Mixed multidimensional integral equation












0












$begingroup$


1) Suppose
$$
sum_{alphasubset{1,...,N}}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}).
$$

Find $u({bf x})$, i.e. express it in terms of $f({bf x})$.



If $N=1$ then we have
$$
u(x_1)+int_0^1u(x_1)dx_1=f(x_1) Rightarrow u(x_1)=f(x_1)-frac12int_0^1f(x_1)dx_1.
$$



If $N=2$ then
$$
u(x_1,x_2)+int_0^1u(x_1,x_2)dx_1+int_0^1u(x_1,x_2)dx_2+int_0^1int_0^1u(x_1,x_2)dx_1dx_2=f(x_1,x_2)
$$

yields
$$
u(x_1,x_2)=f(x_1,x_2)-frac12int_0^1f(x_1,x_2)dx_1-frac12int_0^1f(x_1,x_2)dx_2+frac14int_0^1int_0^1f(x_1,x_2)dx_1dx_2.
$$



What happens in the case $N>2$?



2) What are the solution and the criteria of invertibility in the general case
$$
sum_{alphasubset{1,...,N}}A_{alpha}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}),
$$

where $A_{alpha}$ are constant numbers?










share|cite|improve this question











$endgroup$

















    0












    $begingroup$


    1) Suppose
    $$
    sum_{alphasubset{1,...,N}}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}).
    $$

    Find $u({bf x})$, i.e. express it in terms of $f({bf x})$.



    If $N=1$ then we have
    $$
    u(x_1)+int_0^1u(x_1)dx_1=f(x_1) Rightarrow u(x_1)=f(x_1)-frac12int_0^1f(x_1)dx_1.
    $$



    If $N=2$ then
    $$
    u(x_1,x_2)+int_0^1u(x_1,x_2)dx_1+int_0^1u(x_1,x_2)dx_2+int_0^1int_0^1u(x_1,x_2)dx_1dx_2=f(x_1,x_2)
    $$

    yields
    $$
    u(x_1,x_2)=f(x_1,x_2)-frac12int_0^1f(x_1,x_2)dx_1-frac12int_0^1f(x_1,x_2)dx_2+frac14int_0^1int_0^1f(x_1,x_2)dx_1dx_2.
    $$



    What happens in the case $N>2$?



    2) What are the solution and the criteria of invertibility in the general case
    $$
    sum_{alphasubset{1,...,N}}A_{alpha}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}),
    $$

    where $A_{alpha}$ are constant numbers?










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      1) Suppose
      $$
      sum_{alphasubset{1,...,N}}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}).
      $$

      Find $u({bf x})$, i.e. express it in terms of $f({bf x})$.



      If $N=1$ then we have
      $$
      u(x_1)+int_0^1u(x_1)dx_1=f(x_1) Rightarrow u(x_1)=f(x_1)-frac12int_0^1f(x_1)dx_1.
      $$



      If $N=2$ then
      $$
      u(x_1,x_2)+int_0^1u(x_1,x_2)dx_1+int_0^1u(x_1,x_2)dx_2+int_0^1int_0^1u(x_1,x_2)dx_1dx_2=f(x_1,x_2)
      $$

      yields
      $$
      u(x_1,x_2)=f(x_1,x_2)-frac12int_0^1f(x_1,x_2)dx_1-frac12int_0^1f(x_1,x_2)dx_2+frac14int_0^1int_0^1f(x_1,x_2)dx_1dx_2.
      $$



      What happens in the case $N>2$?



      2) What are the solution and the criteria of invertibility in the general case
      $$
      sum_{alphasubset{1,...,N}}A_{alpha}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}),
      $$

      where $A_{alpha}$ are constant numbers?










      share|cite|improve this question











      $endgroup$




      1) Suppose
      $$
      sum_{alphasubset{1,...,N}}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}).
      $$

      Find $u({bf x})$, i.e. express it in terms of $f({bf x})$.



      If $N=1$ then we have
      $$
      u(x_1)+int_0^1u(x_1)dx_1=f(x_1) Rightarrow u(x_1)=f(x_1)-frac12int_0^1f(x_1)dx_1.
      $$



      If $N=2$ then
      $$
      u(x_1,x_2)+int_0^1u(x_1,x_2)dx_1+int_0^1u(x_1,x_2)dx_2+int_0^1int_0^1u(x_1,x_2)dx_1dx_2=f(x_1,x_2)
      $$

      yields
      $$
      u(x_1,x_2)=f(x_1,x_2)-frac12int_0^1f(x_1,x_2)dx_1-frac12int_0^1f(x_1,x_2)dx_2+frac14int_0^1int_0^1f(x_1,x_2)dx_1dx_2.
      $$



      What happens in the case $N>2$?



      2) What are the solution and the criteria of invertibility in the general case
      $$
      sum_{alphasubset{1,...,N}}A_{alpha}int_{[0,1)^{|alpha|}}u({bf x})d{bf x}_{alpha}=f({bf x}),
      $$

      where $A_{alpha}$ are constant numbers?







      integration






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Dec 6 '18 at 22:12







      AAK

















      asked Dec 5 '18 at 22:53









      AAKAAK

      365




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