Wikipedia
The Pauli exclusion principle is the quantum mechanical principle that states that two identical fermions (particles with half-integer spin) cannot occupy the same quantum state simultaneously. In the case of electrons, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers: n, the principal quantum number, , the angular momentum quantum number, m, the magnetic quantum number, and m, the spin quantum number. For example, if two electrons reside in the same orbital, and if their n, , and m values are the same, then their m must be different, and thus the electrons must have opposite half-integer spins of 1/2 and -1/2. This principle was formulated by Austrian physicist Wolfgang Pauli in 1925 for electrons, and later extended to all fermions with his spin-statistics theorem of 1940.
A more rigorous statement is that the total wave function for two identical fermions is antisymmetric with respect to exchange of the particles. This means that the wave function changes its sign if the space and spin co-ordinates of any two particles are interchanged.
Particles with an integer spin, or bosons, are not subject to the Pauli exclusion principle: any number of identical bosons can occupy the same quantum state, as with, for instance, photons produced by a laser and Bose–Einstein condensate.
Usage examples of "pauli exclusion principle".
At normal temperatures, which are all well above a few Kelvins, electrons in a metal are thus distributed over a range of energies and momenta, as required by the Pauli Exclusion Principle.
The idea was this: when the star becomes small, the matter particles get very near each other, and so according to the Pauli exclusion principle, they must have very different velocities.
I think the Xeelee have found a way to suppress the Pauli Exclusion Principle, and so have found their way into a whole new regime of matter.
For bosons, however, the Pauli Exclusion Principle is irrelevant by definition—.
The classical properties of a fermion were having a spin of half a unit, obeying the Pauli exclusion principle (which kept all the electrons in an atom, and neutrons and protons in a nucleus, from falling together into the same, lowest-energy state), and responding to a 360-degree rotation by slipping 180 degrees out of phase with its unrotated version.
String theorists, however, wanted to make a fantastic leap beyond the revised standard model, to the Planck distance which was the smallest realm possible, the minimum quantum movement, which could not be decreased without contradicting the Pauli exclusion principle.
The officers' cabins were cubbyholes, the forecastle could be packed tighter only if the Pauli exclusion principle were repealed, the recreation facilities were valuable chiefly as a subject for jokes, and the less said about the galley the wiser.