Subject: Re: Woodward's objection - frame artifacts Unruh effect ---> virtual computed reality?
On Feb 10, 2011, at 12:11 AM, Paul Zielinski wrote:
On Wed, Feb 9, 2011 at 9:45 PM, JACK SARFATTI <
On Feb 9, 2011, at 7:01 PM, Paul Zielinski wrote:
Depending on how this result -- if it holds up -- is rationalized theoretically.
J: How does that help? Think of this more like a murder investigation. We have a very important clue - a natural derivation of
hc/RH^2LP^2
as a horizon Unruh effect, but the horizon must be in our future in accord with Yakir Aharonov's QM for example.
Z: Well the thing is, this is a Rindler horizon, not a black hole horizon. A Rindler horizon is a frame artifact.
J: (BTW from EEP near any horizon there is an equivalent small Rindler wedge - indeed one form of entropy emergent gravity uses that trick.)
Exactly, and so is our cosmological horizon! So what's your point?
g00 = 1 - /\r^2
(in static LNIF (fixed r) representation using the "gravity shift" not the FLRW "cosmological shift" for co-moving LIF representation where g00 = 1)
is observer-dependent we here now at a(t) = 1 in Tamara's picture are at r = 0 - at z = 0.
Z: Agreed that the issues I'm trying to raise here are built into the entire Davies-Fuller-Unruh model in which the level of excitation of the quantum fields is inherently observer frame dependent. According Crispino et al. these same questions have been raised by many physicists. In fact I gather there has been quite a lot of skepticism regarding the whole idea of Unruh radiation in the literature. Crispino et al. argue that detectors are not important, since the physical results of applying field quantization to a classical wave equation, even in a flat spacetime, are *inherently* frame dependent. the number of quanta automatically varies according to which coordinate frame is used to describe the quantized field. For me this raises serious questions about the physical meaning of field quantization, or about the mathematical formulation of the theory of quantized fields.
J: Operationally, only relationships between COINCIDENT local frames are physically meaningful and they are ultimately small idealized detectors. All the gauge transformations are between such coincident detectors.
tetrad transformations are LIF <---> LNIF
Lorentz group transformations are LIF <---> LIF'
GCTs aka T4(x) are LNIF <---> LNIF'
That's all the real spacetime physics (purely formal coordinate relabelings are always divided out of the physical measurements).
Then there are the internal symmetries U1, SU2, SU3 - that ultimately must be formulated in terms of detectors also, though I don't think anyone really worked it out since Bohr and Rosenfeld and Wigner.
Z: That's why I suggested that Einstein may have got it right in the title of his 1905 paper: the idea of "particles of light" is merely a heuristic point of departure.
J: I have no idea how that is relevant. There is no competing explanation of the fact of dark energy free of excess baggage - none as parsimonious as what I suggest using only elementary battle-tested physics..
Z: But you are saying in effect that dark energy is a frame artifact.
J: The quantum vacua and their excited state profiles at least for photons are dependent on the acceleration of the detectors - Unruh effect. In the case of charged spinors we need to excite fermion-antifermion pairs out of the zero point vacuum polarization to preserve charge conservation laws. When we write
g00 = 1 - /\r^2 static LNIF
that is frame aka detector dependent
as is
g00 = 1 in the FRLW co-moving detector representation http://arxiv.org/pdf/0803.2701v2
Z: No question that you are not the only one following this approach. For example you showed us the Gibbons-Hawking paper. So if there is a problem with this it will also be a problem with the reasoning in the Gibbons-Hawking paper.
I think you are missing some subtleties here. The mere fact that differently accelerating detectors interact differently
with the vacuum does not necessarily mean that they are "seeing" different vacuums. It's still possible to explain this
as the result of different objective physical interactions between the detectors and the vacuum.
J: The Rev Mod Phys reference http://arxiv.org/pdf/0710.5373v1 I gave you shows all the detailed quantum field theory machinery behind what I said. Indeed, no one in the field questions that much.
Z: In fact many such questions of this sort have been raised about the Unruh model. Part of the purpose of review articles
like Crispino's is to deal with such objections. They say that the excitation state of a quantum field is inherently frame dependent, regardless of the nature of the physical detectors and regardless of the nature of any physical interaction of the detectors with the vacuum. They argue that such frame dependence is built into the field quantization procedure on a more abstract level.
J: You are making a difference that does not make a difference. While the precise design of this or that detector is not relevant so long as it works, you must have some kind of detector because physics is about what detectors measure - or can in principle measure. If the physics cannot be done in terms of gedankenexperiments where the rubber touches the ground then it's not good physics. It may be good mathematics masquerading as physics. If it does not help an experimentalist then it is essentially worthless as physics.
Z: Which leads me to conclude that field quanta are not physical objects. And yet they are supposed to carry matter/energy
through the vacuum.
J: Your classical concept of physical objects is what is obsolete especially if we are merely back from the future hologram image computations in a virtual reality. ;-)
Z: So if Crispino et al. are correct, this conceptual problem is built into the field quantization model from the get-go. It's certainly not a criticism specifically about your Wheeler-Feynman model. OK, then what exactly is the argument against excitation of on-mass-shell quanta out of the vacuum by objective physical interaction with dynamically accelerating detectors? Should be easy to explain, since you clearly consider the answers here to be obvious.
J: Huh? I showed you the numbers! What don't you get?
Z: This is not simply about the numbers.
