Thursday, April 26, 2012

Pauli principle and Color charge

Wolfgang Ernst Pauli (1900 – 1958)

Wolfgang Ernst Pauli was an Austrian theoretical physicist and one of the pioneers of quantum physics. In 1945, after being nominated by Albert Einstein, he received the Nobel Prize in Physics for his "decisive contribution through his discovery of a new law of Nature, the exclusion principle or Pauli principle," involving spin theory, underpinning the structure of matter and the whole of chemistry. wikipedia

The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions (particles with half-integer spin) may occupy the same quantum state simultaneously.

A more rigorous statement is that the total wave function for two identical fermions is anti-symmetric with respect to exchange of the particles. The principle was formulated by Austrian physicist Wolfgang Pauli in 1925.

Color charge
Professor Oscar W. Greenberg (1932) University of Maryland
Shortly after the existence of quarks was first proposed in 1964, Oscar W. Greenberg introduced the notion of color charge to explain how quarks could coexist inside some hadrons in otherwise identical quantum states without violating the Pauli exclusion principle.

O.W. Greenberg, Spin and  Unitary-Spin Independence in a Paraquark Model of Baryons and Mesons, Phys. Rev. Lett. 13, 598-602 (1964)

The theory of quantum chromodynamics has been under development since the 1970s and constitutes an important component of the Standard Model of particle physics

In particle physics, color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD).
Color charge has analogies with the notion of electric charge of particles, but because of the mathematical complications of QCD, there are many technical differences.

The "color" of quarks and gluons is completely unrelated to visual perception of color. Rather, it is a name for a property that has almost no manifestation at distances above the size of an atomic nucleus.

The term color was chosen because the abstract property to which it refers has three aspects, which are analogized to the three primary colors of red, green, and blue.

By comparison, the electromagnetic charge has a single aspect, which takes the values positive or negative.

No comments:

Post a Comment