Physics:Quantum fermion
A quantum fermion is a particle with half-integer spin that obeys Fermi-Dirac statistics. Fermions have antisymmetric many-particle wavefunctions, so identical fermions cannot occupy the same one-particle quantum state. This rule gives matter much of its structure, from atomic shells to degenerate stars.[1][2]
Spin and statistics
The spin-statistics connection links half-integer spin with fermionic exchange behavior in relativistic quantum theory. Exchanging two identical fermions changes the sign of the many-body wavefunction. The resulting Pauli exclusion principle is not an ordinary force; it is a constraint on the allowed quantum states.[3]
Elementary and composite fermions
Elementary fermions include quarks and leptons. Composite systems can also behave as fermions when their total spin is half-integer, as in protons, neutrons, many nuclei, atoms, and quasiparticle excitations in condensed matter.
Physical consequences
Fermion statistics explain the periodic structure of atoms, electron degeneracy pressure, band filling in solids, and the stability of ordinary matter. In particle physics, fermion flavor, chirality, and mass mixing are central to weak interactions, neutrino oscillations, and matter-antimatter studies.[4]
See also
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References
- ↑ Pauli, Wolfgang (1940). "The Connection Between Spin and Statistics". Physical Review 58 (8): 716-722. doi:10.1103/PhysRev.58.716.
- ↑ Particle Data Group (2022). "Review of Particle Physics". Progress of Theoretical and Experimental Physics 2022 (8): 083C01. doi:10.1093/ptep/ptac097.
- ↑ Peskin, Michael E.; Schroeder, Daniel V. (1995). An Introduction to Quantum Field Theory. Addison-Wesley. ISBN 978-0-201-50397-5.
- ↑ Griffiths, David J. (2008). Introduction to Elementary Particles (2nd ed.). Wiley-VCH. ISBN 978-3-527-40601-2.
Source attribution: Fermion