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Maximum Principles and Energy Methods

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Essential Partial Differential Equations

Abstract

This chapter extends the ideas in earlier chapters and identifies two concepts that are useful for checking the well-posedness of boundary value problems. These concepts play a fundamental role in establishing the stability of finite difference solutions in later chapters.

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Notes

  1. 1.

    The alternative norm \(\Vert \mathscr {F}\Vert =\max _{(x,t)\in {\varOmega _{\tau }}}|f(x,t)|+\max _{(x,t)\in \varGamma _{\!\tau }}|g(x,t)|\) leads to a slightly larger upper bound.

  2. 2.

    This might occur, for instance, when u is the pressure in a fluid. In such systems it is usually only the difference in pressure between two points and not the absolute pressure that can be measured.

  3. 3.

    The PDE may be written in the form of a conservation law \(u_{t}+f(u)_{x}=0\) with a flux function \(f(u) = 2u-u_{x}\). The boundary conditions are then seen to be zero-flux conditions.

  4. 4.

    An indication of the special nature of the KdV equation is that it has an infinite number of such conserved quantities.

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Correspondence to David F. Griffiths .

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© 2015 Springer International Publishing Switzerland

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Griffiths, D.F., Dold, J.W., Silvester, D.J. (2015). Maximum Principles and Energy Methods. In: Essential Partial Differential Equations. Springer Undergraduate Mathematics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-22569-2_7

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