Thomas R. Love's discussion of Carlo Rovelli's Quantum Gravity book
I reviewed Dr Thomas Love's paper, Towards an Einsteinian Quantum Theory, in a previous post. He has several other interesting papers as well as his many mainstream publications. One part I did not comment on was a major argument that the best approach to quantum gravity is to replace the Standard Model groups SU(3) x SU(2) x U(1) with the complex spacetime U(3,2)/U(3,1) x U(1), and to interpret the latter as excited states of anti-de Sitter spacetime. I investigated anti-de Sitter spacetime about a decade ago and it just didin't have any empirical validity. While I'm convinced that the Standard Model has validity in some sense, and I have sympathy with electroweak theory SU(2) x U(1), there is evidence that the strong gluon mediated color charge force of SU(3) is incomplete. The exact reason why to make the theory work there are 8 rather than 3 x 3 = 9 gluons to mediate the color force, would appear to indicate that the maths has been pushed on to the physics; it works at checkable energies and distances, but it is incomplete as shown for example by the fact that it does not unify naturally with electroweak forces at extremely high energies.
I've just read Thomas Love's paper Elementary Particles as Oscillations in Anti-de Sitter Space-Time. The major portion of it, the first 80 pages, deals with expansions and applications to U(3,2)/U(3,1) x U(1) of the spinor differential operator representation of U(3,2), which I'm really totally unqualified to comment on. I do not have much knowledge of this specialist area. The only comment I can make in superficially looking at that material, is that it is a large amount of formal and abstract mathematics.
Moving on to page 82, section 28: The Meaning of Quantum Gravity, Love helpfully reviews some of the claims made by Carlo Rovelli in his 2004 book Quantum Gravity (Cambridge University Press). As pointed out earlier on this blog, Rovelli is critical of 'string theory':
'The history of science is full of beautiful ideas that turned out to be wrong. The awe for the math should not blind us. In spite of the tremendous mental power of the people working in it, in spite of the string revolutions and the excitement and the hype, years go by and the theory isn’t delivering physics. All the key problems remain wide open. The connection with reality becomes more and more remote. All physical predictions derived from the theory have been contradicted by the experiments. I don’t think that the old claim that string theory is such a successful quantum theory of gravity holds anymore. Today, if too many theoreticians do strings, there is the very concrete risk that all this tremendous mental power, the intelligence of a generation, is wasted following a beautiful but empty fantasy. There are alternatives, and these must be taken seriously.' - Carlo Rovelli, arXiv:hep-th/0310077, p20.
Love rightly points out some problems in Rovelli's approach. Rovelli states on page 4 of his book Quantum Gravity that:
'We have learned from general relativity that spacetime is dynamical and we have learned from quantum mechanics that any dynamical entity is made up of quanta and can be in probabilistic superposition states.'
Love showed in the earlier paper that 'probabilistic superposition states' are a fallacy due to the switch over that you can make between the time-dependent and time-independent forms of Schroedinger's equation at the moment of taking a measurement: the wavefunction collapse is a manifestation of the mathematical discontinuity which is a human calculating problem in the maths. So wavefunction collapse is not a physical fact: it is not inherent in physical events except in the straightward causal sense that you physically (not magically) disturb something by poking it with a stick or a particle when you take a measurement.
Love also disagrees with the argument that general relativity demands a dynamical spacetime. I agree with Love: matter and radiation are dynamical, and spacetime is used to measure such dynamics. Perhaps Rovelli meant that spacetime fabric appears to be dynamical; if so he should have said so. In fact you later find that Rovelli does say so, on page 9 of the book: 'General relativity is the discovery that spacetime and the gravitational field are the same entity.' (This is as false as saying that energy and mass are 'the same' because of E=mc2 in special relativity.) It is true that general relativity shows that the amount of deflection of light (or other radiation travelling along geodesics) is directly proportional to the gravitational field strength, but this doesn't indicate they are the 'same entity'. According to the Standard Model, there appear to be several exchange radiation types for different force fields (strong nuclear, weak nuclear, electromagnetic), and these fields related to spacetime but are not the same entity as it. Rovelli might as well claim 'a ruler is the same entity as distance' or 'a clock is the same entity as time', just because there is a direct relationship in each case. This is simply not scientific or careful.
