Does LQG Do Nothing Cool Even If It Is Right?

[Paulibus]

Interesting remark:

But 'what if' it's a masquerade of the same thing like what happened to the early fields

My grip on physics history is shaky! Which early fields? Are you perhaps thinking of old vortex-theory days?

 

[marcus]

Michael Faraday? around 1820? I think he was the one who got the idea of "fields" (maybe like a field of grain or high grass, when the wind blows and the blades lay over in shifting patches pointing this way or that?). He had the idea of "field lines", looking for example like the lines of iron filings on a piece of paper with a magnet underneath.
He thought of fields with their field lines being the fundamental reality. (He did not accept the idea of "aether". The world was full of field lines, certain forces were in effect "made of" field lines.)

There were at least two kinds of fields. The electrostatic field lines that arise between pos and neg charges, and the magnetic field lines that arise from and connect the N and S poles of a magnet. These were different fields (for Faraday). They were produced differently, and affected different things, and behaved in different ways.

I think it was around 1870-1880 that Maxwell discovered that the E and the M fields of Faraday were actually different parts of the same field. There was really just one field, the EM field, and a change in one part produced changes in the other.

A change in the magnetic field seemed to produce electrostatic force in that it would push charge along a wire and make current flow. A conductive wire moving relative to a magnetic field, moving through a field, experienced change and a current would be induced in it. Also a current flowing in a wire would, itself, set up magnetic field lines. You could concentrate these magnetic field lines by winding the wire into a coil. The two types of force arise from the same thing, and so their influence on each other was eventually explained.

So maybe geometry and matter arise from the same thing and this could explain THEIR influence on each other

 

[Paulibus]

Thanks, Marcus. Yes, Faraday invented the field concept, which gains huge credibility when one looks at patterns of iron filings near a magnet and leads on later to Maxwell's quantitative description of interactions between charges in terms of dynamic E and B (or is it H?) fields. Fields are great mathematically tractable descriptive tools. But these fields are not the same thing as the charges (static or moving) that generate them. Similarly with the gravitational field; which is not the same thing as the mass/energy that is the field's source. And in linearly elastic media, where tensor fields describe both stresses and the strains that cause them, stresses are not the same animals as strains.So, being pernickety, I don't see that there's any masquerading in the description we give of gravitational interactions between lumps of mass/energy. In these cases cause and effect differ. I think?

 

[julcab12]

Interesting remark: My grip on physics history is shaky! Which early fields? ?

... It was Newton -- Newtonian spacetime. It is pictured as metrical structure. Then came Special relativity, loosing the strict distinction between "space" and the "time". The usual 3d space (Newton) became 4d manifold with a flat lorentzian metric. Dynamic objects moving over spacetime includes a field as well. Then, GR came with a tweak on the Newtonian spacetime into gravitational field which is represented by a field on spacetime. IN terms, the Newton's background spacetime is the same as gravitational field. We learned that GR's spacetime is a dynamical field, obeying dynamical equations. The gravitational wave is similar(almost) to an electromagnetic wave. Every dynamic object has a quantum property to it, which can be captured by formulation of dynamical theory within QM. Spacetime itself exhibit quantum properties -- metrical. We can consider that Spacetime / gravitational field, is a dynamic entity with Quantum properties.

-- I'm only saying this on a full relational view; nothing more but a construction of space(localization)/time and motion that is modeled fragmentary but deeply rooted like it is one of the same fundamentally. I'm just a reader and please do correct me if i went a bit far.

 

[Jimster41]

So maybe geometry and matter arise from the same thing and this could explain THEIR influence on each other

Whether or not space time itself is ultimately continuous or discrete or made of cheese-cats is unknowable (as Marcus says, "It's all just experience"). Schroedinger's amazing and spare "What is Life" is the best debunking of such philosophical conundrums I have ever read. As I recall it says basically the same thing. The question then is whether or not we are decomposing our (shared) experience of whatever it is as a set of continuum fields acting on particles, an approach that has hit some pretty major obstacles, or something else. What I like most about Energetic Causal Sets, or Causal Spin Foams, at least as I understand them, is that they free us from the notion of a continuum gravitational field (one major bugger obstacle). Instead they provide a way of thinking of space-time curvature and all it implies, gravity, mass, acceleration, as potentially being the emergent result of an evolutionary game called "space-time geometry". The stochastic math of Evolutionary Dynamics would say emergent structure is inevitable when states iterate under rules on a gradient, or "fitness landscape". And if all those key bugger tough pieces can be successfully imagined in this way then why not all the known particles and forces. At one level, this picture of fundamental physics as a smooth extension, or "root" of the more familiar kinds of evolution kind of seems disappointingly obvious. But if you do buy it for a second, the really intriguing question is, in what fitness landscape is all the hardware of our experience evolving? I think Verlinde might suggest it skulks around in the brilliant guise of "The Second Law of Thermodynamics". To me this is a profoundly coherent and complete picture... And it points to other puzzle pieces, the Hubble constant, "dark matter and energy", quantum non-locality, generally-ubiquitous-periodicity (or discrete scale invariance) and extreme space-time forms like Black Holes. These bother me a lot, because they almost seem to fit, in such a schema.

