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basic_notions:spin [2018/03/28 08:51]
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basic_notions:spin [2019/11/29 13:13] (current)
129.13.36.189 [Concrete]
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 ====== Spin ====== ====== Spin ======
  
-<​tabbox ​Why is it interesting?​>  +<​tabbox ​Intuitive>  
-Spin is one of the most important ​[[basic_notions:quantum_numbers|quantum numbers]]. +One of the biggest discoveries in the last century was that elementary particles have spin, which is some kind of internal angular momentum. This was discovered by the famous ​[[experiments:stern-gerlach|Stern-Gerlach experiment]].
  
-In fact, it is so important ​that is responsible for the definition of the most important categories of [[advanced_notions:elementary_particles|elementary particles]]:+In abstract terms you can think about spin as a label that tells us how particles behave in experiments,​ exactly as the [[basic_notions:mass|mass]] or the electric [[basic_notions:charge|charge]]. For example, a particle with electric charge behaves different than one without in experiments and the same is true for spin.
  
 +There are particles with spin $0$, particles with spin $\frac{1}{2}$ and particles with spin $1$. For each of these different particle types we have a different [[:​equations|equation]]that describes their behavior.
  
-  * Particles with integer spin ($0,​1,​\ldots$) are called **bosons** and are responsible for the fundamental interactions. Examples are the photon, which is responsible for electromagnetic interactions or the gluons which are responsible for the strong interactions.  +----
-  * Particles with half-integer spin ($\frac{1}{2}$) are responsible for matter and are called **fermions**. Examples are electrons and quarks, which are the constituents of atoms.  +
- +
-<​blockquote>​According to the prevailing belief, the spin of the electron or of some other particle is a mysterious internal angular momentum for which no concrete physical picture is available, and for which there is no classical analog. However, on the basis of an old calculation by Belinfante [Physica 6, 887 (1939)], it can be shown that the spin may be regarded as an angular momentum generated by a circulating flow of energy in the wave field of the electron. Likewise, the magnetic moment may be regarded as generated by a circulating flow of charge in the wave field. This provides an intuitively appealing picture and establishes that neither the spin nor the magnetic moment are ‘‘internal’’—they are not associated with the internal structure of the electron, but rather with the structure of its wave field. +
-<​cite>​ [[http://​aapt.scitation.org/​doi/​abs/​10.1119/​1.14580|What is spin?]] by Hans C. Ohanian </​cite></​blockquote>​ +
- +
- +
- +
-**Important Related Concepts:​** +
- +
-  * [[advanced_notions:​helicity|]] +
-  * [[advanced_notions:​chirality|]] +
-  * [[advanced_tools:​spinors]] +
- +
- +
-<tabbox Layman> ​+
  
   * [[https://​medium.com/​starts-with-a-bang/​spin-the-quantum-property-that-should-have-been-impossible-40bd52548b22|Spin:​ The Quantum Property That Should Have Been Impossible]] by Paul Halpern   * [[https://​medium.com/​starts-with-a-bang/​spin-the-quantum-property-that-should-have-been-impossible-40bd52548b22|Spin:​ The Quantum Property That Should Have Been Impossible]] by Paul Halpern
   * https://​www.scientificamerican.com/​article/​what-exactly-is-the-spin/​   * https://​www.scientificamerican.com/​article/​what-exactly-is-the-spin/​
   * https://​www.forbes.com/​sites/​startswithabang/​2017/​11/​21/​spin-the-quantum-property-that-nature-shouldnt-possess/#​20a3df076349   * https://​www.forbes.com/​sites/​startswithabang/​2017/​11/​21/​spin-the-quantum-property-that-nature-shouldnt-possess/#​20a3df076349
-<​tabbox ​Student+ 
 + 
 +<​tabbox ​Concrete
 Spin is a quantum number like mass or like the electric charge. Spin has exactly the same origin as the other quantum numbers and is therefore not as strange as most people believe it to be.  Spin is a quantum number like mass or like the electric charge. Spin has exactly the same origin as the other quantum numbers and is therefore not as strange as most people believe it to be. 
  
