124 reputation
13
bio website
location
age
visits member for 1 year, 11 months
seen Feb 14 '13 at 16:49

Jan
23
awarded  Enthusiast
Dec
31
answered How exactly do superstrings reduce the number of dimensions in bosonic string theory from 26 to 10 and remove the tachyons?
Dec
30
awarded  Supporter
Dec
27
comment The Double Slit Experiment - delayed measurement
Ah, thank you. Done.
Dec
27
awarded  Editor
Dec
27
revised The Double Slit Experiment - delayed measurement
added 3 characters in body
Dec
27
comment The Double Slit Experiment - delayed measurement
I probably should have been clearer in my wording. I intended to define the term "well constructed" in the context of this particular question as an experiment such that the existence of path information completely destroys the interference pattern. Indeed, this was to avoid the exact situation that your link describes. Obviously, the interference pattern need not constitute a perfect momentum measurement nor need the path information constitute a perfect position measurement so it is feasible to get both. Perhaps I should have said "well constructed quantum eraser experiment."
Dec
27
answered The Double Slit Experiment - delayed measurement
Dec
27
comment Why do many people say vector fields describe spin-1 particle but omit the spin-0 part?
For our purposes you should completely disregard what the (1/2,1/2) irrep decomposes into under SO(3). Yes, it is true that this decomposition must always contain the correct spin representation, but that is not necessary to understand the spin. The point is that if you take a (1/2,1/2) field like the photon and calculate the creation and annihilation operators you will find that these operators always create spin 1 single particle states and never spin 0 states. That's why we say that the (1/2,1/2) irrep is spin 1.
Dec
26
comment Why do many people say vector fields describe spin-1 particle but omit the spin-0 part?
So, you can see that a massive vector field (Lorentz group) is spin 1 because it creates single particle states that transform in the spin 1 representation of the little group SO(3), not because it decomposes into the spin 1 representation under the SO(3) subgroup.
Dec
26
comment Why do many people say vector fields describe spin-1 particle but omit the spin-0 part?
Ok, I see what is going on here. You have to differentiate between representations of the Lorentz group and representations of the Poincare group. Of course you are right that the spin is defined by the representation of the little group. However, to determine the spin of a field you do not decompose the representation of the Lorentz group into representations of the little group. The little group is used to construct representations of the Poincare group in which single particle states transform.
Dec
25
awarded  Teacher
Dec
25
answered Why do many people say vector fields describe spin-1 particle but omit the spin-0 part?
Dec
25
answered Are branes in 4D-spacetime moving, or are they static?