Infinite or undefined standard deviation in HUP

In summary, the canonical commutation rules for particles in curved space-time are valid only in flat space-time. Virtual particles do not have a dynamics, and so their velocities arbitrarily assigned mean nothing.
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nomadreid
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If we measure one conjugate variable in an uncertainty relation precisely , i.e., so its standard deviation is zero, then by the HUP the sd of the other one is either infinite or undefined. But what about the cases when the other conjugate variable has limits: e.g., there cannot be an infinite spread for momentum or energy? Is it then better to just say that the spread is undefined in this case?
 
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Canonically conjugate observables always have all reals in the spectrum, hence are unbounded and have no limits.
 
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A. Neumaier said:
Canonically conjugate observables always have all reals in the spectrum, hence are unbounded and have no limits.
OK. This raises the (certainly naïve) question: suppose we refer to the momentum of particle at a determined point. Since the point is precise, you have the infinite spectrum of momentum. However, beyond a certain momentum the particle has enough mass-energy at that point you end up with a black hole, making the point lose its exact value, which would mean that the spectrum of the momentum would not be able to go beyond that limit. Hence not infinite. There is obviously a basic flaw in my reasoning here, but what?
 
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nomadreid said:
OK. This raises the (certainly naïve) question: suppose we refer to the momentum of particle at a determined point. Since the point is precise, you have the infinite spectrum of momentum. However, beyond a certain momentum the particle has enough mass-energy at that point you end up with a black hole, making the point lose its exact value, which would mean that the spectrum of the momentum would not be able to go beyond that limit. Hence not infinite. There is obviously a basic flaw in my reasoning here, but what?
Canonical commutation rules for interacting particles are valid in flat space-time only. This excludes black holes.
 
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Ah, I overlooked that. Excellent point, thank you, A.Neumaier. That probably takes care of my other counterexamples. No superluminary virtual particles, then?
 
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Thank you, A.Neumaier, for that answer and the excellent link; my delay in answering was due to my reading through it. (I had a feeling I shouldn't have used the concept "virtual particles"...) Very interesting and well written, and there are a few things there that I intend to try to understand more thoroughly in the course of time.
(Wikipedia is a suitable target -- even in secondary school assignments, Wikipedia is not accepted as a reliable source due to the fact that the articles are not signed.) I was also trying to find out (online) what corresponds to the Uncertainty Relations (i.e., the canonical commutation rules) in curved space-time, but the discussions I found exceed my present level in the subject.
 

1. What is the Heisenberg Uncertainty Principle (HUP)?

The Heisenberg Uncertainty Principle (HUP) is a fundamental principle in quantum mechanics that states that it is impossible to simultaneously know the exact position and momentum of a particle. This means that the more precisely we know the position of a particle, the less precisely we can know its momentum, and vice versa.

2. What is the connection between HUP and standard deviation?

HUP is related to the standard deviation in that it sets a limit on how precisely we can measure certain physical properties of a particle. Standard deviation is a measure of the spread of a set of data, and in the case of HUP, it represents the uncertainty in our measurements due to the principles of quantum mechanics.

3. What does it mean for a standard deviation to be infinite or undefined in HUP?

When the standard deviation in HUP is infinite or undefined, it means that the uncertainty in our measurements is so large that it cannot be accurately quantified. This can occur when trying to measure both the position and momentum of a particle with extreme precision, as the uncertainty in one measurement will cause the uncertainty in the other to increase.

4. Can the uncertainty in HUP be reduced or eliminated?

The uncertainty in HUP is a fundamental principle in quantum mechanics and cannot be reduced or eliminated. However, by using advanced techniques and technology, scientists can minimize the uncertainty and make more precise measurements, but it will never be completely eliminated.

5. How does HUP impact scientific research and technology?

HUP has significant implications in various fields of science, including quantum mechanics, particle physics, and even technology. It limits the precision of measurements, which can affect the accuracy and reliability of scientific experiments and technological devices. However, it also opened the doors to new discoveries and advancements in fields such as quantum computing and cryptography.

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