On 11/5/2024 1:26 AM, Alan Grayson wrote:


On Tuesday, November 5, 2024 at 12:27:55 AM UTC-7 Russell Standish wrote:

    On Mon, Nov 04, 2024 at 10:12:39PM -0800, Brent Meeker wrote:
    >
    >
    >
    > On 11/4/2024 9:47 PM, Alan Grayson wrote:
    >
    >
    > On an unrelated issue, I recall your mention that wrt the S. Cat
    thought
    > experiment, there is no
    > operator which has Alive and Dead as eigenvalues. IMO, this
    implies that
    > the S. Cat thought
    > experiment just doesn't fit into any quantum thought experiment.
    I then
    > realized that the P
    > operator for momentum must have a real value for its eigenvalues
    since it's
    > Hermitian, BUT
    > how can a real value represent momentum, which is a vector?  TY, AG
    >
    > The eigenvector would be momentum.
    >

    Sorry Brent - the measured momentum values are still eigenvalues.

    Pick 3 orthogonal directions to measure the momentum, say x, y and z.

    Then the momentum operators are -iℏ∂/∂x, -iℏ∂/∂y and -iℏ∂/∂z, and
    the 3 eigenvalues are the 3 components of momentum.

    One could also write it in vector form iℏ∇, in which case the
    operator
    has a vector-valued eigenvalue.


I don't think this is correct. Quantum operators are chosen to be Hermitian, that is, self-adjoint IIRC, so that their eigenvalues will be real. This is something that can be proven. So the question remains; how can a real eigenvalue be a measured momentum, which
is a vector? AG
https://en.wikipedia.org/wiki/Momentum_operator

Brent

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