Extended Global Approximation Theorem in Sobolev Space











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In Evans,




$textbf{Theorem} $ (Global Approximation Theorem) Assume $U$ is bounded, and $partial U$ is $C^1$. Suppose as well that $u in W^{k,p}(U)$ for some $1leq p < infty$. Then, there exist functions $u_m in C^{infty}(bar{U})$ such that
begin{align*}
u_m rightarrow u quad textrm{ in } W^{k,p}(U)
end{align*}




$textbf{Question}$ Although we change the boundary condition like
begin{align*}
partial U=bigcup_{j=1}^n Gamma_j, quad (textrm{boundary is piecewise } C^{1})
end{align*}

where each $Gamma_j$ for $j=1, cdots, n$ is a $C^1$, $Gamma_j$ and $Gamma_{j^{'}}$ do not intersect except at their endpoints if $jneq j'$, then does the theorem still hold?



Any help is appreciated!!



I want to know references related that...



Thank you!!










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    up vote
    1
    down vote

    favorite












    In Evans,




    $textbf{Theorem} $ (Global Approximation Theorem) Assume $U$ is bounded, and $partial U$ is $C^1$. Suppose as well that $u in W^{k,p}(U)$ for some $1leq p < infty$. Then, there exist functions $u_m in C^{infty}(bar{U})$ such that
    begin{align*}
    u_m rightarrow u quad textrm{ in } W^{k,p}(U)
    end{align*}




    $textbf{Question}$ Although we change the boundary condition like
    begin{align*}
    partial U=bigcup_{j=1}^n Gamma_j, quad (textrm{boundary is piecewise } C^{1})
    end{align*}

    where each $Gamma_j$ for $j=1, cdots, n$ is a $C^1$, $Gamma_j$ and $Gamma_{j^{'}}$ do not intersect except at their endpoints if $jneq j'$, then does the theorem still hold?



    Any help is appreciated!!



    I want to know references related that...



    Thank you!!










    share|cite|improve this question


























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      In Evans,




      $textbf{Theorem} $ (Global Approximation Theorem) Assume $U$ is bounded, and $partial U$ is $C^1$. Suppose as well that $u in W^{k,p}(U)$ for some $1leq p < infty$. Then, there exist functions $u_m in C^{infty}(bar{U})$ such that
      begin{align*}
      u_m rightarrow u quad textrm{ in } W^{k,p}(U)
      end{align*}




      $textbf{Question}$ Although we change the boundary condition like
      begin{align*}
      partial U=bigcup_{j=1}^n Gamma_j, quad (textrm{boundary is piecewise } C^{1})
      end{align*}

      where each $Gamma_j$ for $j=1, cdots, n$ is a $C^1$, $Gamma_j$ and $Gamma_{j^{'}}$ do not intersect except at their endpoints if $jneq j'$, then does the theorem still hold?



      Any help is appreciated!!



      I want to know references related that...



      Thank you!!










      share|cite|improve this question















      In Evans,




      $textbf{Theorem} $ (Global Approximation Theorem) Assume $U$ is bounded, and $partial U$ is $C^1$. Suppose as well that $u in W^{k,p}(U)$ for some $1leq p < infty$. Then, there exist functions $u_m in C^{infty}(bar{U})$ such that
      begin{align*}
      u_m rightarrow u quad textrm{ in } W^{k,p}(U)
      end{align*}




      $textbf{Question}$ Although we change the boundary condition like
      begin{align*}
      partial U=bigcup_{j=1}^n Gamma_j, quad (textrm{boundary is piecewise } C^{1})
      end{align*}

      where each $Gamma_j$ for $j=1, cdots, n$ is a $C^1$, $Gamma_j$ and $Gamma_{j^{'}}$ do not intersect except at their endpoints if $jneq j'$, then does the theorem still hold?



      Any help is appreciated!!



      I want to know references related that...



      Thank you!!







      analysis pde sobolev-spaces






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      edited 6 hours ago

























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      w.sdka

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