|  Momentum | 
In General, and Particle Mechanics > s.a. hamiltonian dynamics
  and systems; phase space.
  * Idea: The conserved quantity related
    to spatial translation invariance of a theory (from movimentum).
  * In classical non-relativistic mechanics:
    A particle with velocity v has momentum p = \(m\,{\bf v}\).
  * In special relativistic mechanics:
    A particle with 4-velocity ua
    has 4-momentum pa
    = mua.
  @ General references: Sibelius FP(90) [mechanical and wave-theoretical aspects];
    Crenshaw PLA(05) [electromagnetic, and Fresnel relations];
    Roche EJP(06) [general definition];
    Lee SHPMP(11)
      [examples of momentum non-conservation in classical mechanics].
  @ History: Gillespie AJP(95)apr [why "p"? :-)];
    Graney TPT(13)-a1309 [John Buridan's 14th century concept].
  @ In special relativity:
    Sonego & Pin EJP(05),
    EJP(05);
    Adkins AJP(08)nov;
    Riggs TPT(16) [vs Newtonian dynamics].
  @ Other systems: Liu et al PRA(11) [free particle on a 2-sphere, geometric momentum];
    Exner a1205-fs [on graphs];
    Liu JMP(13)
      [particle on a curved hypersurface].
  > Related topics:
    see conservation laws.
Momentum-Space Geometry
  > s.a. finsler geometry.
  @ General references:
    Freidel & Smolin a1103 [and photon propagation];
    Amelino-Camelia et al CQG(12)-a1107 [distant observers and phenomenology];
    Kowalski-Glikman IJMPA(13)-a1303 [curved, rev];
    Freidel et al IJMPD(14)-a1405-GRF [dynamical momentum space and string theory];
    Lobo & Palmisano IJMPcs(16)-a1612 [isometry group and Planck-scale-deformed co-products].
  @ Curved momentum space and spacetime: Freidel & Rempel a1312 [scalar quantum field theory in curved momentum space];
    Gutierrez-Sagredo et al a1907-conf [non-commutative  spacetimes];
    Lizzi et al NPB(20)-a2001 [for κ-Minkowski spacetime];
    Relancio & Liberati a2002 [cotangent bundle geometry],
    a2008 [constraints].
  @ Relative locality:
    Kowalski-Glikman IJGMP(12)-a1205-proc [and curved momentum space];
    Amelino-Camelia et al a1307;
    Banburski & Freidel PRD(14)-a1308 [non-commutativity related to Snyder spacetime];
    Amelino-Camelia a1408
      [non-linear composition law and the soccer-ball problem];
    > s.a. Fermi Surface.
  @ Phenomenology of curved momentum space:
    Amelino-Camelia et al PLB(16)-a1605,
    a1609 [dual redshift and dual lensing];
    > s.a. modified thermodynamics [photon gas in curved momentum space];
    Carmona et al PRD(19)-a1907,
    a1912 [deformed kinematics].
In Field Theory
  * In general: The momentum
    density of matter Tab as
    seen by an observer ta is
    − tb
    T ab.
  @ For an electromagnetic field:
    Babson et al AJP(09)sep;
    Spavieri & Gillies G&C(10)-a1005 [speed of light in moving media, and photon mass];
    Brevik & Ellingsen AP(11)-a1008,
    comment Griffiths AP(12) [in media];
    Griffiths AJP(12)jan [RL];
    Crenshaw AP(13) [field and matter momentum in a linear dielectric];
    Franklin AJP(14)sep [static electromagnetic fields];
    Corrêa & Saldanha PRA(16)-a1601 [and reflection by a quantum mirror];
    Singal AJP(16)oct;
    Brevik AP(17)-a1610 [Minkowski momentum]; Johns a2105 [and flow of field energy].
  @ Internal electromagnetic momentum and "hidden" momentum:
    Boyer AJP(15)may-a1408,
    PRE(15)-a1408;
    > s.a. magnetism.
  @ For a fluid: Vishwakarma ASS(09)-a0705,
    Jagannathan AJP(09)may [pressure contribution to fluid momentum density].
  > For an electromagnetic field:
    see energy-momentum tensor [including the Abraham-Minkowski dilemma, for light];
    fields in media; maxwell theory.
  > For gravity: see canonical general
    relativity [various formulations]; gravitational energy-momentum.
In Quantum Theory
  > s.a. quantum field theory in generalized
  backgrounds; wigner function.
  * Quantum mechanics:
    A momentum operator conjugate to a configuration variable is one with the
    right commutation relations; If classically the momentum is associated
    to a vector field ua
    on configuration space C, a quantum momentum operator
    can be defined by û ψ(x):=
    i (£u
    + \(1\over2\)div u) ψ(x), where
    the divergence is calculated using the volume element on C
    with respect to which the operator must be self-adjoint.
  * For a wave: A 1-particle
    wave with wave vector k has momentum p
    = ħk, or p = h/λ.
  @ General references: Jordan AJP(75)dec;
    Roy et al RMF-a0706 [in general coordinates];
    Gaveau & Schulman JPA(12)-a1206 [relative momentum of identical particles];
    Berry EJP(13) [five different, equivalent definitions];
    Xiao & Liu a1605 [canonical momentum vs geometric momentum].
  @ Radial momentum: Paz EJP(01)qp/00;
    Mosley mp/03;
    Liu & Xiao a1411. 
  @ Momentum representation:
    Lombardi a1906 [for the hydrogen atom]. 
  @ Non-trivial configuration spaces:
    Shikano & Hosoya JMP(08) [on a half-line];
    Liu et al IJGMP(13)-a1212 [on a 2-sphere, and coherent states].
  @ Maximum momentum: Ching & Ng MPLA(14)-a1311 [effect on wave equations];
    > s.a. deformation quantization;
      deformed uncertainty relations.
  @ Other systems, quantum field theory: de Haan ht/06 [electron mechanical momentum in QED];
    Arzano CQG(14)-a1305 [3D semiclassical gravity with point particles, deformed Fock space];
    Oliveira & Saldanha PRA(15)-a1507 [hidden momentum in a hydrogen atom in an external electric field].
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