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Laurent series and tensor


Problem with integration of $1$-form on surfaceResidue of $mathrmexp (z+1/z)/((z-z_1)(z-z_2))$ at z=0Contour Integration - my solution for real integral is complex?Residue Theorem for trigonometric integrals.Suppose that $F$ is analytic in a convex domain $G$ and $Re(F')>0$. Prove or disprove: $F$ is univalent in $G$Multivariate/multidimensional residuesProbably incorrect method of integration gives the correct result. Why?How to view this pseudocode in math symbols?compute residual of $A/(overlinez-overlinelambda_1)$Show that $iint_gamma Arg(z)dz=fracpi2+ln2$













0












$begingroup$


Let us begin with the complex vector space
beginequation
V_z=Bigomegain mathbbC[[z,z^-1]]dz mid operatornameRes_z=0 omega (z)Big
endequation



We could define the tensor product of $V_z_1 otimes V_z_2$.



My question is why $$omega_0,2:= fracdz_1 dz_2(z_1 - z_2)^2$$ does not belong to $V_z_1 otimes V_z_2$.



Residue of $omega_0,2$ at $z_1 =0 , z_2 =0 $ is zero. What is going here?










share|cite|improve this question











$endgroup$
















    0












    $begingroup$


    Let us begin with the complex vector space
    beginequation
    V_z=Bigomegain mathbbC[[z,z^-1]]dz mid operatornameRes_z=0 omega (z)Big
    endequation



    We could define the tensor product of $V_z_1 otimes V_z_2$.



    My question is why $$omega_0,2:= fracdz_1 dz_2(z_1 - z_2)^2$$ does not belong to $V_z_1 otimes V_z_2$.



    Residue of $omega_0,2$ at $z_1 =0 , z_2 =0 $ is zero. What is going here?










    share|cite|improve this question











    $endgroup$














      0












      0








      0





      $begingroup$


      Let us begin with the complex vector space
      beginequation
      V_z=Bigomegain mathbbC[[z,z^-1]]dz mid operatornameRes_z=0 omega (z)Big
      endequation



      We could define the tensor product of $V_z_1 otimes V_z_2$.



      My question is why $$omega_0,2:= fracdz_1 dz_2(z_1 - z_2)^2$$ does not belong to $V_z_1 otimes V_z_2$.



      Residue of $omega_0,2$ at $z_1 =0 , z_2 =0 $ is zero. What is going here?










      share|cite|improve this question











      $endgroup$




      Let us begin with the complex vector space
      beginequation
      V_z=Bigomegain mathbbC[[z,z^-1]]dz mid operatornameRes_z=0 omega (z)Big
      endequation



      We could define the tensor product of $V_z_1 otimes V_z_2$.



      My question is why $$omega_0,2:= fracdz_1 dz_2(z_1 - z_2)^2$$ does not belong to $V_z_1 otimes V_z_2$.



      Residue of $omega_0,2$ at $z_1 =0 , z_2 =0 $ is zero. What is going here?







      complex-analysis meromorphic-functions






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Mar 24 at 1:39









      Andrews

      1,2812422




      1,2812422










      asked Mar 22 at 3:43









      GGTGGT

      485311




      485311




















          1 Answer
          1






          active

          oldest

          votes


















          1












          $begingroup$

          The tensor product consists of elements
          $$f(z_1)g(z_2),dz_1,dz_2$$
          where $f$ and $g$ are Laurent series satisfying your residue condition.
          But
          $$h(z_1,z_2)=frac1(z_1-z_2)^2$$
          cannot be written as a product of a Laurent series in $z_1$ and
          a Laurent series in $z_2$. Nothing mysterious about that; most functions
          of two variables are not products of two functions of one variable.