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   * For the origin of spin, see http://​rickbradford.co.uk/​NoethersTheorem.pdf   * For the origin of spin, see http://​rickbradford.co.uk/​NoethersTheorem.pdf
   * [[http://​math.ucr.edu/​home/​baez/​spin/​spin.html|Spin]] by Michael Weiss   * [[http://​math.ucr.edu/​home/​baez/​spin/​spin.html|Spin]] by Michael Weiss
 +  * https://​arxiv.org/​abs/​1806.01121
  
  
- +<​tabbox ​Abstract
- +
- +
- +
- +
- +
-   +
-<​tabbox ​Researcher+
  
 <note tip> <note tip>
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 </​note>​ </​note>​
  
 +<tabbox Why is it interesting?> ​
 +Spin is one of the most important [[basic_notions:​quantum_numbers|quantum numbers]]. ​
  
 +In fact, it is so important that is responsible for the definition of the most important categories of [[advanced_notions:​elementary_particles|elementary particles]]:​
  
  
-<​tabbox ​Examples+  * Particles with integer spin ($0,​1,​\ldots$) are called **bosons** and are responsible for the fundamental interactions. ​Examples ​are the photon, which is responsible for electromagnetic interactions or the gluons which are responsible for the strong interactions.  
 +  * Particles with half-integer spin ($\frac{1}{2}$) are responsible for matter and are called **fermions**. Examples are electrons and quarks, which are the constituents of atoms. ​
  
---Example1#+<​blockquote>​According to the prevailing belief, the spin of the electron or of some other particle is a mysterious internal angular momentum for which no concrete physical picture is available, and for which there is no classical analog. However, on the basis of an old calculation by Belinfante [Physica 6, 887 (1939)], it can be shown that the spin may be regarded as an angular momentum generated by a circulating flow of energy in the wave field of the electron. Likewise, the magnetic moment may be regarded as generated by a circulating flow of charge in the wave field. This provides an intuitively appealing picture and establishes that neither the spin nor the magnetic moment are ‘‘internal’’—they are not associated with the internal structure of the electron, but rather with the structure of its wave field. 
 +<​cite>​ [[http://​aapt.scitation.org/​doi/​abs/​10.1119/​1.14580|What is spin?]] by Hans C. Ohanian </​cite></​blockquote>
  
-  
-<-- 
  
---> Example2:# 
  
-  +**Important Related Concepts:**
-<--+
  
 +  * [[advanced_notions:​helicity|]]
 +  * [[advanced_notions:​chirality|]]
 +  * [[advanced_tools:​spinors]]
 <tabbox FAQ> ​ <tabbox FAQ> ​
  
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 and[[http://​people.westminstercollege.edu/​faculty/​ccline/​courses/​phys425/​AJP_54(6)_p500.pdf| What is spin?]] by HC Ohanian ​ and[[http://​people.westminstercollege.edu/​faculty/​ccline/​courses/​phys425/​AJP_54(6)_p500.pdf| What is spin?]] by HC Ohanian ​
 +
 +An interesting alternative perspective was put forward by Hestenes in his paper [[http://​geocalc.clas.asu.edu/​pdf/​ZBW_I_QM.pdf|The Zitterbewegung Interpretation of Quantum Mechanics]]. In this paper he argues that spin arises due to the permanent zig-zag motion of electrons (and all other particles). This zig-zag motion is the result of permanent collisions with background Higgs bosons which cause chirality flips from left-chiral to right-chiral states.
 +
 +See also [[https://​arxiv.org/​abs/​1806.01121|How Electrons Spin]] by Charles T. Sebens
  
 <-- <--
basic_notions/spin.1522219905.txt.gz · Last modified: 2018/03/28 06:51 (external edit)