Confusion about derivative operators

strangerep

Where does Dirac say that? If you're looking at his eq(11) on p89, what he
actually writes is
$$
\frac{d}{dq} \psi \rangle ~=~ \frac{d\psi}{dq} \,\rangle
$$
Note that absence of the ``##|##''. Dirac is using his own notation, but the
versions of that notation presented by more modern authors are different.

I checked a few other things in his book, including other parts of his notation.
IMHO, once one understands Dirac's notation properly, nothing is wrong.

@Tom: exactly what part of Dirac's explanation do you think is wrong??

Loro

I'm looking at eqn (12) on page 89, or (23) on page 91. I didn't really get why that is. Maybe it's as tom.stoer described?

And my main problem is actually with (46) on page 94 - that there isn't a minus there, as it would follow from sloppy calculations. This is mind-boggling to me!

Loro

Coming back to eqn 46 - I've just understood it. I thought there was a contradiction. Thanks everyone for giving me an impulse for thinking about all this more carefully.

I would still love to hear replies about [itex] \hat{\partial_q} |\psi> [/itex] though. It's very interesting, and thought-provoking.

tom.stoer

I think acting with derivative operators on kets does not make sense (but I have to check Dirac's book; up to now I only see what is written here in this thread; and this seems to be strange)