show that $Delta in mathcal{B} otimes mathcal{P}$












1












$begingroup$


let $lambda$ be the Lebesgue measure on the sigma algebra $ mathcal{B}
= mathcal{B} ([0,1])$
and let $mu$ be the counting measure on the sigma algebra $ mathcal{P} = mathcal{P}([0,1])$



let $Delta = {(x,x), mid , x in [0,1] }$



show that $Delta in mathcal{B} otimes mathcal{P}$



one way to prove it would be to write it as $Delta_1 times Delta_2$ such that $Delta_1 in mathcal{B} $ and $Delta_2 in mathcal{P} $



which I couldn't do



my attempt :



$Delta = bigcup_{x in [0,1]} {(x,x)} $



and ${(x,x)} = {x} times {x } in mathcal{B} times mathcal{P} $



now if the union was countable I would be done but it's not.



hints or any kind help are very welcome.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    $Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
    $endgroup$
    – Mindlack
    Jan 13 at 23:41
















1












$begingroup$


let $lambda$ be the Lebesgue measure on the sigma algebra $ mathcal{B}
= mathcal{B} ([0,1])$
and let $mu$ be the counting measure on the sigma algebra $ mathcal{P} = mathcal{P}([0,1])$



let $Delta = {(x,x), mid , x in [0,1] }$



show that $Delta in mathcal{B} otimes mathcal{P}$



one way to prove it would be to write it as $Delta_1 times Delta_2$ such that $Delta_1 in mathcal{B} $ and $Delta_2 in mathcal{P} $



which I couldn't do



my attempt :



$Delta = bigcup_{x in [0,1]} {(x,x)} $



and ${(x,x)} = {x} times {x } in mathcal{B} times mathcal{P} $



now if the union was countable I would be done but it's not.



hints or any kind help are very welcome.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    $Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
    $endgroup$
    – Mindlack
    Jan 13 at 23:41














1












1








1





$begingroup$


let $lambda$ be the Lebesgue measure on the sigma algebra $ mathcal{B}
= mathcal{B} ([0,1])$
and let $mu$ be the counting measure on the sigma algebra $ mathcal{P} = mathcal{P}([0,1])$



let $Delta = {(x,x), mid , x in [0,1] }$



show that $Delta in mathcal{B} otimes mathcal{P}$



one way to prove it would be to write it as $Delta_1 times Delta_2$ such that $Delta_1 in mathcal{B} $ and $Delta_2 in mathcal{P} $



which I couldn't do



my attempt :



$Delta = bigcup_{x in [0,1]} {(x,x)} $



and ${(x,x)} = {x} times {x } in mathcal{B} times mathcal{P} $



now if the union was countable I would be done but it's not.



hints or any kind help are very welcome.










share|cite|improve this question











$endgroup$




let $lambda$ be the Lebesgue measure on the sigma algebra $ mathcal{B}
= mathcal{B} ([0,1])$
and let $mu$ be the counting measure on the sigma algebra $ mathcal{P} = mathcal{P}([0,1])$



let $Delta = {(x,x), mid , x in [0,1] }$



show that $Delta in mathcal{B} otimes mathcal{P}$



one way to prove it would be to write it as $Delta_1 times Delta_2$ such that $Delta_1 in mathcal{B} $ and $Delta_2 in mathcal{P} $



which I couldn't do



my attempt :



$Delta = bigcup_{x in [0,1]} {(x,x)} $



and ${(x,x)} = {x} times {x } in mathcal{B} times mathcal{P} $



now if the union was countable I would be done but it's not.



hints or any kind help are very welcome.







measure-theory lebesgue-measure






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edited Jan 13 at 23:09









Bernard

121k740116




121k740116










asked Jan 13 at 23:05









rapidracimrapidracim

1,7241419




1,7241419








  • 1




    $begingroup$
    $Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
    $endgroup$
    – Mindlack
    Jan 13 at 23:41














  • 1




    $begingroup$
    $Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
    $endgroup$
    – Mindlack
    Jan 13 at 23:41








1




1




$begingroup$
$Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
$endgroup$
– Mindlack
Jan 13 at 23:41




$begingroup$
$Delta$ is closed in $[0,1]^2$ so is contained in $mathcal{B}([0,1]^2)=mathcal{B} otimes mathcal{B} subset mathcal{B} otimes mathcal{P}$.
$endgroup$
– Mindlack
Jan 13 at 23:41










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$begingroup$

Can you verify that $Delta^{c}=(cup_q [(y>qcap (x<q)]) cup (cup_q [(x>qcap (y<q)])$ where $q$ ranges over rational numbers and conclude that $Delta^{c}$, hence $Delta$ belongs to $mathcal B otimes mathcal P$?. [$Delta^{c}$ is the complement of $Delta $]






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    $begingroup$

    Can you verify that $Delta^{c}=(cup_q [(y>qcap (x<q)]) cup (cup_q [(x>qcap (y<q)])$ where $q$ ranges over rational numbers and conclude that $Delta^{c}$, hence $Delta$ belongs to $mathcal B otimes mathcal P$?. [$Delta^{c}$ is the complement of $Delta $]






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Can you verify that $Delta^{c}=(cup_q [(y>qcap (x<q)]) cup (cup_q [(x>qcap (y<q)])$ where $q$ ranges over rational numbers and conclude that $Delta^{c}$, hence $Delta$ belongs to $mathcal B otimes mathcal P$?. [$Delta^{c}$ is the complement of $Delta $]






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Can you verify that $Delta^{c}=(cup_q [(y>qcap (x<q)]) cup (cup_q [(x>qcap (y<q)])$ where $q$ ranges over rational numbers and conclude that $Delta^{c}$, hence $Delta$ belongs to $mathcal B otimes mathcal P$?. [$Delta^{c}$ is the complement of $Delta $]






        share|cite|improve this answer









        $endgroup$



        Can you verify that $Delta^{c}=(cup_q [(y>qcap (x<q)]) cup (cup_q [(x>qcap (y<q)])$ where $q$ ranges over rational numbers and conclude that $Delta^{c}$, hence $Delta$ belongs to $mathcal B otimes mathcal P$?. [$Delta^{c}$ is the complement of $Delta $]







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 13 at 23:48









        Kavi Rama MurthyKavi Rama Murthy

        60.2k42161




        60.2k42161






























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