|  Variational Principles in Physics | 
In General > s.a. Variational Principles
  / jacobi dynamics; Maupertuis Principle.
  * Idea: The equations of motion and/or
    other equations of interest are given by imposing δS = 0; The restrictions
    chosen on the variations δq determine the type of variational principle;
    Least action: Minimize ∫ p · dl, with
    x1 and x2 fixed.
  * Hamilton's principle:
    (δS)t
    = 0, the usual one, where one fixes t and q at
    the endpoints of the trajectories; The vanishing of δS
    then gives the Euler-Lagrange equations of motion; Reciprocal:
    (δt)S = 0;
    Unconstrained: δS = −E δt.
  * Jacobi principle: Fix the
    energy E and find the path by extremizing the Jacobi action
S = ∫ dx {2m[E−V(x)]}1/2
    with respect to paths x(s) in configuration space; Time
    dependence is recovered only after imposing another, metric condition.
  * Maupertuis principle:
    (δW)E = 0;
    Generalized: (δW)E' = 0;
    Reciprocal: (δE')W = 0;
    Unconstrained: δW = t δE'.
  * Weiss principle: The
    endpoints of trajectories are not held fixed; It yields the canonical momenta.
References
  > s.a. classical and quantum mechanics [unified description];
    lagrangian dynamics.
  @ Texts: Lanczos 49;
    Weinstock 52;
    in Goldstein 80;
    Kuperschmidt 92;
    Lemons 97;
    Basdevant 07.
  @ General references:
    in Brown & York PRD(89);
    Gray et al AP(96);
    Tulczyjew mp/04 [origin = virtual work];
    Hanc et al AJP(05)jul [use of Maupertuis, 1D and 2D];
    Gondran & Gondran a1212
      ["final causes" vs "efficient causes" and Euler-Lagrange vs Hamilton-Jacobi action];
    Bekenstein & Majhi NPB(15)-a1411 [field equations from the action without variation];
    Anderson et al AJP(16)sep [direct variational methods
      and their relation to Galerkin and moment methods, intro].
  @ Conceptual:
    Wang a0808 [philosophical, dialectical view];
    Terekhovich a1909-in [ontology].
  @ Calculus of variations: de Donder 35;
    Hermann 68; Goldstine 80 [history];
    Struwe 90;
    Blanchard & Bruning 92;
    Giusti 03 [direct methods];
    Chang 16 [lecture notes].
  @ Non-differentiable versions: 
    Luo et al CTP(04)mp [including symplectic];
    Almeida & Torres MMAS(11)-a1106 [Cresson approach, on the space of Hölder functions].
  @ Higher-order calculus of variations:
    Francaviglia et al DG&A(05);
    > s.a. higher-order lagrangians.
  @ Hamilton's principle:
    Bażański & Jaranowski JPA(94) [vs Jacobi];
    Wharton a0906/PRL [re quantization];
    Kapsa & Skála JPA(09) [from spacetime Fisher information].
  @ Other principles: Romano et al RPMP(09) [Maupertuis, new formulation and time-dependent systems];
    Feng & Matzner GRG(18) [Weiss, and gravity].
  @ With given initial position and velocity: Galley PRL(13)-a1210
      [and application to the Lagrangian and Hamiltonian dynamics of non-conservative systems];
    Gondran & Gondran a1210-proc [and quantum theory].
  @ Invariant derivation of equations of motion:
    Nester JPA(88).
  @ Inverse problem: Marmo et al CQG(90) [metric from test-particle motion];
    Ercolessi et al RNC(10)-a1005 [and quantum commutation relations];
    Saunders RPMP(10) [rev];
    > s.a. discrete systems below.
  @ Related topics:
    Kaup & Lakoba JMP(96) [caveat re instabilities];
    Nishimura IJTP(99) [infinitesimal form].
Types of Systems and Generalizations > s.a. constrained systems
  and types [non-holonomic]; schrödinger
  equation; Schwinger's Principle.
  @ General references: Ichiyanagi PRP(94) [irreversible processes];
    Núñez-Yépez & Salas-Brito PLA(00)mp [Jacobi equations];
    Pankrashkin a0710
      [Hamiltonians with degenerate lowest-energy states];
    Esteban et al BAMS(08) [in relativistic quantum mechanics];
    > s.a. conservation laws [theories with symmetries].
  @ For stochastic processes:
    Yasue JFA(81);
    Koide & Kodama JPA(12)-a1105 [and the Navier-Stokes equation];
    > s.a. stochastic quantization.
  @ For non-conservative systems:
    Galley et al a1412 [stationary action].
  @ For field theories: Vankerschaver et al JMP(12)-a1207 [Hamilton-Pontryagin principle and multi-Dirac structures];
    Siringo PRD(14)-a1308,
    MPLA(14)-a1308 [principle of stationary variance in quantum field theory];
    Bäckdahl & Valiente Kroon JMP(16)-a1505 [with spinors].
  @ Discrete systems: Dittrich & Höhn JMP(13)-a1303 [constraint analysis];
    Gubbiotti a1808 [inverse problem].
  @ Fractional variational principles: 
    El-Nabulsi & Torres JMP(08);
    Baleanu RPMP(08);
    Almeida & Torres AML(09)-a0907;
    Malinowska & Torres 13 [intro];
    Odzijewicz et al C&C-a1304 [generalized].
  @ Causal variational principles: Finster JRAM(10)-a0811;
    Finster & Schiefeneder ARMA(13)-a1012;
    Finster et al in(12)-a1102;
    Finster & Grotz JRAM(14)-a1303;
    Finster & Kleiner CVPDE(17)-a1612 [Hamiltonian formulations];
    > s.a. Initial-Value Problem.
  > Specific types of systems:
    see action for general relativity; dissipative
    systems; types of lagrangian systems.
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