How does a spinor affect a wave function?

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Discussion Overview

The discussion revolves around the role of spinors in wave function solutions, particularly in the context of quantum mechanics. Participants explore how spinors interact with spatial components of wave functions and the implications for particles with spin, including effects on systems like electrons in atoms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants inquire about how spinors affect wave function solutions and the differences in output due to spin.
  • One participant notes that the wave function of a particle with spin combines a spatial component and a spinor, referencing the Dirac equation.
  • Another participant highlights that spin allows for states with two electrons sharing the same spatial wave function, which has significant implications for chemistry, specifically in systems like the helium atom.
  • A later reply elaborates that a spinor wave function consists of multiple spatial components, specifically four for a single-electron solution of the Dirac equation, and discusses the algebraic properties that define a spinor.
  • One participant suggests reframing the question to focus on what characterizes a wave function solution as a spinor, emphasizing that the association of spatial wave functions with spinors does not alter the spatial wave functions themselves.

Areas of Agreement / Disagreement

Participants express varying perspectives on the nature of spinors and their relationship to wave functions, indicating that multiple competing views remain without a clear consensus on the best way to frame the discussion.

Contextual Notes

Some limitations include the dependence on specific definitions of spinors and wave functions, as well as unresolved mathematical details regarding the properties and implications of spinors in quantum mechanics.

justpeeking
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How do spinors affect wave function solutions? Like how is the output different
 
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justpeeking said:
How do spinors affect wave function solutions? Like how is the output different
The wave function of a particle with spin is the composition of a spatial component and a spinor. See the Dirac equation, for example:

https://en.wikipedia.org/wiki/Dirac_equation
 
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justpeeking said:
How do spinors affect wave function solutions? Like how is the output different
Due to spin, you can have a state with two electrons with the same spatial wave function. It has dramatic consequences for chemistry, see e.g. https://en.wikipedia.org/wiki/Helium_atom.
 
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PeroK said:
The wave function of a particle with spin is the composition of a spatial component and a spinor. See the Dirac equation, for example:

https://en.wikipedia.org/wiki/Dirac_equation

Respecting your expertise and appreciating Demystifier's enlightening answer, nevertheless might a slightly more illluminating answer* to the question be:

A spinor wave function has multiple spatial components (four for a single-electron solution of the Dirac equation).

It is the algebraic properties of this multicomponent object that makes it a spinor.

In the case of Pauli's early phenomenological theory of spin, he developed spinors that had 2-complex components (just two complex numbers). These can be combined with spatial wave functions, as your own answer states, in a manner that is very clearly illustrated in Richard Fitzpatrick's article https://farside.ph.utexas.edu/teaching/qm/lectures/node51.html

So rather than ask "How ... spinors affect wave function solutions" it might be better to ask "what characterises a wave function solution as a spinor" (i.e. being components of a spinors doesn't change (affect) the spatial wave functions themselves, but rather associates them in such a way that the whole mathematical object is - has the properties of - a spinor.)

* OK - pedantic if you prefer
 
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