Rovelli does immediately improve the situation slightly by adding: 'What we call "spacetime" is itself a physical object, in many respects similar to the electromagnetic field. We can say that general relativity is the discovery that there is no spacetime at all. What Newton called "space", and Minkowski called "spacetime", is unmasked: it is nothing but a dynamical object - the gravitational field - in a regime in in which we neglect its dynamics. ... the Universe is not made up of fields on spacetime; it is made up of fields on fields.'
I agree with Rovelli in the sense that gravity can be modelled dynamically as due to exchange radiation in a Yang-Mills type quantum field theory, but I think he should distinguish the dynamical field from spacetime, just as you should distinguish a ruler/clock from distance/time.
What gets me very angry is censorship effect such illucid/slack and simply careless popular terminology has on a simple fact I grasped a decade ago: geometric volume is distinct from the content of that volume, so receding matter vacates observable volume around us by recession. Since there is no mechanism for the spacetime fabric/Dirac sea/quantum foam vacuum to do anything except fill the volume where there is no matter [Dirac's theory; it predicted antimatter], the observable recession of real mass around us in spacetime automatically results in an equal and opposite inward pressure from the Dirac sea pressing inward to fill in the volume. (This directly led to the original calculation of gravity via the October 1996 Electronics World magazine, due to censorship by Campbell and Ziemelis at Nature, which has since been developed further, and supplemented with a Yang-Mills exchange radiation heuristic calculations that give the same correct prediction of gravity to within 1.7%.)
Love also takes issue with Rovelli's statement on page 5 of his book:
'The fact is that we do have plenty of information about quantum gravity, because we have quantum mechanics and we have general relativity. Consistency with quantum mechanics and general relativity is an extremely strick constraint.'
Love points out that this is misleading because the usual formulation of quantum mechanics is inconsistent with the usual formulation of general relativity. Love's argument is that both the usual structure of quantum mechanics and that of general relativity must be modified slightly.
Rovelli is concerned in his book with Loop Quantum Gravity. The main point about Loop Quantum Gravity is that it is a mathematical unification between Feynman's quantum field theory 'path integrals' and background independent general relativity, general relativity without a specific metric.
In this sense Loop Quantum Gravity, which sums Penrose spin network interaction graphs for all the interactions to arrive at the Feynman path integral, is going to be true.
All you have to do is to supply Loop Quantum Gravity (which is purely a mathematical calculating equivalence between general relativity and quantum field theory) with some dynamics for gravity and the PHYSICAL contraction which creates a dynamical compression of matter by gravity (contraction is usually falsely attributed to a metaphysical special relativity metric), and you get quantum gravity unified with general relativity. Problem sorted!
Of course it is not so easy: although by putting my censored dynamics into the Loop Quantum Gravity of Penrose, Rovelli, Smolin, etc., unifies quantum gravity with general relativity and allows predictions to be made of all kind of things which were later experimentally confirmed, there are still issues with electroweak symmetry breaking and also Standard Model force unification in the absence of supersymmetry.
Love states on page 83 of his paper: 'Like the GUTS program which ignored gravitation and could not possibly lead to a totally unified theory in which the particles arise from the gravitational field, Rovelli's LQG program cannot be made consistent with a unified theory of all interactions.'
This is literally true, but there is no problem with LQG just describing gravitational effects (gravity and contraction consequences, spacetime fabric) if the Standard Model is retained for the other forces. It all depends on whether you are somehow certain that gravity is a quantum field theory somewhat like the Standard Model quantum field theory, or whether you just want a description that works and is compatible with the Standard Model.
On page 87, Love explains the structure of matter clearly: 'what we call elementary particles are actually patterns of energy flows in what we normally call the field of the particle.' Love then quotes Hans C. Ohanian ('What is Spin?', Am. J. Phys. 54, 1986, pp. 500-505):
'[Belinfante in 1937] established that the spin of an electron could be regarded as due to a circulating flow of energy, or a momentum density, in the electron wave field. He established that this picture of the spin is valid not only for electrons, but also for photons, vector bosons, and gravitons - in all cases the spin angular momentum is due to a circulating energy flow in the fields. Thus contrary to the common prejudice, the spin of the electron has a close classical analog: It is an angular momentum of exactly the same kind as carried by the fields of a circularly polarized electromagnetic wave.'
I haven't read that article, but presumably that it means is that the electric field vector rotates a half turn per revolution (this rotation is described as circular polarization) in going around in a circle. This makes the electron like a Mobius strip (a strip of paper glued into a loop containing half a twist, so that both sides are joined as one and if you draw a continuous line around it, the line will cover both sides and have twice the circumference of the loop), in that it must be rotated 720 degrees to get back to starting point (one complete transformation); electrons have spin 1/2, which implies this concept (spin 1 is normal spin).
