If a tree fell in Quantum Gravity...

[Jerry]

Trinitree extracted the following paper:
http://arxiv.org/ftp/arxiv/papers/1208/1208.3222.pdf
An Underlying Theory for Gravity
Yuan K. Ha

Ha's introduction is an overview of the expected properties of quantum gravity, pointing out that all of the observed properties are classical and because of the weakness of the force, most of the quantum properties will never be testable. This line also caught my eye:

[quote]All quantum field theories of gravity require the graviton as a mediating particle. The graviton corresponds to the weak field perturbation on a flat background spacetime.However, the graviton propagating in a flat spacetime contradicts the background independence of general relativity.[/q]

Isn't there a realization in this statement a fundamental contradiction between Relativity and Quantum concepts that cannot be resolved? A paradox that grounds one or both root theories as falsified? Sure, you can renormalize into comparable states, but renormalizing is nothing less than a statistical fudge factor that admits uncalculable nuances in our physical world.

Ha concludes:

We believe that gravity is in a similar situation. It would be impossible to quantize general relativity to achieve the smallest units of space and time in order to arrive at an underlying theory of gravity. A new structure with new degrees of freedom is needed. It is the statistical mechanics of spacetime.

[John Jaksich]

[QUOTE=Jerry;2056131]Trinitree extracted the following paper:
http://arxiv.org/ftp/arxiv/papers/1208/1208.3222.pdf
An Underlying Theory for Gravity
Yuan K. Ha

Ha's introduction is an overview of the expected properties of quantum gravity, pointing out that all of the observed properties are classical and because of the weakness of the fource, most of the quantum properties will never be testable. This line also caught my eye:

All quantum field theories of gravity require the graviton as a mediating particle. The graviton corresponds to the weak field perturbation on a flat background
spacetime.However, the graviton propagating in a flat spacetime contradicts the background independence of general relativity.[/q]

Isn't there a realization in this statement a fundamental contradiction between Relativity and Quantum concepts that cannot be resolved? A paradox that grounds one or both root theories as falsified? Sure, you can renormalize into comparable states, but renormalizing is nothing less than a statistical fudge factor that admits uncalculable nuances in our physical world.

Ha concludes:

Hello Jerry,

I read the paper with much interest-- it would seem (as you stated) that quantum gravity is more or less a statistical smoothing of a General Relativity? I would then surmise that any hypotheses for extra-dimensional theories of gravity (beyond four) would be in the realm of "black hole" cosmology?

Or, am in over my head?

[Jerry]

Hello Jerry,

I read the paper with much interest-- it would seem (as you stated) that quantum gravity is more or less a statistical smoothing of a General Relativity? I would then surmise that any hypotheses for extra-dimensional theories of gravity (beyond four) would be in the realm of "black hole" cosmology?

Or, am in over my head?

Ha mentions multidimensional approachroes as well, noting that the lack of measurable 'windows' within our own solar system contrains the available space for such paths to trivial or non-Copernican solutions.

I always run into philosophical problems with backing matter or energy into invisible places. Either it is there or it ain't.

[trinitree88]

[QUOTE=Jerry;2056131]Trinitree extracted the following paper:
http://arxiv.org/ftp/arxiv/papers/1208/1208.3222.pdf
An Underlying Theory for Gravity
Yuan K. Ha

Ha's introduction is an overview of the expected properties of quantum gravity, pointing out that all of the observed properties are classical and because of the weakness of the force, most of the quantum properties will never be testable. This line also caught my eye:

All quantum field theories of gravity require the graviton as a mediating particle. The graviton corresponds to the weak field perturbation on a flat background spacetime.However, the graviton propagating in a flat spacetime contradicts the background independence of general relativity.[/q]

Isn't there a realization in this statement a fundamental contradiction between Relativity and Quantum concepts that cannot be resolved? A paradox that grounds one or both root theories as falsified? Sure, you can renormalize into comparable states, but renormalizing is nothing less than a statistical fudge factor that admits uncalculable nuances in our physical world.

Ha concludes:

If a tree fell in quantum gravity, it's acceleration would occur stepwise as quanta of the gravitational field converted to teensy increments of kinetic energy....kind of like a motion picture projector....it only looks smooth because of our relatively large scale.

[borman]

Beware the insidious theoretical systematic

When Einstein worked on his general relativity theory with the evidence from Eotvos experiments, it appeared that the gravitational inertia was proportional to the Newton inertia. The constant of proportionality was refered to as k. Einstein did not over reach to give a specific value to k as any particular value could not be justified. There are two potential theoretical systematics that can enter.

One is an assumption that k=1 so that all of Newton inertia is also gravitational inertia. When this assumption is made with respect to the Dark Matter problem, then in the prevailing paradigm, if all the baryon Newton mass is all of its gravitational mass, then there must be some other unseen mass to account for the gravity, presumeably also assuming that k=1 for this other dark mass. Also from the assumption that k=1, and assuming there is no other Dark Matter forces Modified Gravity theories such as MOND or F(r). Less explored are the implications of k less than 1 or that the baryon proportion is less than one. Popular possible values would have k_baryons at .04, k_DM aroumd .28 and k_DE the remainder. Resolution of the Tate and Tajmar anomalies could be found by not assuming k_baryons =1 rather than finding fault with QM or General Relativity frame dragging respectively.

