Exchange interaction is the quantum mechanical effect of increasing or decreasing the energy of two or more fermions when their wave functions overlap. This energy change is the result of a force due to the identity of particles and exchange symmetry. Fig. ... In particle physics, fermions, (named after Enrico Fermi), are particles with semi-integer spin. ... This article discusses the concept of a wavefunction as it relates to quantum mechanics. ... // Computer programming In object-oriented programming, object identity is a mechanism for distinguishing different objects from each other. ...

For example, two electrons or two photons are indistinguishable - so their exchange must result in no observable changes. This mathematically results in Pauli exclusion principle for semi-integer spin particles and Bose-Einstein condensation for integer spin particles. Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925, which states that no two identical fermions may occupy the same quantum state. ... The terms spin and SPIN have several meanings, including those primarily discussed as spinning: For spin in sub-atomic physics, see spin (physics) For the stalled aircraft maneuver or any of several forms of loss of control in aircraft, see spin (flight) For the periodical, see Spin Magazine For the... A Bose-Einstein condensate is a gaseous superfluid phase formed by atoms cooled to temperatures very near to absolute zero. ... The integers consist of the positive natural numbers (1, 2, 3, …), their negatives (−1, −2, −3, ...) and the number zero. ...

As a mathematical consequence, fermions exibit strong repulsion when their wave function overlap, but bosons do not. Fermi repulsion results in stiffness of fermions. That is why atoms (and atomic matter) or neutrons are "stiff" or "rigid" to touch - but bosons are not. Fermions, named after Enrico Fermi, are particles which form totally-antisymmetric composite quantum states. ... Boson (game) Bosons, named after Satyendra Nath Bose, are particles which form totally-symmetric composite quantum states. ...

See also

• Exchange symmetry