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Consider the operator \begin{eqnarray*} K_{n} &:&L^{2}(0,1)\longrightarrow L^{2}(0,1)^{n}, \\ u(x) &\mapsto &A_{n}U_{n}(x)=A_{n}(u(\frac{x}{n}),u(\frac{x+1}{n}),...,u(% \frac{x+n-1}{n}))^{t} \end{eqnarray*}

where $A_{n}$ is $n\times n$ matrix with $\det (A_n)\neq 0,$ $\forall n\geq 1.$

It is clear that $K_{n}$ is onto since for any $Y\in L^{2}(0,1)^{n}$ the equation $A_nU_n(x)=Y(x)$ admits a unique solution in $L^{2}(0,1)^{n}$which makes $u$ uniquely determined in this case.

I'm wondering about the surjectivity property for $n\mapsto \infty .$ If we assume that $\underset{n\longrightarrow \infty }{\lim }\det (A_n)\neq 0$ do we obtain that the limit operator $K_{\infty }$ is surjective?.

I was thinking of studying the adjoint $K_{n}^{\ast \text{ }}$ and proving that $K_{n}^{\ast \text{ }}v_{n}=0$ for some $\left\Vert v_{n}\right\Vert _{L^{2}(0,1)^{n}}=1$ but I didn't succeed. Any ideas?. Thank you in advance?

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    $\begingroup$ What is your limit operator? Also, the limit in what sense? $\endgroup$ Commented Jul 15, 2021 at 14:13
  • $\begingroup$ thank you sir for the answer. I can treat the surjectivity problem pointwisely ( for instance u is continuous). I worked in L2 because of the adjoint. $\endgroup$
    – Gustave
    Commented Jul 15, 2021 at 14:18
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    $\begingroup$ In what sense does $A_n$ have a limit? $\endgroup$ Commented Jul 15, 2021 at 16:03
  • $\begingroup$ Thank you sir for the answer. In the $L^2$ sense sir. $\endgroup$
    – Gustave
    Commented Jul 15, 2021 at 16:04

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