The other systematic is in making assumptions about the nature of the proportion of gravitational inertia. Is it correct to conclude that gravitational inertia is a physical fraction of Newton inertia? Answering this question has a bearing on the as yet unresolved "measurement problem" of QM. If the "real" world is the wierd QM world as our experiments suggest, why do we too often get a classical result at the large scale? (this was posited by Einstein to Max Born in a letter during his last year around '55}.
Some suggest holographic relationships which could include the Verlinde type. Another possibility other than the phenomenal route dominated by QM, is to consider that gravitational inertia is epiphenomenal rather than a phenomenal fraction of Newtion inertia. If Advanced LIGO and then LISA do not detect phenomenal gravity waves, we will need to explain how to keep the successful parts of GR without invalidating the theory due to absence of gravity waves. Do epiphenomena produce physical waves?

[Reality Check]

Beware the insidious theoretical systematic

When Einstein worked on his general relativity theory with the evidence from Eotvos experiments, it appeared that the gravitational inertia was proportional to the Newton inertia.
...

Beware the insidiously incorrect assertions
The Eotvos experiments showed that gravitational mass was equal to inertial mass within the experimental limits (1 in 100 million in 1909).
This has been improved on - see The Eöt-Wash Group Laboratory Tests of Gravitational and sub-Gravitational Physics (1 part in 10^13)

So in the rest of your post the upper value of k is 1.0000000000001.

[Jerry]

Beware the insidiously incorrect assertions
The Eotvos experiments showed that gravitational mass was equal to inertial mass within the experimental limits (1 in 100 million in 1909).
This has been improved on - see The Eöt-Wash Group Laboratory Tests of Gravitational and sub-Gravitational Physics (1 part in 10^13)

So in the rest of your post the upper value of k is 1.0000000000001.

Pretty good evidence that they are proportionally equal; I'm not sure the case has been established for the situation where both gravitational mass and inertial mass have the same constant of proportionality as a function of total mass. This is where I think the constraints are poorest and still need to be nailed down.

[trinitree88]

Beware the insidiously incorrect assertions
The Eotvos experiments showed that gravitational mass was equal to inertial mass within the experimental limits (1 in 100 million in 1909).
This has been improved on - see The Eöt-Wash Group Laboratory Tests of Gravitational and sub-Gravitational Physics (1 part in 10^13)

So in the rest of your post the upper value of k is 1.0000000000001.

Reality Check. Yep. But, it doesn't stop there. (Thought experiment within the known laws of physics.)
Suppose you have the supernatural ability to create a softball sized lump of degenerate matter at will. You are left floating in the Bootes void, far removed from any nearby stars in a spacesuit with ample oxygen supply by your trusted friends in their starship....along with your supernatural ability. At the count of ten, you materialize your softball lump in your hand. Should you now try to fire little thrusters on your spacesuit, you'll find that the ball's inertial mass has come into play...F=ma. Simultaneously, there appears a gravitational field, spreading outwards at c, (gravitational wave form) in inverse square law, and a pair of equal magnitude, opposite vector ,forces appears between you and the ball. (Newton's third). But that's not the limit in our universe. Our universe is pervaded by a relatively isotropic CMB radiation field (with the exception of the Axis of Evil @ ~ 7 sigma). Radiating from the softball, the spectrum redshifts slightly due to a local gravitational field well. And... our universe is pervaded also by a relatively isotropic neutrino sea. The mean free path for neutrinos in degenerate matter runs ~ 10 centimeters (David Arnett MIT Physics Colloquiem ). That's ~ softball size....so the sea neutrinos forward scatter off the nucleons, transferring energy and momenta...like a solar sail does for photons. This redshifts the neutrino sea spectrum emerging from the center of mass of the ball, travels outward at c from there, and is coincident with the gravitational wave from GR (assuming as the Particle Data Group Page does that the results from the neutrino flavor mixing experiments as yet do not conclusively rule out massless neutrinos traveling at c. That can only be ruled incontrovertible should neutrinos be seen to flavor switch in the absence of a matter path coincident with the beam in the experiment (has not happened yet...see Eta C's comments).
That means there are three masses. Gravitational. Newtonian Inertial. Neutrino Sea Interactive. The principle of equivalence is a trinity, and I'll bet my usual hot fudge sundae that when they sort out the gravitational wave algorithms at the LIGO upgrades, every wave seen will be coincidently seen in the most sensitive neutrino detectors (like SNO). pete

PDG:http://pdg.lbl.gov/

[Jerry]

The principle of equivalence is a trinity, and I'll bet my usual hot fudge sundae that when they sort out the gravitational wave algorithms at the LIGO upgrades, every wave seen will be coincidently seen in the most sensitive neutrino detectors (like SNO). pete

PDG:http://pdg.lbl.gov/

Sweet prediction. Must first indentify unambiguous gravitational wave. Given the current constraints, the unambiguity may be hard to come by.

