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. To suggest a relevant news story for the main page, refer to the criteria then add your suggestion at the candidates page. ... 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. ...

According to quantum mechanics or quantum field theory, particles of the same type are indistinguishable and thus mathematically behave either as bosons or fermions. In the former case, two (or more) particles can occupy the same quantum state and this fact may be vaguely interpreted as an attractive exchange force; in the latter case, the particles can not occupy the same state (the Pauli exclusion principle)) - this effect may be interpreted as a repulsive exchange force (or exchange pressure). A simple introduction to this subject is provided in Basics of quantum mechanics. ... Quantum field theory (QFT) is the application of quantum mechanics to fields. ... In physics, bosons, named after Satyendra Nath Bose, are particles with integer spin. ... In particle physics, fermions, (named after Enrico Fermi), are particles with semi-integer spin. ... A quantum state is any possible state in which a quantum mechanical system can be. ... 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. ...

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. Where wave functions of electrons overlap Pauli repulsion takes place. Same is true for protons and neutrons (due to large mass rigidness of barions is much larger than of electrons). In contrast, overlaping of wave function of bosons does not result in repulsion - thus bosons are not "rigid". 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. ... In the most restricted usage in quantum mechanics, the wavefunction associated with a particle such as an electron, is a complex-valued square integrable function ψ defined over a portion of space and normalized in such a way that In Max Borns probabilistic interpretation of the wavefunction, the amplitude squared... For alternative meanings see proton (disambiguation). ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ...

Interesting that actual fundamental forces are not forces per se, but results of conservation of momentum during exchange by virtual bosons called force carriers. Due to this fact more accurate term fundamental interactions is used instead of older term "fundamental forces". A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... The virtual is a concept applied in many fields with somewhat differing connotations, and also denotations. ... In physics, bosons, named after Satyendra Nath Bose, are particles with integer spin. ... In particle physics, the quantum field theory called the Standard Model describes the strong, weak and electromagnetic fundamental forces. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ...

See also

• Exchange symmetry