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Cauchy problem

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ACauchy problem in mathematics asks for the solution of apartial differential equation that satisfies certain conditions that are given on ahypersurface in the domain.[1] A Cauchy problem can be aninitial value problem or aboundary value problem (for this case see alsoCauchy boundary condition). It is named afterAugustin-Louis Cauchy.

Formal statement

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For a partial differential equation defined onRn+1 and asmooth manifoldSRn+1 of dimensionn (S is called theCauchy surface), the Cauchy problem consists of finding the unknown functionsu1,,uN{\displaystyle u_{1},\dots ,u_{N}} of the differential equation with respect to the independent variablest,x1,,xn{\displaystyle t,x_{1},\dots ,x_{n}} that satisfies[2]niuitni=Fi(t,x1,,xn,u1,,uN,,kujtk0x1k1xnkn,)for i,j=1,2,,N;k0+k1++kn=knj;k0<nj{\displaystyle {\begin{aligned}&{\frac {\partial ^{n_{i}}u_{i}}{\partial t^{n_{i}}}}=F_{i}\left(t,x_{1},\dots ,x_{n},u_{1},\dots ,u_{N},\dots ,{\frac {\partial ^{k}u_{j}}{\partial t^{k_{0}}\partial x_{1}^{k_{1}}\dots \partial x_{n}^{k_{n}}}},\dots \right)\\&{\text{for }}i,j=1,2,\dots ,N;\,k_{0}+k_{1}+\dots +k_{n}=k\leq n_{j};\,k_{0}<n_{j}\end{aligned}}}subject to the condition, for some valuet=t0{\displaystyle t=t_{0}},

kuitk=ϕi(k)(x1,,xn)for k=0,1,2,,ni1{\displaystyle {\frac {\partial ^{k}u_{i}}{\partial t^{k}}}=\phi _{i}^{(k)}(x_{1},\dots ,x_{n})\quad {\text{for }}k=0,1,2,\dots ,n_{i}-1}

whereϕi(k)(x1,,xn){\displaystyle \phi _{i}^{(k)}(x_{1},\dots ,x_{n})} are given functions defined on the surfaceS{\displaystyle S} (collectively known as theCauchy data of the problem). The derivative of order zero means that the function itself is specified.

Cauchy–Kowalevski theorem

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TheCauchy–Kowalevski theorem states thatIf all the functionsFi{\displaystyle F_{i}} areanalytic in some neighborhood of the point(t0,x10,x20,,ϕj,k0,k1,,kn0,){\displaystyle (t^{0},x_{1}^{0},x_{2}^{0},\dots ,\phi _{j,k_{0},k_{1},\dots ,k_{n}}^{0},\dots )}, and if all the functionsϕj(k){\displaystyle \phi _{j}^{(k)}} are analytic in some neighborhood of the point(x10,x20,,xn0){\displaystyle (x_{1}^{0},x_{2}^{0},\dots ,x_{n}^{0})}, then the Cauchy problem has a unique analytic solution in some neighborhood of the point(t0,x10,x20,,xn0){\displaystyle (t^{0},x_{1}^{0},x_{2}^{0},\dots ,x_{n}^{0})}.

See also

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References

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  1. ^Hadamard, Jacques (1923).Lectures on Cauchy's Problem in Linear Partial Differential Equations. New Haven: Yale University Press. pp. 4–5.OCLC 1880147.
  2. ^Petrovsky, I. G. (1991) [1954].Lectures on Partial Differential Equations. Translated by Shenitzer, A. (Dover ed.). New York: Interscience.ISBN 0-486-66902-5.

Further reading

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  • Hille, Einar (1956)[1954]. Some Aspect of Cauchy's Problem Proceedings of 1954 ICM vol III section II (analysis half-hour invited address) p. 1 0 9 ~ 1 6.
  • Sigeru Mizohata(溝畑 茂 1965). Lectures on Cauchy Problem. Tata Institute of Fundamental Research.
  • Sigeru Mizohata (1985).On the Cauchy Problem. Notes and Reports in Mathematics in Science and Engineering. 3. Academic Press, Inc.. ISBN 9781483269061
  • Arendt, Wolfgang; Batty, Charles; Hieber, Matthias; Neubrander, Frank (2001), Vector-valued Laplace Transforms and Cauchy Problems, Birkhauser.

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