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In physics, Liouville's theorem, named after the French mathematician Joseph Liouville, is a key theorem in classical statistical and Hamiltonian mechanics.It asserts that the phase-space distribution function is constant along the trajectories of the system—that is that the density of system points in the vicinity of a given system point traveling through phase-space is constant with time.
Liouville's equation can be used to prove the following classification results for surfaces: 7] A surface in the Euclidean 3-space with metric dl 2 = g(z, _)dzd _, and with constant scalar curvature K is locally isometric to: the sphere if K > 0; the Euclidean plane if K = 0; the Lobachevskian plane if K < 0.
The quantum Liouville equation is the Weyl–Wigner transform of the von Neumann evolution equation for the density matrix in the Schrödinger representation. The quantum Hamilton equations are the Weyl–Wigner transforms of the evolution equations for operators of the canonical coordinates and momenta in the Heisenberg representation.
In differential algebra, see Liouville's theorem (differential algebra) In differential geometry, see Liouville's equation; In coarse-grained modelling, see Liouville's equation in coarse graining phase space in classical physics and fine graining of states in quantum physics (von Neumann density matrix)
Dynamics of the probability density (proof) In classical statistical mechanics, the probability density (with respect to Liouville measure) obeys the Liouville equation [4] [5] (,,) = ^ (,,) with the self-adjoint Liouvillian ^ = (,) + (,), where (,) denotes the classical Hamiltonian (i.e. the Liouvillian is times the Hamiltonian vector field considered as a first order differential operator).
Such constants of motion will commute with the Hamiltonian under the Poisson bracket. Suppose some function f ( p , q ) {\displaystyle f(p,q)} is a constant of motion. This implies that if p ( t ) , q ( t ) {\displaystyle p(t),q(t)} is a trajectory or solution to Hamilton's equations of motion , then 0 = d f d t {\displaystyle 0={\frac {df}{dt ...
In physics, Liouville field theory (or simply Liouville theory) is a two-dimensional conformal field theory whose classical equation of motion is a generalization of Liouville's equation. Liouville theory is defined for all complex values of the central charge c {\displaystyle c} of its Virasoro symmetry algebra , but it is unitary only if
Hamilton's equations give the time evolution of coordinates and conjugate momenta in four first-order differential equations, ˙ = ˙ = ˙ = ˙ = Momentum , which corresponds to the vertical component of angular momentum = ˙ , is a constant of motion. That is a consequence of the rotational symmetry of the ...