This is exciting as I've come to the same conclusion from experimental electromagnetism evidence. This is concerned with a vacuum dielectric capacitor storing light speed logic pulses of v volts and x metres length and discharging them into sampling oscilloscopes as pulses of v/2 volts and 2x metres width, which implies that trapped electric charge such as static electrons are dynamic with some kind of light speed energy oscillation or real spin; because the trapped energy goes all directions, when you discharge a capacitor plate at one end, half the energy is already going towards that point in a pulse of v/2 volts and x metres long, while the other half is going the opposite way in a pulse of v/2 volts again x metres long; it reflects from last bound electrons at the other end of the plate and exits consecutively, giving a total combined output pulse of v/2 volts and x + x = 2x metres duration!
The magnetic field curls from each opposite-direction superimposed energy flow in a stable, 'static' charged wire (or anything else) cancel, but the electric field vectors from each component add up. Transverse electromagnetic, TEM, wave of electricity as photons: Yang-Mills quantum field theory, unitary group U(1) in the Standard Model of particle physics, established circa 1974. This describes all electromagnetic interactions as the result of exchange photons. TEM wave electron model was first established in 1937 and is now verified by Love's analysis of the cause of the superposition/entanglement of states mechanism (it is just due to a mathematical problem, the discontinuity between the time-dependent and time-independent forms of the electron wave equation when a measurement is made).
Update: someone brave has anonymously stepped in to defend the QCD gluon exchange model from further development (see comments in this post), claiming that any increase in dynamical representation of reality is an 'insult' to science. My response: Take a proton; two upquarks and a downquark. The two otherwise identical upquarks according to QCD have different color charges. (I'm not interested in color charge being determined at the moment of taking a measurement by collapse of the wave function, since in a sense the color charge is continuously in evidence because protons don't explode under electrostatic repulsion, because the color force keeps keeps them together.) SUSY was invented to make the strength of the QCD interaction the same as electroweak interactions at extremely high energies.However, approaching the problem from another (physics-based not speculation based) angle, you can see the true mechanism for unification:
Electric charges are shielded by the polarized vacuum field they create at short distances. If you hypothetically put three electron charges close together so that they all share the same vacuum polarization cloud, the polarization in that cloud will be three times stronger. Hence, the shielding factor for electric charge will be three times greater. So the electric charge you would theoretically expect to get from each of the three electron-sized charges confined in close proximity is equal to:
This is the actual size of the downquark charge observable from a distance! In developing this model we have unification: the conservation of energy tells us that the shielded energy of Yang-Mills exchange gauge bosons from the electromagnetic interaction gets used in some other way. Doh... the strong nuclear force and the weak nuclear force. (This is the fact based path to the final theory: nothing new, just some logical structure imposed on what is already known, some interconnections.) A proton has a charge +1e instead of say +3e, because (1)opposite charges "cancel out" and (2) there is shielding by the polarized vacuum which converts some electromagnetic energy into short-ranged nuclear forces.
A proton has some residual electric charge because the attenuated electromagnetic field energy is used only for QCD binding energy. A neutron has no residual electric charge because, in addition to the QCD binding force, it has also considerable weak force binding energy (free neutrons will decay into protons by beta radioactivity). To get force unification qualitatively as well as merely quantitatively (SUSY is only quantitative), means accounting for the differences in charges between leptons and quarks, which in turn will mean a better understanding of gluons.
Gluons are a bit like the Higgs bosons: you can argue that Higgs bosons are vital because they give rise to all mass, which is an observed fact. But that is pseudoscience: like arguing that Ptolemy's epicycles 'must' be real because we see the the sun and stars appear to orbit the earth, that phlogiston is proved real because 'fires burn', and that caloric is proved real because temperature is measurable. (These examples led Sir Karl Popper to formulate the absurd and false suggestion that being falsifiable means being scientific: which is a lie because it includes epicycles, phlogiston, and caloric before those pieces of speculative trash could be disproved!!!!! So just because something is falsifiable doesn't means it is scientific! What you want is a theory which is grounded in hard logic and experimental observations, such as Archimedes proof of the law of buoyancy. That is definitely science precisely because it is not open to potential falsification! Archimedes proved buoyancy laws directly using observable facts and logic. Popper simply ignores Archimedes' On Floating Bodies.)
