Existence minimizer for total variation over measures












2












$begingroup$


I want to prove that there exists a minimizer to the following problem
$$
min || mu ||_{text{TV}} text{ such that } mathcal{F} mu = y
$$



where $mu in mathcal{M}([0,1])$, the space of Radon measures in the interval $[0,1]$, and $mathcal{F}: mathcal{M}([0,1]) to mathbb{C}^n$ is some linear operator, to which we know that $mathcal{F}^{-1} y neq { emptyset }$.



Typically for convex problems like this, I would approach it by using convexity and lower semi-continuity of the total variation norm. But since the underlying space is (I think) not reflexive, there is no weak compacity for closed, convex, bounded sets.










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$endgroup$

















    2












    $begingroup$


    I want to prove that there exists a minimizer to the following problem
    $$
    min || mu ||_{text{TV}} text{ such that } mathcal{F} mu = y
    $$



    where $mu in mathcal{M}([0,1])$, the space of Radon measures in the interval $[0,1]$, and $mathcal{F}: mathcal{M}([0,1]) to mathbb{C}^n$ is some linear operator, to which we know that $mathcal{F}^{-1} y neq { emptyset }$.



    Typically for convex problems like this, I would approach it by using convexity and lower semi-continuity of the total variation norm. But since the underlying space is (I think) not reflexive, there is no weak compacity for closed, convex, bounded sets.










    share|cite|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      I want to prove that there exists a minimizer to the following problem
      $$
      min || mu ||_{text{TV}} text{ such that } mathcal{F} mu = y
      $$



      where $mu in mathcal{M}([0,1])$, the space of Radon measures in the interval $[0,1]$, and $mathcal{F}: mathcal{M}([0,1]) to mathbb{C}^n$ is some linear operator, to which we know that $mathcal{F}^{-1} y neq { emptyset }$.



      Typically for convex problems like this, I would approach it by using convexity and lower semi-continuity of the total variation norm. But since the underlying space is (I think) not reflexive, there is no weak compacity for closed, convex, bounded sets.










      share|cite|improve this question











      $endgroup$




      I want to prove that there exists a minimizer to the following problem
      $$
      min || mu ||_{text{TV}} text{ such that } mathcal{F} mu = y
      $$



      where $mu in mathcal{M}([0,1])$, the space of Radon measures in the interval $[0,1]$, and $mathcal{F}: mathcal{M}([0,1]) to mathbb{C}^n$ is some linear operator, to which we know that $mathcal{F}^{-1} y neq { emptyset }$.



      Typically for convex problems like this, I would approach it by using convexity and lower semi-continuity of the total variation norm. But since the underlying space is (I think) not reflexive, there is no weak compacity for closed, convex, bounded sets.







      measure-theory optimization convex-optimization total-variation






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      edited Jan 22 at 12:40







      pancho

















      asked Jan 22 at 10:32









      panchopancho

      531210




      531210






















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          $begingroup$

          Typically, you can use that $mathcal M(([0,1])$ is the dual space of the separable space $C([0,1])$. Hence, for every bounded sequence you can extract weak-$*$ convergent subsequences. If $mathcal F$ is also continuous w.r.t. the weak-$*$ convergent sequences, then you can do the usual arguments. If you do not know this (additional) continuity of $mathcal F$, the existence of minimizers may fail.






          share|cite|improve this answer









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          • $begingroup$
            Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
            $endgroup$
            – pancho
            Jan 24 at 9:40











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          1 Answer
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          1 Answer
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          active

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          active

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          active

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          1












          $begingroup$

          Typically, you can use that $mathcal M(([0,1])$ is the dual space of the separable space $C([0,1])$. Hence, for every bounded sequence you can extract weak-$*$ convergent subsequences. If $mathcal F$ is also continuous w.r.t. the weak-$*$ convergent sequences, then you can do the usual arguments. If you do not know this (additional) continuity of $mathcal F$, the existence of minimizers may fail.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
            $endgroup$
            – pancho
            Jan 24 at 9:40
















          1












          $begingroup$

          Typically, you can use that $mathcal M(([0,1])$ is the dual space of the separable space $C([0,1])$. Hence, for every bounded sequence you can extract weak-$*$ convergent subsequences. If $mathcal F$ is also continuous w.r.t. the weak-$*$ convergent sequences, then you can do the usual arguments. If you do not know this (additional) continuity of $mathcal F$, the existence of minimizers may fail.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
            $endgroup$
            – pancho
            Jan 24 at 9:40














          1












          1








          1





          $begingroup$

          Typically, you can use that $mathcal M(([0,1])$ is the dual space of the separable space $C([0,1])$. Hence, for every bounded sequence you can extract weak-$*$ convergent subsequences. If $mathcal F$ is also continuous w.r.t. the weak-$*$ convergent sequences, then you can do the usual arguments. If you do not know this (additional) continuity of $mathcal F$, the existence of minimizers may fail.






          share|cite|improve this answer









          $endgroup$



          Typically, you can use that $mathcal M(([0,1])$ is the dual space of the separable space $C([0,1])$. Hence, for every bounded sequence you can extract weak-$*$ convergent subsequences. If $mathcal F$ is also continuous w.r.t. the weak-$*$ convergent sequences, then you can do the usual arguments. If you do not know this (additional) continuity of $mathcal F$, the existence of minimizers may fail.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 24 at 7:59









          gerwgerw

          19.6k11334




          19.6k11334












          • $begingroup$
            Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
            $endgroup$
            – pancho
            Jan 24 at 9:40


















          • $begingroup$
            Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
            $endgroup$
            – pancho
            Jan 24 at 9:40
















          $begingroup$
          Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
          $endgroup$
          – pancho
          Jan 24 at 9:40




          $begingroup$
          Indeed, $mathcal{F}$ is in particular defined as applying the measures to a family of predefined $C([0,1])$, therefore weak-* continuity is also present. Thank you !
          $endgroup$
          – pancho
          Jan 24 at 9:40


















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