# Cauchy Problem

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## Cauchy problem

[kō·shē ‚präb·ləm]*m*from the prescribed values of the solution and of its derivatives of order less than

*m*on a given surface.

*The Great Soviet Encyclopedia*(1979). It might be outdated or ideologically biased.

## Cauchy Problem

one of the fundamental problems of the theory of differential equations, first studied systematically by A. Cauchy. It consists in finding a solution *u(x, t*), for *x* = (*x _{i}*, …,

*x*), of a differential equation of the form

_{n}satisfying the initial conditions

where *G*_{0}—the carrier of the initial data—is a region in the hyperplane *t* = *t*_{0} of the space of variables x_{1}, …, x_{n}. When *F* and *f*_{k}, for *k* = 0, …, *m* — 1, are analytic functions of their arguments, then the Cauchy problem (1), (2) always has a unique solution in some region *G* of the space of variables *t, x* containing *G*_{0}. This solution, however, can prove to be unstable (that is, a small change in the initial data can cause a large change in the solution), for example, for cases when equation (1) is elliptic. If equation (1) is not hyperbolic and the initial data are not analytic, then the Cauchy problem (1), (2) can lose meaning.

### REFERENCES

Courant, R., and D. Hilbert.*Metody matematicheskoi fiziki*, vol. 2. Moscow-Leningrad, 1951. (Translated from German.)

Tikhonov, A. N., and A. A. Samarskii.

*Uraveniia matematicheskoi fiziki*, 3rd ed. Moscow, 1966.

A. V. BITSADZE