I'm not arguing that QCD is completely wrong or that gluons don't exist, because clearly the theory works mathematically (although it leads the mainstream into extravagant SUSY speculation).
Science is concerned with clarifying and analysing facts, and is not concerned with religious worship of QCD. I just want to know the dynamics of what is really occurring. If you are a mathematician - as I suspect - consider the fact that there is more than one way to prove certain theorems, and some ways are clearer and more interesting than other ways. I'd like to see a causal interpretation of the standard model, BECAUSE THAT WILL LEAD TO EXPLANATIONS FOR THE STANDARD MODEL PARAMETERS:
Guess a mechanical-type analogy (simple polarization, exchange of radiation, etc), then see if you can get it represent the abstract theory. This will work because the abstract theory has been guessed as a model for nature in the first place. All you are doing is finding the underlying dynamics. It could be that the standard model is an exact representation (in abstract terms) of reality, but there are still issues over the exact chiral symmetry mechanism etc.
Copies of comments to Cosmic Variance physics blog, in case deleted:
Science on Jun 21st, 2006 at 12:06 pm
Neither the equations of quantum mechanics nor Alain Aspects experiments disprove causality proper or prove Copenhagen philosophy/politics/religion. So please don’t throw that around here.
Dr Thomas Love has proved that the entanglement philosophy is just a statement of the mathematical discontinuity between the time-dependent and time-independent Schroedinger wave equations when a measurement is taken. There’s no evidence for metaphysical wave function collapse in either the authority of Niels Bohr, the Solvay Congress of 1927, or Alain Aspect’s determination that the polarization of photons emitted in opposite directions by an electron correlate when measured metres apart.
Accept that Copenhagen quantum mechanics is speculative. Don’t build it up as a pet religion. The uncertainty principle in the Dirac sea has a perfectly causal explanation: on small distance scales, particles get randomly accelerated/decelerated/deflected by the virtual particles of the spacetime vacuum. This is like Brownian motion. On large scales, the interactions cancel out. If so, then photon polarizations correlate not because of metaphysical “wavefunction entanglement” but because the uncertainty principle doesn’t apply to measurements on light speed bosons, and only to massive fermions which are still there after you actually detect them.
Science on Jun 21st, 2006 at 4:50 pm
Everyone is trapped into supporting string theory if they want to get published, or even on arxiv. If you get suppressed for having an “alternative to currently accepted [string] theory” (Stanley Brown, PRL editor, in email to me), that’s equivalent to be trapped into supporting string theory.
When you point out that there isn’t a proper theory there at all unlike your work, they give you an abusive rant about their personal problems in life or whatever, and when you point out they are just bitter, you just get get them saying the same thing back to you. They just act like kids and hurl abuse. You can’t answer back, or they say you are being censored for being rude.
Science on Jun 22nd, 2006 at 4:44 am
Witten’s hype seemed to stop around 1998, though. By coincidence, this is also the year that the CC was found to be positive, something that EW described as the most disturbing fact he had ever learned.- Thomas Larsson comment #116
Please don’t spread this CC propaganda. The evidence in the data is that the supernovae weren’t slowing down, and the data don’t prove that the reason is CC/dark energy offsetting gravitational deceleration. The effect was predicted in a paper published in Electronics World October 1996 which was censored out of more appropriate physics journals for disagreeing with mainstream speculation. Gravity is generated by surrounding expansion which predicts the strength of gravity correctly and also predicts that the distant expansion is not being slowed down. Just goes to prove that Kuhn was wrong. Make correct predictions, and you get more censorship and downright abuse when they’re confirmed by observations two years later!
That’s because the mainstream (string theory) derives its power not from empirically defensible physics, but from censorship on non-scientific reasons like mere disagreement with mainstream speculation.
Science on Jun 22nd, 2006 at 4:58 am
"...Dirac sea, you seem to think that the uncertainty arises due to imperfect knowledge of the system (Brownian motion is a classical phenomenon). This is called a hidden variable theory, and was explicitly ruled out by Bell’s formulation of his famous inequaliies." -PK #110
No, the Bell inequality deals with Bohmian hidden variables which are wrong. The quantum vacuum effects in say the Casimir force and the polarization of the vacuum which shields charge cores are directly observable. In 1997 Levine and others collided electrons at 90 GeV and noted a 7% increase in electron charge, due to penetration of part of the polarized shield of vacuum charges around the electron core. It is empirically confirmed. Bohm build up an elaborate class of theories with infinite potentials and "pilot waves" which were ruled out by Bell's inequality. If you want to promote entanglement, may I suggest you find a UFO blog to do it on?
