Accelerator Experiments, Detector Mass & Gravity Effects

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In summary: Or vice versa."In summary, the presence of an observer's momentum affects the way in which a foliation can be defined.
  • #1
Thomas Larsson
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In order not to further irritate Marcus, let us move this off-topic discussion from the Rovelli thread.

Careful said:
** In conventional QM, time just marches on independent of what happens. Time must operationally be defined by ticks on the observer's clock, and thus the observer does not accelerate.**

? There is no problem whatsoever in defining QFT with respect to (non-uniformly) accelerating observers (and bending the foliation according to local eigentime - as long as one does not encounter focal points).

Whether the foliation is bent or not has nothing to do with my argument. By talking about a foliation, you are making a hidden assumption about classical observers. However, since the observer's trajectory is a quantum variable, it can only be specified if we leave the observer's momentum completely undetermined. Or vice versa. This means that the foliation itself is subject to quantum fluctuations, which is the essential physical novelty.

Careful said:
** This is no problem we observe an electric phenomenon, say. Then F = ma = qE, where q is the observer's charge and E the electric field generated by the system. That q and E are non-zero and a = 0 is OK, since m = infinity is a good approximation to reality. **

? The m in the Newton formula is the physical mass and not the bare mass, for an electron that is still the very tiny number of 10^{-30} kilo at least when it moves smaller than c wrt an inertial observer. You can find such information in Eric Poisson, ``An introduction to the Lorentz Dirac equation´´ gr-qc/9912045 where such understanding is offered at a classical level.

In typical accelerator experiments, the detectors weigh several tonnes, and measurements are related to the detector's rest frame. The assumption that such a detector does not recoil at all is an excellent approximation, which is implicit in the assumption that the detector follows a sharp, classical trajectory. However, it is an approximation, which amounts to replacing several tonnes by infinity. When gravity is turned on, this becomes a problem, because an infinite mass will immediately collapse into a black hole. This is an essential difference between gravity and other interactions.
 
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  • #2
**
Whether the foliation is bent or not has nothing to do with my argument. By talking about a foliation, you are making a hidden assumption about classical observers. However, since the observer's trajectory is a quantum variable, it can only be specified if we leave the observer's momentum completely undetermined. Or vice versa. This means that the foliation itself is subject to quantum fluctuations, which is the essential physical novelty. **

Don't you think I realize that ?? :grumpy: Moreover, I still do not agree that it is some kind of foliation which is subject to fluctuations in your framework (fix the ontology of your t sensibly). By referring to the standard QFT result I merely asserted that you should obtain the latter result for ``macroscopic´´ observers in your framework. And for that you do not have to take the sick limit M -> infinity which indeed causes trouble for gravity. You might try to establish such correspondence at the statistical level, by considering the deterministic evolution of expectation values of the worldline operators (a la Ehrenfest) exactly like some people try to take the ``classical limit´´ of quantum mechanics (it came as a surprise to me that you did not realize that). This answers immediatly the rest of your message. Frankly, the idea of fluctuating foliations is not a novetly either, your work at the Hamiltonian level (again fix the ontology of t) however is (to my knowledge). That is why I said that the paper interesting even if it turns out to be entirely wrong.
 
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  • #3
Careful said:
**
This means that the foliation itself is subject to quantum fluctuations, which is the essential physical novelty. **

Don't you think I realize that ?? :grumpy:

But you also wrote

"? There is no problem whatsoever in defining QFT with respect to (non-uniformly) accelerating observers (and bending the foliation according to local eigentime - as long as one does not encounter focal points)."

Thus you seem to be saying that there is no problem whatsoever in defining QFT over a foliation which itself is subject to quantum fluctuations. This statement may raise some eyebrows. At least I disagree.

It is of course widely expected that the foliation is quantized on quantum gravity, but I am only aware of one more suggestion how to implement this technically, namely the histories approach of Isham, Linden and in particular Savvidou, see e.g. http://www.arxiv.org/abs/quant-ph/0110161 . There is some overlap between my approach and theirs, but I am not sure about the exact status of their work. Anyway, a quantum foliation is certainly *not* part of standard canonical QFT.
 
  • #4
**But you also wrote

"? There is no problem whatsoever in defining QFT with respect to (non-uniformly) accelerating observers (and bending the foliation according to local eigentime - as long as one does not encounter focal points)."

Thus you seem to be saying that there is no problem whatsoever in defining QFT over a foliation which itself is subject to quantum fluctuations. This statement may raise some eyebrows. At least I disagree.
**

I repeat myself : all I said is that there is no problem in defining QFT over a foliation corresponding to accelerated observers. OBVIOUSLY, I consider the observer classical here, and I alluded already to the unavoidable problem which raises in quantum theory for the foliation - and that are the focal points. Moreover, I implied by this that any theory which treats the foliation as quantum obviously needs to incorporate the possibility for acceleration.


** namely the histories approach of Isham, Linden and in particular Savvidou, see e.g. http://www.arxiv.org/abs/quant-ph/0110161 . There is some overlap between my approach and theirs, but I am not sure about the exact status of their work. **

I know that approach.

**Anyway, a quantum foliation is certainly *not* part of standard canonical QFT. **

right, but in path integrals that all becomes much easier as I said in the beginning. This conversation is finished.
 
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  • #5
a courteous good morning to you gentlemen (pacific time)
fascinating discussion
glad you made a thread for it
 

1. What is an accelerator experiment?

An accelerator experiment is a type of scientific experiment that involves using powerful accelerators, typically particle accelerators, to create and study particles at high energies. These experiments help scientists understand the fundamental properties of matter and the forces that govern the universe.

2. How does a particle accelerator work?

A particle accelerator works by using electromagnetic fields to accelerate particles to high speeds. The particles are then collided with a target or with each other, creating a burst of energy that can be studied by detectors. This allows scientists to study the particles and their interactions in detail.

3. Can accelerator experiments help us understand gravity?

Yes, accelerator experiments can provide valuable insights into the nature of gravity. By studying the behavior of particles at high energies, scientists can test the predictions of different theories of gravity, such as Einstein's theory of general relativity. These experiments can also help us understand the role of gravity in the early universe.

4. How does the mass of a detector affect accelerator experiments?

The mass of a detector can affect accelerator experiments in several ways. The larger the mass of the detector, the more energy is required to accelerate particles to high speeds. In addition, the mass of the detector can also affect the accuracy of measurements, as heavier detectors may be more susceptible to vibration and other external factors.

5. What are gravity effects in accelerator experiments?

Gravity effects in accelerator experiments refer to the influence of gravity on the behavior of particles at high energies. This can include the bending of particle trajectories due to the gravitational pull of large masses, such as Earth, as well as the effects of gravity on the overall energy and momentum of the particles being studied.

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