J: For me right now it's all about numbers. I am not interested in some airy fairy fantasy in la la land. We have a problem Houston. We measure hc/RH^2Lp^2 dark energy density accelerating the universe, whilst our best theories including sting theory (pun intended) predict hc/Lp^4 or maybe smaller, but still much too large.I am explaining hc/RH^2Lp^2 here - that is the point here. Off-topic tangents are noise in the signal here.
Z: If Crispino et al. have it right, in any QFT formulated in Minkowski spacetime, field quanta are inherently frame dependent. They are not physical objects. The field as a whole may be a physical object, but not the excitation states of the field. This is what was originally proposed by Davies by analogy with Hawking radiation in his 1974 paper:
http://cosmos.asu.edu/publications/papers/ScalarParticleProductionInSchwarzchild%2015.pdf
This was followed up by Unruh in his Physical Review D paper. As Crispino et al. remark, these proposals generated considerable perplexity among physicists.
J: Sure - but stay on point, which is to make some kind of sense of hc/RH^2Lp^2 .
To summarize where things stand at the moment in my opinion.
using standard GR starting from the static LNIF representation of the de Sitter metric to which we are evolving
g00 = 1 - /\r^2
g(r) = c^2VNewton,rg00^-1/2 --> 2c^2/\r(1 - /\r^2)^-1/2 ---> c^2/\^1/4(/\^-1/2 - r)^-1/2 ---> infinity classically at our future horizon r = /\^-1/2
The Unruh temperature/energy per degree of freedom is
kBTUnruh = hg/c ---> hc/\^1/4(/\^-1/2 - r)^-1/2
Z: OK. And in Unruh's model the vacuum thermal distribution is clearly frame dependent.
J: But the detector's proper acceleration is a tensor.
Using the Planck cutoff
(/\^-1/2 - r) = Lp = 10^-33 cm
/\ = 1/RH^2 = 10^-56cm^-2
kBTUnruh = hg/c ---> hc/\^1/4(/\^-1/2 - r)^-1/2 = hc(RHLP)^-1/2 ~ 10^-2710^10/(10^2810^-33)^1/2 ~ 10^-1710^3 ~ 10^-14 ergs ~ 10^-2ev
much too small for a real electron-positron plasma to be pulled out of the vacuum, but just right for the dark energy density from Planck's law
energy density = sigmaT^4 ---> hc/RH^2LP^2
Z: OK so now your model for dark energy is an Unruh radiation field?
J: Yes, but it must come back from our future event horizon! Area of our past particle horizon will be too small where-when our past light cone intersects it. This can't be a mere random coincidence in my opinion.
Z; If the numbers come out right it's certainly enough to launch an investigation.
J: You got that right Bhubba! Meantime the Pundits don't get it yet. However, if we think of the electron as a Bohm hidden variable Kerr-Newman black hole with roughly gravity radius 10^-56 cm and use that as the cut-off we get a large enough Unruh temperature of black body photons to pull virtual electron-positron pairs out of the vacuum - even virtual quark-antiquark pairs i.e. charged mesons.
i.e. 10^-17/(10^2810^-56)^1/2 = 10^-3 ergs = 10^9 ev ~ nucleon mass/energy
Z: OK I think this is moving too fast for me.
J: Faster than the speeding photon.
Poor Earthman! ;-)
Z: I have. I read the Gibbon-Hawking paper and Unruh's stuff. And I don't see any argument against a covariant
treatment of the Unruh effect in terms of objective physical interactions of accelerating detectors with the
EM vacuum.
J: Who cares? Of course it's covariant. The proper acceleration of the detector is a GCT first-rank tensor! Your question is trite. It's obviously covariant.
Z: True but irrelevant to what I'm talking about now. What I'm talking about now -- and what Crispino at al. are talking
about -- is the *inherent* frame dependence of field quantization in Minkowski spacetime.
J: It's even worse when you add curvature & torsion.
Z: So OK if Crispino et al. are correct, you're off the hook -- this is all built into canonical field quantization procedures.
J: g^u(detector) = d^2x^u(detector)/ds + (LC)^uvw(observer)(dx^v(detector)/ds)(dx^w(detector)/ds)
Z: Jack, the review article YOU POSTED on Unruh raises exactly these kinds of points. And answers them. And they agree with me that there has been much confusion among physicists about this topic. The whole Davies-Unruh model is based on an analogy between Hawking radiation from black hole horizons, and the supposed Unruh radiation from Rindler horizons. But a black hole horizon is a physical object, whereas a Rindler horizon is a frame artifact. So there is a real conundrum there.
J: Not at all. The Rindler horizon is a property of the accelerating detector independent of its design and composition so long as it detects photons.
Z: However, it is not specific or peculiar to your proposal.
J: 1) is the future horizon a total Wheeler-Feynman absorber? Hoyle and Narlikar say yes independently of the Unruh effect.
Z: OK, but The Devil is in the details here.
J: Keep Nick Herbert out of this. ;-)
Z: I assume here you are talking about an asymptotically de Sitter universe?
J: Yes, I am talking about Tamara Davis's model.
2) why is the dark energy density hc/RH^2LP^2 and not hc/LP^4 as naive quantum field theory demands?
Z: OK, good question.
J: To which I assert I have a good answer - better than anyone else's answer as far as I know.
Z: My question has been answered: field quanta are not physical objects. They are inherently frame dependent,
regardless of the nature of any possible interaction of dynamically accelerating detectors with the vacuum. And
this is all built into the canonical field quantization procedure carried out in Minkowski spacetime.
J: Glad you are happy but that question was not of interest to me - I already accepted that is the case.