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Re: Uncertainty principle and an elementary exercise with logs



Jack,
This doen't seem to be about the Uncertainity principle but which
"picture" of Quantum Mechanics we should be using. The Heisenberg picture
says that the operator changes with time, while Schrodinger says the state
vector changes with time. That means that the active picture of
Schrodinger is correct according to this paper (which I have not read).
This is the same difference as rotating a vector (active) or the
coordinate system (passive). It seems to me that some more thought is
required especially because momentum and position is a conjugate pair of
variables that seems to be coupled to me. Just my $0.02 about that.
Luckily according to QM, I have a finite probability of being right.


Sam Held


On Wed, 9 Sep 1998, JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439 wrote:

Hi all-
This deals with two different unrelated topics.
1. Anyone teaching QM at any level should see the News and Views article
by Peter Knight, "Where the Weirdness Comes from" in Nature for 3 Sept
1998, p. 12. Knight discusses an experimental determination that
Heisenberg's explanation of measurement disturbances is incorrect. That
is, in the two slit experiment, it is not the momentum kick from
observing which path was followed by a particle that destroys the
interference pattern. The correct view is given by Schroedinger's
entangled state approach.
The point appears to be that QM is the physics of coherence,
and QM effects go away once coherence is destroyed.

2. For those teaching elementary courses, there is a nice exercise
in log-log plotting in Phys Rev Lett 80 (1998) 5498 in table I. The
article does not give a math relationship between the number of
W-boson events and the transverse momentum. Let your students plot
the data and find that the event rate falls as p^-3, a new result in
physics.

Regards,
Jack

"I scored the next great triumph for science myself,
to wit, how the milk gets into the cow. Both of us
had marveled over that mystery a long time. We had
followed the cows around for years - that is, in the
daytime - but had never caught them drinking fluid of
that color."
Mark Twain, Extract from Eve's
Autobiography