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Is this obvious in this case it can't be written? Is there some proof?
            $endgroup$
            – GGT
            Mar 24 at 11:58










          • $begingroup$
            For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
            $endgroup$
            – Lord Shark the Unknown
            Mar 24 at 12:03











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          1 Answer
          1






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          active

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          active

          oldest

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          1












          $begingroup$

          The tensor product consists of elements
          $$f(z_1)g(z_2),dz_1,dz_2$$
          where $f$ and $g$ are Laurent series satisfying your residue condition.
          But
          $$h(z_1,z_2)=frac1(z_1-z_2)^2$$
          cannot be written as a product of a Laurent series in $z_1$ and
          a Laurent series in $z_2$. Nothing mysterious about that; most functions
          of two variables are not products of two functions of one variable.






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Is this obvious in this case it can't be written? Is there some proof?
            $endgroup$
            – GGT
            Mar 24 at 11:58










          • $begingroup$
            For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
            $endgroup$
            – Lord Shark the Unknown
            Mar 24 at 12:03















          1












          $begingroup$

          The tensor product consists of elements
          $$f(z_1)g(z_2),dz_1,dz_2$$
          where $f$ and $g$ are Laurent series satisfying your residue condition.
          But
          $$h(z_1,z_2)=frac1(z_1-z_2)^2$$
          cannot be written as a product of a Laurent series in $z_1$ and
          a Laurent series in $z_2$. Nothing mysterious about that; most functions
          of two variables are not products of two functions of one variable.






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Is this obvious in this case it can't be written? Is there some proof?
            $endgroup$
            – GGT
            Mar 24 at 11:58










          • $begingroup$
            For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
            $endgroup$
            – Lord Shark the Unknown
            Mar 24 at 12:03













          1












          1








          1





          $begingroup$

          The tensor product consists of elements
          $$f(z_1)g(z_2),dz_1,dz_2$$
          where $f$ and $g$ are Laurent series satisfying your residue condition.
          But
          $$h(z_1,z_2)=frac1(z_1-z_2)^2$$
          cannot be written as a product of a Laurent series in $z_1$ and
          a Laurent series in $z_2$. Nothing mysterious about that; most functions
          of two variables are not products of two functions of one variable.






          share|cite|improve this answer









          $endgroup$



          The tensor product consists of elements
          $$f(z_1)g(z_2),dz_1,dz_2$$
          where $f$ and $g$ are Laurent series satisfying your residue condition.
          But
          $$h(z_1,z_2)=frac1(z_1-z_2)^2$$
          cannot be written as a product of a Laurent series in $z_1$ and
          a Laurent series in $z_2$. Nothing mysterious about that; most functions
          of two variables are not products of two functions of one variable.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Mar 24 at 5:57









          Lord Shark the UnknownLord Shark the Unknown

          108k1162135




          108k1162135











          • $begingroup$
            Is this obvious in this case it can't be written? Is there some proof?
            $endgroup$
            – GGT
            Mar 24 at 11:58










          • $begingroup$
            For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
            $endgroup$
            – Lord Shark the Unknown
            Mar 24 at 12:03
















          • $begingroup$
            Is this obvious in this case it can't be written? Is there some proof?
            $endgroup$
            – GGT
            Mar 24 at 11:58










          • $begingroup$
            For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
            $endgroup$
            – Lord Shark the Unknown
            Mar 24 at 12:03















          $begingroup$
          Is this obvious in this case it can't be written? Is there some proof?
          $endgroup$
          – GGT
          Mar 24 at 11:58




          $begingroup$
          Is this obvious in this case it can't be written? Is there some proof?
          $endgroup$
          – GGT
          Mar 24 at 11:58












          $begingroup$
          For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
          $endgroup$
          – Lord Shark the Unknown
          Mar 24 at 12:03




          $begingroup$
          For an $h$ to have a such a factorisation one needs $f(z_1,z_2)f(z_1',z_2')=f(z_1,z_2')f(z_1',z_2)$ etc.
          $endgroup$
          – Lord Shark the Unknown
          Mar 24 at 12:03

















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