Science on Jun 22nd, 2006 at 4:57 pm
PK on Jun 22nd, 2006 at 8:39 am
Science: Bell showed that in local hidden variable theories we can derive Bell inequalities (which are violated in experiment)....
This is a posting about string theory not Bell’s theory. If you want to know, Yang-Mills exchange radiation is the mechanism. You can discuss on my blog if you want. Must not go off topic of strings here.
The neutron is dominated by strong nuclear force effects. The physics is dominated by the fact that you have several charges very close together in a neutron or proton. Each charge, even electrons, have a polarised shell of virtual charge around them, created in the strong field at short distances. I have gone into the nuclear forces in detail, as nuclear physics was originally my major interest. The short range forces are effects in the polarized shells around charged particles. If two particles get close enough that their polarized shells of virtual charges overlap, strong forces result. Once you are inside the polarized shell, the force from the polarized shell itself falls off as you approach more closely to the real cores, because the thickness of polarized shell between you are the core deceases as you approach the core. Hence the strong nuclear force actually falls at very close-in distances as you approach the core, while the electromagnetic force gets less and less shielded by polarization and ecomes stronger. The equilibrium when these force variations with distance offset one another in a nucleon causes the "asymptotic freedom" of quarks within a nucleon.
Also, suppose for sake of argument you put 3 electrons close enough together that they were separated by distances like the distances between quarks in a nucleon (neutron or proton). In that case, a very interesting piece of physics emerges very simply: all 3 particles SHARE THE SAME polarized shield, which because it is proportional in strength to the electric field strength, is then exactly 3 times stronger than in the case of a single electron, because it is contributed to by the 3 electrons instead of by just 1. So the polarization electric charge shielding factor will be increased by a factor of 3, and each electron will have an apparent charge (seen from beyond the polarised charge shell) of 1/3 of the electron's charge. The downquark has exactly this electric charge, -e/3!Hence downquarks can be shown to be like electrons locked in pairs or triads of quarks, and the special forces and properties result from this entrapment effect on the shared polarization of the vacuum which shields the core charge. Consider energy conservation! What happens to the electric charge energy when the electric charge is shielded by a factor of 3? Simple: nuclear force field effects! This is a quantitative prediction which affects the unification of forces in the Standard Model, replacing string theory's supersymmetry (SUSY) to explain high-energy unification effects, and is better than string as it makes checkable predictions even at low energy.
This nuclear mechanism appears to be on the right lines. Obviously the upquark, with charge +2/3, is more challenging than simply putting 3 positrons in close together so that they share a vacuum polarization which is 3 times stronger, shielding the individual positron charge by a factor of 3 to +e/3. The upquark charge is +2e/3 not +e/3. The reason is that when you put different charges together, the effects on the polarized vacuum become complex.
Suppose you have just an electron and a positron close together, like a pair of quarks in a meson. In that case the net electric field is zero at long distances. What happens to the energy of the electric field in space when you bring a positive charge beside a negative charge? The late Dr Arnold Lynch, who during the war helped build the Colossus computer that broke the Nazi codes, worked on microwave beam interference problems for BT in the 1980s. He wrote to me that experimentally the superimposed field energy is still there, even when you can't detect any fields due to perfect interference (cancellation). The fields become hidden, but the energy is still there in space, as can be shown by their immediate reappearance if the cancellation is stopped by ending one of the two interfering beams.So in a neutron, with some electromagnetic field energy at very long distances as a magnetic field (since the neutron has a magnetic dipole moment) the physics is intricate. To calculate the amount of energy available to create and polarize virtual charge (which in turn attenuates the real core charge as seen from a large distance), you need in either a neutron or a proton (or other particles) to take account of the energy residing in the magnetic field of that particle. Neutrons and protons both have magnetic dipole moments.
The fact that nuclear particles containing quarks have magnetic moments makes the physics of where shielded energy goes, a very subtle challenge to analyse. Part of the magnetic moment is from the virtual charges being polarized and aligned in the vacuum. The official mainstream theory of strong nuclear interactions, QCD or SU(3), cannot predict very much very accurately because it is an abstract analytical theory which is not easily solved by computer calculation. The whole of nuclear physics needs to be physically represented as causal models which are less abstract and more pictorial, before progress is made. The main successes of the standard model in terms of numerical predictions are for weak nuclear forces where there are only 3 gauge boson types, not strong forces with 8 gauge bosons.