Whether supremum and partial derivative can be interchanged?












3














Recently, I study replica method derived from statistical physics. I have a confusion on following equation
begin{align}
mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M}lim_{taurightarrow 0}frac{partial }{partial tau} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}right}
end{align}

where $mathbf{Q}=(c-q)mathbf{I}_{tau+1}+qboldsymbol{ee}^T$ and $tilde{mathbf{Q}}=(tilde{c}-tilde{q})mathbf{I}_{tau+1}+tilde{q}boldsymbol{ee}^T$ with $boldsymbol{e}in mathbb{R}^{tau+1}$ denoting a column vector whose elements are all 1.



In the most of paper about replica method, they always change the sup, inf and partial derivative like following
begin{align}
mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{
lim_{taurightarrow 0}frac{partial }{partial tau}left[
alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}
right]
right}
end{align}



What I have thought?



As far as I know, I consider that both $sup$ and $inf$ are one limit. Generally, $lim$ and partial derivative can be interchanged.



I hope you can help me. This is extremely important for me. Thank you!










share|cite|improve this question





























    3














    Recently, I study replica method derived from statistical physics. I have a confusion on following equation
    begin{align}
    mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M}lim_{taurightarrow 0}frac{partial }{partial tau} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}right}
    end{align}

    where $mathbf{Q}=(c-q)mathbf{I}_{tau+1}+qboldsymbol{ee}^T$ and $tilde{mathbf{Q}}=(tilde{c}-tilde{q})mathbf{I}_{tau+1}+tilde{q}boldsymbol{ee}^T$ with $boldsymbol{e}in mathbb{R}^{tau+1}$ denoting a column vector whose elements are all 1.



    In the most of paper about replica method, they always change the sup, inf and partial derivative like following
    begin{align}
    mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{
    lim_{taurightarrow 0}frac{partial }{partial tau}left[
    alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}
    right]
    right}
    end{align}



    What I have thought?



    As far as I know, I consider that both $sup$ and $inf$ are one limit. Generally, $lim$ and partial derivative can be interchanged.



    I hope you can help me. This is extremely important for me. Thank you!










    share|cite|improve this question



























      3












      3








      3


      1





      Recently, I study replica method derived from statistical physics. I have a confusion on following equation
      begin{align}
      mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M}lim_{taurightarrow 0}frac{partial }{partial tau} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}right}
      end{align}

      where $mathbf{Q}=(c-q)mathbf{I}_{tau+1}+qboldsymbol{ee}^T$ and $tilde{mathbf{Q}}=(tilde{c}-tilde{q})mathbf{I}_{tau+1}+tilde{q}boldsymbol{ee}^T$ with $boldsymbol{e}in mathbb{R}^{tau+1}$ denoting a column vector whose elements are all 1.



      In the most of paper about replica method, they always change the sup, inf and partial derivative like following
      begin{align}
      mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{
      lim_{taurightarrow 0}frac{partial }{partial tau}left[
      alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}
      right]
      right}
      end{align}



      What I have thought?



      As far as I know, I consider that both $sup$ and $inf$ are one limit. Generally, $lim$ and partial derivative can be interchanged.



      I hope you can help me. This is extremely important for me. Thank you!










      share|cite|improve this question















      Recently, I study replica method derived from statistical physics. I have a confusion on following equation
      begin{align}
      mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M}lim_{taurightarrow 0}frac{partial }{partial tau} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}right}
      end{align}

      where $mathbf{Q}=(c-q)mathbf{I}_{tau+1}+qboldsymbol{ee}^T$ and $tilde{mathbf{Q}}=(tilde{c}-tilde{q})mathbf{I}_{tau+1}+tilde{q}boldsymbol{ee}^T$ with $boldsymbol{e}in mathbb{R}^{tau+1}$ denoting a column vector whose elements are all 1.



      In the most of paper about replica method, they always change the sup, inf and partial derivative like following
      begin{align}
      mathcal{F}=-lim_{Mrightarrow infty}frac{1}{M} underset{mathbf{Q},tilde{mathbf{Q}}}{supinf}left{
      lim_{taurightarrow 0}frac{partial }{partial tau}left[
      alpha^{-1}G(mathbf{Q})-text{tr}left{mathbf{Q}tilde{mathbf{Q}}right}-frac{1}{M}log mathbb{E}_{mathbf{X}}left{exp left[text{tr}(mathbf{X}tilde{mathbf{Q}}mathbf{X}^T)right]right}
      right]
      right}
      end{align}



      What I have thought?



      As far as I know, I consider that both $sup$ and $inf$ are one limit. Generally, $lim$ and partial derivative can be interchanged.



      I hope you can help me. This is extremely important for me. Thank you!







      partial-derivative supremum-and-infimum






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      share|cite|improve this question













      share|cite|improve this question




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      edited Nov 20 at 7:37

























      asked Nov 20 at 2:55









      Qiuyun

      778




      778



























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