# Free Particle

In physics, a free particle is a particle that, in some sense, is not bound by an external force, or equivalently not in a region where its potential energy varies. In classical physics, this means the particle is present in a "field-free" space. In quantum mechanics, it means a region of constant potential, usually set to zero in the region of interest since potential can be arbitrarily set to zero at any point (or surface in three dimensions) in space.

### Other articles related to "free particle, particle":

Path Integral Formulation - Concrete Formulation - The Schrödinger Equation
... The second term is the free particle propagator, corresponding to i times a diffusion process ... in any case one has with (1) As mentioned, the spread in ψ is diffusive from the free particle propagation, with an extra infinitesimal rotation in phase which slowly varies from point to point from ... needs to be fixed in exactly the same way as in the free particle case ...
Gross–Pitaevskii Equation - Solutions - Exact Solutions - Free Particle
... The simplest exact solution is the free particle solution, with , This solution is often called the Hartree solution ...
Relativistic Free Particle
... There are a number of equations describing relativistic particles see relativistic wave equations. ...
Crystal Momentum - Physical Significance
... The phase modulation of the Bloch state is the same as that of a free particle with momentum, i.e ... This modulation contributes to the kinetic energy of the particle (whereas the modulation is entirely responsible for the kinetic energy of a free particle) ... the band is approximately parabolic the crystal momentum is equal to the momentum of a free particle with momentum if we assign the particle an effective mass that's related to the curvature of the parabola ...
Hamiltonian (quantum Mechanics) - Energy Eigenket Degeneracy, Symmetry, and Conservation Laws
... A simple example of this is a free particle, whose energy eigenstates have wavefunctions that are propagating plane waves ... In the case of the free particle, the unitary operator which produces the symmetry is the rotation operator, which rotates the wavefunctions by some angle while otherwise preserving their shape ... In the case of the free particle, the conserved quantity is the angular momentum ...

### Famous quotes containing the words particle and/or free:

Each particle is a microcosm, and faithfully renders the likeness of the world.
Ralph Waldo Emerson (1803–1882)

The proposition that Muslims are welcome in Britain if, and only if, they stop behaving like Muslims is a doctrine which is incompatible with the principles that guide a free society.
Roy Hattersley (b. 1932)