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Page title[edit]

Should'nt this be named spin operator? Karol 19:40, 28 October 2005 (UTC)


Recent edits seem to suggest that all fermions have spin of 1/2. However, I was under the impression that fermions have half-integer spin (not necessarily 1/2).--GregRM 02:51, 16 March 2006 (UTC)

You are right. What I really meant is that all fundamental particles that are fermions have spin 1/2. Of course, composite particles can have any integer or half integer spin. I have changed the article accordingly. Thanks for the catch. Grokmoo 03:51, 16 March 2006 (UTC)
It is still slightly unclear. The definition says

Fermions have half-integer spin.
Spin-½ particles constitute an important subset of such fermions.

Assuming that an important subset is strictly a subset, one derives that while having half-integer spin implies being a spin-½ particle, the opposite is not necessarily true. That, in turn, reveals the difference between half-integer and ½, after possibly excluding that the dash should be interpreted as a minus. Would it be overwhelmingly pedantic to state that Spin-½ is the property of particles whose spin is ½? Hmm... I'll do it. ale (talk) 13:41, 3 May 2009 (UTC)

Unclear use of dash[edit]

After reading this article, some people may be confused by the expression 'spin-1/2' - in that does it mean a spin of negative half, or positive half (with a dash just for linkage)? This should probably be redefined or at least explained in the article. Harabanar (talk) 11:21, 15 September 2009 (UTC)

Heisenberg picture[edit]

How does the spin operator look in the Heisenberg picture?


How should Spin-½ be pronounced..? "half-spin", "spin minus a ½"..? For outsiders it is not obvious. --Harabanar (talk) 11:21, 15 September 2009 (UTC)—Preceding unsigned comment added by Harabanar (talkcontribs) 08:06, 15 September 2009 (UTC)

In the CRC Handbook, the spin of 4Be8 is given as zero. Then the spin of 4Be9 is given as -3/2. And the spin of 5B10 is given as +3. What is that supposed to tell me? WFPM (talk) 03:06, 14 November 2008 (UTC)

That nuclei are composite particles. Eutactic (talk) 02:47, 12 October 2010 (UTC)

Wave function[edit]

Can we put the wave function of the electron in the article? Jackzhp (talk) 16:36, 23 October 2013 (UTC)

Spin as consequence of ...[edit]

This claim seems not true, spin 1/2 seems to be explained by Heisenberg by the 1st time. Jackzhp (talk) 20:17, 23 October 2013 (UTC)

Mathematical Description Section[edit]

This sections sounds as if it was written by a non-native English speaker, so I'll try to clean it up. It could also use some fleshing out as it's rather sparse at the moment but covers a topic that's critical for undergraduate studies in physics. — Preceding unsigned comment added by ArchetypeRyan (talkcontribs) 04:36, 7 November 2013 (UTC)

Also, I would be very careful of citing McMahon's book QFTD. His publisher McGraw-Hill Education is notorious for farming out much of the production work on its books to Conveo, and the proof-reading tends to be abysmal, with dozens of errors. We removed McMahon's book Quantum Mechanics Demystified from the References in the article Angular momentum operator for just this reason: hundreds of typos.Edgeorge (talk) 00:01, 1 February 2014 (UTC) Duncan

Complex Phase[edit]

Hope i haven't annoyed anyone, but I just added the following para

In terms of more direct evidence, physical effects of the difference between the rotation of a spin-half particle by 360° as compared with 720° have been experimentally observed in classic experiments [5] in neutron interferometry. In particular, if a beam of spin-oriented spin-half particles is split, and just one of the beams is rotated about the axis of its direction of motion and then recombined with the original beam, different interference effects are observed depending on the angle. In the case of rotation by 360°, cancellation effects are observed, whereas in the case of rotation by 720°, the beams are mutually reinforcing.

- as this section seemed misleading or murky without something like that. Doubtless folk will correct me if I slipped up. Reflection (talk) 21:07, 9 December 2016 (UTC)