On 4/15/2020 10:37 PM, Alan Grayson wrote:


On Wednesday, April 15, 2020 at 10:49:45 AM UTC-6, smitra wrote:

    On 15-04-2020 04:20, Alan Grayson wrote:
    > On Tuesday, April 14, 2020 at 4:28:23 PM UTC-6, Bruce wrote:
    >
    >> On Wed, Apr 15, 2020 at 2:07 AM Jason Resch <[email protected]>
    >> wrote:
    >>
    >>> There has been controversy [1] in the meaning/interpretation of
    >>> the Time-Energy uncertainty relation in quantum mechanics, but
    >>> relatively none regarding the meaning of the position-momentum
    >>> uncertainty.
    >>>
    >>> However, can these not be viewed equivalently in terms of a
    >>> 4-dimensional space time?
    >>>
    >>> For example, I have seen some describe mass/energy as momentum
    >>> through time. Massless particles don't age, and have no momentum
    >>> through time.
    >>>
    >>> Similarly, cannot a point-in-time measurement be viewed as a
    >>> measurement of position in the time dimension?
    >>>
    >>> In my view, you can go from the position-momentum uncertainty to
    >>> the time-energy uncertainty simply by flipping the time-space
    >>> orientation. Is this valid? Is there something I am missing?
    >>
    >> You are missing the fact that energy is bounded below, whereas
    >> momentum can take on any value between plus and minus infinity.
    Time
    >> is not an operator in quantum mechanics.
    >>
    >> Bruce
    >
    > Isn't there a valid interpretation/ application of the time-energy
    > uncertainty relation in the context of emission of radiation? If
    so,
    > what is it? TIA, AG
    >
    The rigorous versions of these interpretations involve having some
    physical object included in the system that serves as a clock. So, if
    you actually perform a measurement involving time, then the measured
    time is represented by a physical clock. So, by including a quantum
    mechanical description of a simplified model clock, you then do
    get an
    observable for the measured time, despite the fact that there is no
    observable that allows you to measure the parameter t in the
    Schrodinger
    equation.

    Saibal


Can you give a concrete example where the time-energy form of the UP can be applied to? I once had an example, but can't recall what it was. TIA, AG

It's used all the time in interpreting collision spectra in particle physics.  A sharp resonant line in the energy spectrum implies the generation of a long live particle, while a broad line implies a short lifetime.

Brent

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