Symmetries in particle physics
Symmetries in particle physics
Symmetries in particle physics
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<strong>Symmetries</strong><br />
Add<strong>in</strong>g two sp<strong>in</strong>-1/2<br />
Often, it is important to add sp<strong>in</strong>s<br />
Examples: bound states of sp<strong>in</strong>-1/2 fermions, sp<strong>in</strong>orbit<br />
coupl<strong>in</strong>g, etc..<br />
If two sp<strong>in</strong>-1/2 systems are added, the follow<strong>in</strong>g<br />
objects can emerge:<br />
Naively, they have sp<strong>in</strong> 1, 0, or -1, respectively.<br />
But: Need to dist<strong>in</strong>guish total sp<strong>in</strong> s and its<br />
projection onto the “measurement axis” s z<br />
(here, z has been chosen for simplicity)