the event horizon, you obtain a natural hypothesis what should
happen when you cross the horizon: namely nothing."

Jack: True in GR, but not true in Chapline's replacement of GR,

Lubos: "Experimentally speaking,
we're not quite sure. We will never be sure unless the whole planet falls into a
black hole which is not the best collective career move.

It can still be true that you die when you hit the black hole horizon. But the
required laws would violate locality and causality - principles whose precise
form is influenced by non-zero values of the spin-two tensor that we happen to
call the metric. These principles are valuable. The dogma about the existence of
torsion is not an independently valuable physical principle and Weinberg has
always been 100% right when he rejected irrational arguments to include such
"principles" into science.

And that's the memo.

Update: Dean of crackpots

I was also told that the dean of crackpots has written about this exchange."

Jack: Who is that pray tell?

Lubos: "The dean himself offers several characteristically absurd comments attempting to
paint Steven Weinberg as the owner of extreme opinions. Steven Weinberg is one
of the people who have defined the mainstream of particle physics for more than
30 years.

In the discussion, some people including Sean Carroll and Moshe Rozali correctly
say that one must include all terms in the Lagrangian that are consistent with
given symmetries. The dean himself argues that "he understands the effective
field theory philosophy", but in order to instantly show that he doesn't, he
says that he is unconvinced because quantum field theories should be valid at
all energies. QCD is and N=8 SUGRA may also be, so why not. Well, he's just too

Whether or not these theories are well-behaved in the UV can't change the fact
that new physics must surely enter at the conventional 4D Planck scale or
earlier, for example because our world includes gravity. Our world can't be a
pure QCD as the famous apple demonstrates. With gravity, all these theories are
only effective field theories. Even in the case of N=8 SUGRA, the supergravity
description itself is clearly incomplete non-perturbatively because it can't
reproduce poles from the black hole intermediate states.

In the debate with Sean Carroll at the beginning of the debate, the dean shows
that he clearly doesn't understand that the torsion is just another tensor and
its couplings are not determined. It's just amazing how incredibly ignorant this
person is - a person that has been chosen by dozens of journalists to talk big
about physics."

Who is Lubos talking about?

Here Lubos's Polemic/Physics ratio is singular. ;-)

Lubos: "Crackpot Tony Smith tries to spin some - already bizarre - statements by Paul
Ginsparg who has conjectured that Steven Weinberg has "renounced his views". The
similarity of their language with the medieval catholic bigots is clearly
causing them no pain whatsoever. As an argument supporting the opinion that
Weinberg has "renounced" his views, they say that Weinberg likes extra
dimensions in string theory which are geometrical in nature. Well, that's nice
that they are geometrical but the low-energy field theory in 10D is just another
field theory with some tensors, and so is its decomposition in the form of the
four-dimensional effective field theories. In all cases, it is Weinberg's rules
of physics that are important, not pre-conceived opinions about "geometry".

All of string theory may be viewed as a certain generalization of geometry. The
real question is how exactly the right generalization works. ;-) There's no
doubt that string theory has already refined our notions about geometry - by
topology-changing transitions, mirror symmetry, T-duality and so on. If we want
to answer the question what is the right form of geometry in Nature, we must
isolate the right physics arguments and calculations instead of attaching silly
stickers "geometric - good" and "non-geometric - bad" to different ideas. If you
choose any set of axioms or ideas that are called "geometry" at a given moment,
you are never guaranteed that Nature is going to satisfy them. The previous
sentence has been proved many times in the history of physics. It is She who
decides, not you.

Another "wise man" called Eugene Stefanovich argues that Weinberg also has
non-orthodox views on quantum field theory because he starts his derivation of
the theory from particles which makes fields less fundamental. Last semester I
have largely followed Sidney Coleman's QFT I notes that start from particles,
too. What's exactly non-orthodox about it? All these concepts - including fields
and particles - are ultimately parts of the overall picture. There is no
God-given algorithm telling you what you should start with when you learn or
teach these things. Any attempt to pretend that such a God-given algorithm
exists is religious bigotry, not science. Every particle physicist who thinks
that particles are not important in particle physics is deeply confused.
Moreover, even if Coleman and Weinberg were the only two physicists who followed
this approach, which they're not, it would no longer be a fringe pedagogical

Why do we neglect higher-derivative terms

Peter Woit also completely misunderstands why we neglect higher-derivative terms
in various theories such as the Dirac theory or general relativity. He argues
that we must start with minimal couplings and boldly make predictions to avoid
being not even wrong. But this approach is the obsolete perspective of the
1920s. Today, a physicist who understand her field would certainly not argue in
this way. The reason why the higher-derivative terms (e.g. higher powers of
curvature in general relativity) are not that important is that they are
higher-dimension operators whose effects decrease faster as you go to longer
distances: every derivative adds a 1/L factor to the typical size. The operators
with many additional derivatives are called irrelevant perturbations and it is
the most relevant ones that dominate the long distance physics. You can always
choose sufficiently long distance scale so that the irrelevant operators will
become as unimportant as you wish. There is no other rational justification to
eliminate the higher-derivative terms - in fact, one can't completely eliminate
them at all without contradicting the rules of the renormalization group flow.
Even if the higher-derivative operators were absent at one scale, you generate
them if you flow into another scale. They can't be absent universally.

Because Peter Woit argues that one should study "simple" theories of this kind
because they are "beautiful" proves that his sense of "beauty" is based on ideas
that have been known to be inconsistent with the laws of quantum mechanics for
more than 30 years and he clearly can't understand anything important from the
last 30+ years of particle physics. Beauty can no longer be measured in this
obsolete Woitian way. It is no longer possible to truncate theories in this way.
There is nothing special about the "minimal" theories he likes to think about.
At the quantum level, one can't really define such minimal theories at all.

There's just far too much organized influence terrorizing people in science.
Whenever your results or conclusions of your work disagree with a sufficiently
large group of ignorants, they will attack you personally in the worst possible
ways and hire unwise journalists who do the same in the media. They will present
the fact that your results reject their preconceptions as your moral flaw."

Jack: Let He who is without Sin cast the first stone. Seems like Lubos has a large mote in his own eye? :-)

Lubos: "I think that it has become extremely unpleasant to be a part of
institutionalized science, and I am looking forward to be away from the focus of
these intellectual bottom-feeders who exist not only on Not Even Wrong and who
enjoy a silent approval by many of the leftist officials in the Academia."

Jack: "leftist"?

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