 

[Jimster41]

Dark Matter and Energy: If the driver of curvature is not Mass or Energy, but rather they are emergent types of curvature, then options for understanding other types of curvature seem to open up

The Hubble constant: The apparent acceleration of all objects away from each other, also a case of space-time curvature, does not need to be accounted for strictly from initial conditions. Rather it could be THE driving condition, manifest, the changing phase space of our space-time which drives the second law, causing all other space-time structure to emerge.

Quantum non-locality and Discrete Scale Invariance: tricky. Evolutionary dynamics allows for rich structure to emerge from simple rules under iteration, even periodic structure, especially periodic structure. However, if particles are emergent space time phenomenon, and the game of Space-time curvature evolution has non-local components, which by all accounts to date, it appears to - meaning the photon that went through the right slit at 2pm apparently interfered with the photon that was seen passing through the left slit, at 3pm, then there could (at one level there simply are) patterns of structure in our space time evolution that are caused by non-local, and/or a-temporal accounting. The implication, to me is that the causal wave that forms our space time is not wholly... All that is fundamental. This, points back to all of these other pieces - shedding new light on what they could mean.

Extreme space-time forms, black-holes, pulsars. These could be perceived as simple run-away emergence of space-time curvature structure, or even more outlandish, as structures of a-temporal resonance, feedback phenomenon, ringing in the true universe which must contain our parochial little space-time. Dark Matter and Energy could just be their extended limbs - or ripples or harmonics. The Big Bang could even be their lensed reflection on the surface of our space-time's container. Or the shape of the dent everything that will ever happen here, has made in that surface.

I'm working through Penrose' "Cycles of Time" I think his notion of conformal geometric symmetry (with inverted energy density) at the beginning and end of our space time plays very nicely with my fantasy of ECS. I do think he bangs his head looking for the continuum g field. Though it seems prescient that he speculates on a particle (even non interacting) having non constant rest mass.

Also I understand they are testing the last loophole in Bell's Inequality - the so called "free will loophole" I for one am perfectly happy to call it a day with 2 out of three, because if the hidden variables turn out to be "universal predetermination" I think it only makes the already crazy point the two slit seems to make anyway. Time is certainly a bizarre illusion we can't escape, and causality, well that's likely kind of the same deal.

 

[Jimster41]

It may seem off putting to imagine the "laws of physics" evolving. I don't think I'm speculating to that end, I'm suggesting (interpreting the Pros) that the fundamental objects of our experience all particle/energies, not just all the compound objects like plants and animals and stars could be (best) described in the language of Evolution, where some relatively simple system is iterating under a set of rules, and a fitness landscape and all other structure is emergent. For this to be, there has to be some at least relatively stable, though not necessarily fixed rule set, like the rules of ECS, and some similarly stable fitness landscape.

By proposing that space time curvature (aka gravitation force and the measure of Mass) is "an emergent result of entropy" Verlinde has bridged what seems to me to be an obvious gap, in hindsight. The evolution of space-time curvature is given it's fitness metric by changing (increasing) phase space which manifests as the second law and the "entropy tensor". From this evolutionary system, iteration emerges specific curvature forms. It seems of no small importance that this can provide a fundamental root cause for evolution as a whole, or rather is consistent with what we already know - that macroscopic natural evolutionary processes are driven by the 2nd Law. Life is an entropy minimization machine.

So how might the Hubble expansion of phase space (available states) induce curvature. I'm just trying to think about this... If I start with two coins, one bucket. Since there is only one bucket both coins have to be in that bucket. There is no freedom of configuration and no question about configuration equilibrium under repeated questions about configuration. If you add a bucket, you have introduced a "configuration tensor", an entropic gradient or curvature. Repeated random choices of configuration require even distribution to emerge from a state of uneven distribution, probability fills probability space evenly (Louiville's theorem).

So why doesn't the system go to equilibrium phase space distribution immediately? Why is the curvature so lumpy? Stochastic processes starting from nearly identical initial states, can have highly divergent end states. So you can imagine the small difference of the two coin two bucket case ending up in some intermediate-state with complex, lumpy, distribution structure after a whole bunch of buckets have been added, and the configuration question has been asked some number of times. However, I think I can imagine how the divergence to lumpiness might be driven by some additional effective cost term that resists the equilibrium distribution tendency. Maybe it's only the relationship between the rate at which re-configuration steps are taken, and the rate of buckets being added. My hunch is that something as simple as that ratio, given the surprising math of iteration and evolution, could explain locally stable curvature attractors, or "curvature sinks" - i.e. everything from massive particles to black holes.

So what about all the rest of the standard model, that is not gravity? Well to my thinking E=m*c^2 and all of that various mass and energy, since it exists in space-time, could be (should be) explainable as emergent structure of space-time curvature evolution. The zoo of fundamental particles would just be a case of discrete scale in-variance (repeated, and re-normalized patterns of emergence) in interacting or "co-emerging" structures, in other words they are just creature-like mixes of curvature attractors of different evolutionary histories.

Sorry about all this, I'm done.