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11h
asked How does Dirac show that $\langle B|\bar{\bar{\alpha}}|P\rangle\;=\; \overline{\langle P|{\bar{\alpha}}|B\rangle}\;=\; \langle B|{\alpha}|P\rangle$?
Aug
26
accepted Can relativistic kinetic energy be derived from Newtonian kinetic energy?
Aug
25
comment Explanation for $E~$ not falling off at $1/r^2$ for infinite line and sheet charges?
@RonMaimon now that you've had a long rest, does this answer still make sense to you honestly?
Aug
24
comment Is there a “forwards” and “backwards” in one dimension?
So a magnitude can be negative?
Aug
24
accepted Is there a “forwards” and “backwards” in one dimension?
Aug
24
comment Is there a “forwards” and “backwards” in one dimension?
@HDE226868 sure you can. But maybe that isn't a true one dimensional space as defined by a physicist or mathematician, and a direction paramaterized by two discrete symbols +,- has been added.
Aug
24
asked Is there a “forwards” and “backwards” in one dimension?
Aug
24
comment Physical reason for Lorentz Transformation
You're only looking at a light-like interval; you need to show how invariance of this implies invariance of space-like and time-like intervals also.
Aug
20
comment Rotation axis of a rigid body
+1 all this work, and just one lousy up-vote?
Aug
19
comment Why should multiplication of a ket vector by a complex number change only its “direction”?
@ACuriousMind A vector multiplied by a negative real number changes its direction, yes? How are we to interpret multiplying it by a complex number?
Aug
19
revised Why should multiplication of a ket vector by a complex number change only its “direction”?
improved context
Aug
19
comment Why should multiplication of a ket vector by a complex number change only its “direction”?
@Nathan I'm looking for an answer in the spirit of Dirac talking vaguely about vectors in an infinite dimensional space up to this point. I guess this will become clearer later on in the book, but Dirac seems to suggest this statement is obvious for physical/mathematical reasons.
Aug
19
asked Why should multiplication of a ket vector by a complex number change only its “direction”?
Aug
19
comment When is it useful to distinguish between vectors and pseudovectors in experimental & theoretical physics?
Cool, is there a book you can recommend which goes into this in more detail?
Jul
23
comment What is a tensor?
A tensor is a geometrical object whose components transform like that of a tensor.
Jul
13
awarded  Yearling
Jul
11
comment How does the speed of electrons change around a circuit?
The drift velocity is typically around a few centimeters/hour.
Jul
2
awarded  Curious
Jun
27
awarded  Popular Question
Jun
13
comment Why Lorentz Transformation in Special Relativity has to be like this?
You've thought about this before, right?