In General > s.a. G-parity; Isospin; noether charge; topology in physics [topological charges].
* Idea: Loosely speaking, a charge is a conserved quantity other than energy-momentum.
* And conserved currents: When a charge is conserved because it is associated with a conserved current, it can be calculated as a surface integral (see examples below); > s.a. conservation laws.
> Online resources: see Wikipedia page.

In a Gauge Theory > s.a. electromagnetism; gauge theory.
* Abelian electric charge: The electric charge of an isolated system is

Q = \(1\over2\)\(\displaystyle\oint_S\) Fab dsab = \(\displaystyle\oint_S\) F 0b dsb = \(\displaystyle\oint_S\) Ea dsa ,

where S is any closed (N−1)-surface in N+1 spacetime dimensions enclosing the system, possibly a surface at infinity, S.
* Non-abelian theory: The electric and magnetic charges Q and F have internal indices; For a Yang-Mills theory they are, respectively,

Q ij = \(1\over4\pi\)\(\displaystyle\oint_S\) Eaij dsa   and  P = \(1\over2\)\(\displaystyle\oint_S\) *Fab dsab = \(\displaystyle\oint_S\) Ba dsa ;

Several electric and magnetic charges can actually be defined; 'Brane source charge' is gauge invariant and localized but not conserved or quantized, 'Maxwell charge' is gauge invariant and conserved but not localized or quantized, while 'Page charge' conserved, localized, and quantized but not gauge invariant [@ Marolf ht/00-proc].
@ Abelian, electric charge: Segers et al AJP(09)jan [Einstein's "little machine" to measure small charges]; Dzhunushaliev a1002 [non-perturbative, finite quantum field theory corrections]; Gratus et al FP(19)-a1904 [on possible non-conservation].
@ General references: Sniatycky & Schwartz RPMP(94) [no local non-abelian charge density]; Marolf ht/00-proc; Lyre IJMPD(00)gq [equivalence principle for charge]; Barnich CQG(03)ht [boundary charges]; McMullan Sigma(07)ht; > s.a. topology in physics.

Specific Systems and Particles > s.a. electron [decay]; particle types.
@ In gravity: Hollands et al PRD(05)ht/05 [counter-term subtraction definition]; Bousso et al PRD(18)-a1709 [asymptotic charges cannot be observed in finite retarded time]; > s.a. anti-de sitter space; gravitational energy.

References > s.a. renormalization.
@ General: Klauder & Wheeler RMP(57) [re neutrinos]; Toussaint GRG(00)gq/99 [general relativity / gauge theory]; Hofer qp/00 [origin?].
@ Quantization: Rosen IJTP(79); Staruszkiewicz AP(89); Rañada & Trueba PLB(98)ht [topological]; Rañada ht/99; Olive ht/01-conf; Allen et al ht/02; Pérez-Lorenzana & Pires MPLA(03) [higher dimensions]; Barone & Helayël-Neto qp/04-proc, comment MacKenzie et al qp/05 [and Aharonov-Bohm effect]; Minguzzi et al JPA(06) [from weak gauge principle]; Buitrago a1404 [from 2-spinor approach to U(1) gauge theory]; Solha JGP(16)-a1409 [topological argument, without magnetic monopoles]; > s.a. experiments in physics; kaluza-klein theory; monopoles [Dirac's argument].
@ Fractional charges: Wilczek cm/02-in; Gies et al PRL(06) [unquantized 'millicharged fermions', search]; > s.a. Hall Effect [fractional]; Quarks; types of dark matter.

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