A nonlinear version of Ovcyannikov’s theorem is proved. If F ( u , t ) F(u,t) is an analytic function of t t real or complex and of u u varying in a scale of Banach spaces, valued in a scale of Banach spaces, the Cauchy problem u t = F ( u , t ) , u ( 0 ) = u 0 {u_t} = F(u,t),u(0) = {u_0} , has a unique analytic solution. This is an abstract version of the Cauchy-Kovalevska theorem which can be applied to equations other than partial-differential, e.g. to certain differential-convolution or, more generally, differential-pseudodifferential equations.
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