Can Color Singlets Be Formed for Baryons and Mesons?

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Discussion Overview

The discussion revolves around the conceptual understanding of forming color singlets for baryons and mesons, particularly in relation to their spin and isospin states. Participants explore the construction of these singlets within the framework of quantum chromodynamics (QCD) and the symmetry properties involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks to understand how to create a color singlet corresponding to baryons and mesons, referencing isospin and spin states.
  • Another participant explains that the completely antisymmetric color state of three quarks in the fundamental representation of SU(3) results in a color singlet.
  • A participant draws an analogy between color symmetry (red, green, blue) and flavor symmetry (up, down, strange), suggesting that a singlet can be formed from colors similarly to flavors.
  • One participant expresses confusion about constructing a proton wavefunction that is colorless while embodying spin 1/2 and isospin 1/2, questioning the role of a 'color' matrix in this process.
  • Another participant mentions that the state belongs to the tensor product space of single particle state spaces, which includes spin, isospin, color states, and spatial states.

Areas of Agreement / Disagreement

Participants present various viewpoints and explanations regarding the formation of color singlets, but there is no consensus on the specific methods for constructing wavefunctions that incorporate all necessary properties.

Contextual Notes

Limitations in the discussion include potential missing assumptions about the mathematical formalism involved in constructing wavefunctions and the dependence on definitions of color and flavor symmetries.

nigelscott
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I am trying to conceptually understand how form a color singlet for baryons and mesons. For example, the Wikipedia article http://en.wikipedia.org/wiki/Isospin shows how to construct the proton and neutron states in terms of isospin and spin. How does one create a color singlet corresponding to these states?
 
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Each of the valence quarks carry a colour charge. The completely anit-symmetric colour state containing three objects in the fundamental (3) representation of SU(3) is a colour singlet.
 
The color (r,g,b) symmetry is pretty much like the flavor symmetry for 3 flavors (u,d,s)...
So you form a singlet out of colors, in the same way you can form a singlet of three flavors (which is antisymmetric) ...
 
yes, I understand the formation of the color singlet from 3 x 3 x 3 = 1 + 8. What I don't understand is how you create a proton wavefunction that embodies spin 1/2, isospin 1/2 and is colorless. In the Wikipedia article, the wf is the product of 3 matrices. To create a colorless photon do you just multiply these by some kind of 'color' matrix that produces the desired result?
 
The state belongs to the tensor product space of the single particle state spaces, which in turn are tensor products of the spin, isospin, and colour states, as well as with the spatial state.
 

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