The main goal of this paper is to derive an alternative characterization of the multisymplectic form formula for classical field theories using the geometry of the space of boundary values. We review the concept of Type-I/II generating functionals defined on the space of boundary data of a Lagrangian field theory. On the Lagrangian side, we define an analogue of Jacobi's solution to the Hamilton–Jacobi equation for field theories, and we show that by taking variational derivatives of this functional, we obtain an isotropic submanifold of the space of Cauchy data, described by the so-called multisymplectic form formula. As an example of the latter, we show that Lorentz's reciprocity principle in electromagnetism is a particular instance of the multisymplectic form formula. We also define a Hamiltonian analogue of Jacobi's solution, and we show that this functional is a Type-II generating functional. We finish the paper by defining a similar framework of generating functions for discrete field theories, and we show that for the linear wave equation, we recover the multisymplectic conservation law of Bridges.
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August 2013
Research Article|
August 14 2013
Generating functionals and Lagrangian partial differential equations
Joris Vankerschaver;
Joris Vankerschaver
a)
Department of Mathematics,
University of California
, San Diego, 9500 Gilman Drive, Dept. 0112, La Jolla, California 92093-0112, USA
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Cuicui Liao;
Cuicui Liao
b)
Department of Mathematics,
University of California
, San Diego, 9500 Gilman Drive, Dept. 0112, La Jolla, California 92093-0112, USA
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Melvin Leok
Melvin Leok
c)
Department of Mathematics,
University of California
, San Diego, 9500 Gilman Drive, Dept. 0112, La Jolla, California 92093-0112, USA
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a)
Present address: Imperial College London, London SW7 2AZ, United Kingdom. Electronic mail: Joris.Vankerschaver@gmail.com.
b)
Present address: Department of Mathematics, Jiangnan University, No. 1800 Lihu Avenue, Wuxi, Jiangsu 214122, China. Electronic mail: liaocuicuilcc@gmail.com.
c)
Electronic mail: mleok@math.ucsd.edu
J. Math. Phys. 54, 082901 (2013)
Article history
Received:
January 08 2013
Accepted:
July 18 2013
Citation
Joris Vankerschaver, Cuicui Liao, Melvin Leok; Generating functionals and Lagrangian partial differential equations. J. Math. Phys. 1 August 2013; 54 (8): 082901. https://doi.org/10.1063/1.4817391
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