## Conservation laws for the nonlinear Schrödinger equation.(English)Zbl 0585.35080

The purpose of the paper is to obtain a method which allows to derive conservation laws of the quantum nonlinear Schrödinger equation $$i \psi_ t=-\psi_{xx}+2c \psi^{†}\psi^ 2$$ where $$\psi$$ is interpreted as a two dimensional quantum field. The heart of the method is the construction of an operator P which intertwines the Laplacian with boundary conditions corresponding to the Hamiltonian $$(\partial /\partial x_{k+1}-\partial /\partial x_ k)F=cF,$$ $$c>0$$ with the Laplacian with Neumann boundary conditions $$(\partial /\partial x_{k+1}-\partial /\partial x_ k)F=0.$$
Of the infinitely many conservation laws the first four are derived explicitly. The fourth one shows a difference to the analogous classical one. The three first conservation laws reproduce an earlier result by H. B. Thacker [Phys. Rev. D 17, 1031 (1978)].
Reviewer: H.Siedentop

### MSC:

 35Q99 Partial differential equations of mathematical physics and other areas of application 81T08 Constructive quantum field theory 35G20 Nonlinear higher-order PDEs
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### References:

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