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Property C and an inverse problem for a hyperbolic equation. (English) Zbl 0729.35147
Summary: Let (*) $u\sb{tt}-\Delta u+q(x,t)u=0$ in $D\times [0,T]$, where $D\subset R\sp 3$ is a bounded domain with a smooth boundary $\partial D$, $T>d$, $d:=diam D$, q(x,t)$\in C([0,T]$, $L\sp{\infty}(D))$. Suppose that for every (**) $u\vert\sb{\partial D}=f(x,t)\in C\sp 1(\partial D\times [0,T])$, the value $u\sb N\vert\sb{\partial D}:=h(s,t)$ is known, where N is the outer normal to $\partial D$, u solves (*) and (**) and satisfies the initial conditions $u=u\sb t=0$ at $t=0$. Then q(x,t) is uniquely determined by the data $\{$ f,h$\}$, $\forall f\in C\sp 1(\partial D\times [0,T])$ in the subset S of $D\times [0,T]$ consisting of the lines which make 45$\circ$ with the t-axis and which meet the planes $t=0$ and $t=T$ outside $\bar D\times [0,T]$, provided that q(x,t) is known outside S.

##### MSC:
 35R30 Inverse problems for PDE 35L20 Second order hyperbolic equations, boundary value problems
##### Keywords:
property C; multidimensional inverse problems; uniqueness
Full Text:
##### References:
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