[Reality Check]

That means there are three masses. Gravitational. Newtonian Inertial. Neutrino Sea Interactive.[/url]

I do not see that - all you have is neutrinos scattering , i.e. the inertial mass that appears in F=ma.

[trinitree88]

I do not see that - all you have is neutrinos scattering , i.e. the inertial mass that appears in F=ma.

Reality Check. It's not quite that simple. If you have a softball size degenerate mass at rest in your reference frame in an isotropic neutrino sea, you might decide to apply a force to it and accelerate it. Yep F=ma applies. It's new velocity, following your brief period of acceleration...F_new, can be plugged into SR to give it's relativistic mass increase using gamma. But that is accompanied by a simultaneous blue shift to the front hemisphere and redshift to the rear hemisphere of the neutrino sea (ignoring the CMB for isolation). That changes the interaction rates of those scatters since they're dependent on the energy per neutrino. The two effects are coincident, but not necessarily causal as we don't know the low energy density of the sea. To slow the mass down you reapply the force, delivering an opposite impulse, and the mass returns to rest in the frame, as the sea returns to isotropic.
Relativistic mass increase, length contraction, time dilation, and rotation known in SR,all are accompanied by a corresponding coincident increase of anisotropy of the ambient neutrino sea. Every experiment you have done or I have done or anybody anywhere has ever done is done in the ambient neutrino sea. We usually pay no attention to it, but it's there. In a room in the center of an asteroid, it's still there. In the center of a star it's still there.
In GR you can redshift a photon by sending it away from the center of mass. As it travels away the anisotropy of the sea decreases and it redshifts. Reverse the direction, reverse the effect. A binary pulsar sends out gravitational waves in GR (LIGO searches)...but it sends out something else,too....as the two masses swing around their center of mass, they move towards ans away from your line of sight......redshifting and blueshifting the sea they interact with and the gravitational wave is accompanied by a neutrino sea wave. Similar effects occur in the precession of the perihelion of Mercury.
Can it be shown that the effects in the sea are non-causal? Yep. Take a Mossbauer detector (used in the Rebka/Pound Harvard Towers experiment) and point it at a reactor (spallation source) coming back on line after a refueling, with the detector not quite out of resonance as it does. If it doesn't blink....I do. Been waiting for that test since April of 1982. All Mossbauer detectors should have blinked during SN1987a. Said that Williams College in 93. Got a standing ovation for that talk in front of ~400 PhD's at the jointly held AAPT/APS conference..(.I was quite surprised). That's the highest level in the world ...on a par with lots of the bright people in this forum. They essentially agreed. So, I'll stick to my guns,here. pete

a first rate theory predicts

[borman]

Beware the insidiously incorrect assertions
The Eotvos experiments showed that gravitational mass was equal to inertial mass within the experimental limits (1 in 100 million in 1909).
This has been improved on - see The Eöt-Wash Group Laboratory Tests of Gravitational and sub-Gravitational Physics (1 part in 10^13)

So in the rest of your post the upper value of k is 1.0000000000001.

The Eotvos and follow up experiments do not measure the value of k. They measure any variation of the value of k between different quantities that have the same inertial mass. What is being measured to parts per 20 trillion is that k is a constant. The experiments measure k_baryon Sample A/k_baryon Sample B=1 to parts per trillion. This is valid for any arbitrary value of k except 0 which is a continuum of values. That a particular solution is k=1 was part of the Einstein idea of the Principle of Equivalence from 1907. He considered experiments to test the idea and was informed and pleasantly surprised to find Eotvos had done experiments 20 years earlier. While the experimental results do not refute that k could be equal to 1, they do not prove it either. Rather what is supported is that k is a constant of the properties of any particular mass which is sufficient to treat the problem of gravity as geometry of spacetime. That k must also equal 1 is unnecessary.

The mass anomalies observed in low temperature experiments (Tate, NCRI, Podkletnov, Tajmar) do not necessarily also mean that the value of k is different for these. They would have to be tested by an as yet to be performed Eotvos experiment to make observations. For example with the Tate Anomaly, Cooper pairs of electrons have greater observed mass than two unbound electrons, contrary to theoretical predictions by 7 orders of magnitude. So one sample would contain some of the more massive Cooper pairs and the other would contain enough extra electrons to balance the first sample as regards Newtonian inertia. Then perform the Eotvos test to see if they have the same fraction of k when compared to each other.

Some possibly useful references:

Universality of Free Fall
and General Relativity

http://www.kfki.hu/~tudtor/eotvos1/UFFEotvos4.pdf

Physical and Epistemological Foundations of Einstein's General Theory of Relativity
http://aero.stanford.edu/GTR.html

Origins of Mass_
Frank Wilczek
http://arxiv.org/abs/1206.7114