Conservation Laws, Conserved Quantities  

In General > s.a. asymptotic flatness at spatial and null infinity; differential equations; lagrangian dynamics.
* Applications: They are useful for studying the evolution of a system without knowing details about the motion, to give a classification of all possible evolutions, etc, and to reduce the order of the differential equations describing the motion.

From Symmetries > s.a. Noether Symmetries; killing fields; symmetries.
* Idea: Generators of symmetries give rise to conserved currents, whose integrals are conserved quantities.
* Superpotential: An (n–2)-form () in an n-dimensional spacetime, associated with an infinitesimal Lagrangian symmetry , such that the boundary term in the conserved quantity Q() = Qbulk() + Qbdry() is

Qbdry() = bdry(Sigma) () ;

The term also denotes a potential for a stress-energy pseudotensor, mn = a m[na].
@ General references: Katzin JMP(73) [quadratic constants of the motion]; Rosen & Freundlich AJP(78) [general framework]; Norbury EJP(88) [pedagogical, for momentum]; Schulte SHPMP(08) [and particle families]; Smith SHPMP(08) [in Lagrangian mechanics]; Ivanova et al a0806.
@ Non-Noether symmetries: Hojman JPA(92) + González-Gascón JPA(94) + Lutzky JPA(95); Anco & Bluman PRL(97) [for field theories]; Kara & Mahomed IJTP(00); Chavchanidze mp/02, JGP(03)mp/02; > s.a. lagrangian dynamics.
@ Related topics: Kara et al IJTP(99) [approximate symmetries]; in Francaviglia & Raiteri CQG(02)gq/01 [superpotential].

Related Concepts > s.a. Chevreton Tensor; energy; observables; stress-energy pseudotensor; superselection rules.
* Continuity equation: A local, differential form of conservation equation; If u is a velocity/flow 4-vector and f a source strength, then

a ua = f ,   or   ,t + · (v) = f   in 3+1 form .

@ General references: Horwood JMP(07) [higher-order first integrals].
@ Energy-momentum conservation: Giachetta et al G&C(99) [gauge approach]; > s.a. energy-momentum.
@ Time-dependent invariants of motion: Sarris & Proto PhyA(05) [complete sets of non-commuting observables].
@ Center of energy: Boyer AJP(05) [illustrations].

Specific Theories > s.a. electromagnetism; energy; energy-momentum; hamiltonian systems.
* In Newtonian theory: Only 4 were known at the end of the XIX cy, mass, linear momentum, angular momentum (these are multipole moments), and energy.
* In relativistic theory: Expressed by T ab;b = 0; If the spacetime has a Killing vector field a, then T ab b is a conserved current.
@ Gauge theories: Chodos CMP(79) [Yang-Mills theory]; Przeszowski JPA(89) [non-abelian currents]; Gauge & Henneaux MPLA(95)ht [abelian and non-abelian currents]; Barnich et al LMP(04)gq [n–2 forms in curved spacetime, classification].
@ Spinor fields: Anco & Pohjanpelto PRS(03)mp/02 [any spin].
@ Gravity: Wald & Zoupas PRD(00)gq/99; Papadopoulos JMP(06)gq/05 [essential constants]; Obukhov & Rubilar PRD(06)gq, PRD(07)-a0712, PLB(08)-a0712; Alves et al a0710-GRG [in massive graviton theory]; > s.a. gravitational action, quasilocal energy.
@ Particle dynamics: Katzin & Levine JMP(74); Cetto & de la Peña AJP(84) [relationship between energy and adiabatic invariant J]; Hojman et al JMP(86), Del Castillo & Hojman JMP(90) [geodesic motion]; > s.a. diffusion.

References > s.a. Superposition Principle.
@ General: Takens 77; Uhlenbeck in(83); Amigo & Reeh FdP(88) [additive constants of motion]; Serre 00; Jiang & Li IJTP(07) [classical vs quantum].
@ Related topics: Olszewski AJP(83) [non-conservation of E, p, L in non-static spacetime]; Sidharth CSF(00)qp/98 [statistical view].


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