Hints on $lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$












1












$begingroup$


Let $B in mathcal{B}^{d}$ and $alphaneq 0$



Any ideas on how to show:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$



My idea using "simple sets":



Let $B:=[a_{1},b_{1}[times...times[a_{d},b_{d}[$ this means:



Note without loss of generality $alpha > 0$ otherwise switch intervals $[a,b[$ to $[alpha b,alpha a[$



$alpha B=[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[$



Therefore $lambda^{d}(alpha B)=prod_{i=1}^{d}(alpha b_{i}-alpha a_{i})=alpha^{d}prod_{i=1}^{d}( b_{i}- a_{i})=alphalambda^{d}(B)$



Since ${[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[}$ is a $cap-$stable generator of $mathcal{B}^{d}$ it follows:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$ for any $B in mathcal{B}^{d}$










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$endgroup$












  • $begingroup$
    Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
    $endgroup$
    – Did
    Jan 13 at 17:57










  • $begingroup$
    @Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
    $endgroup$
    – MinaThuma
    Jan 13 at 18:43










  • $begingroup$
    No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
    $endgroup$
    – Did
    Jan 13 at 18:45










  • $begingroup$
    @Did I have edited my question, is it correct?
    $endgroup$
    – MinaThuma
    Jan 13 at 19:01












  • $begingroup$
    Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
    $endgroup$
    – Did
    Jan 13 at 19:03
















1












$begingroup$


Let $B in mathcal{B}^{d}$ and $alphaneq 0$



Any ideas on how to show:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$



My idea using "simple sets":



Let $B:=[a_{1},b_{1}[times...times[a_{d},b_{d}[$ this means:



Note without loss of generality $alpha > 0$ otherwise switch intervals $[a,b[$ to $[alpha b,alpha a[$



$alpha B=[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[$



Therefore $lambda^{d}(alpha B)=prod_{i=1}^{d}(alpha b_{i}-alpha a_{i})=alpha^{d}prod_{i=1}^{d}( b_{i}- a_{i})=alphalambda^{d}(B)$



Since ${[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[}$ is a $cap-$stable generator of $mathcal{B}^{d}$ it follows:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$ for any $B in mathcal{B}^{d}$










share|cite|improve this question











$endgroup$












  • $begingroup$
    Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
    $endgroup$
    – Did
    Jan 13 at 17:57










  • $begingroup$
    @Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
    $endgroup$
    – MinaThuma
    Jan 13 at 18:43










  • $begingroup$
    No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
    $endgroup$
    – Did
    Jan 13 at 18:45










  • $begingroup$
    @Did I have edited my question, is it correct?
    $endgroup$
    – MinaThuma
    Jan 13 at 19:01












  • $begingroup$
    Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
    $endgroup$
    – Did
    Jan 13 at 19:03














1












1








1





$begingroup$


Let $B in mathcal{B}^{d}$ and $alphaneq 0$



Any ideas on how to show:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$



My idea using "simple sets":



Let $B:=[a_{1},b_{1}[times...times[a_{d},b_{d}[$ this means:



Note without loss of generality $alpha > 0$ otherwise switch intervals $[a,b[$ to $[alpha b,alpha a[$



$alpha B=[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[$



Therefore $lambda^{d}(alpha B)=prod_{i=1}^{d}(alpha b_{i}-alpha a_{i})=alpha^{d}prod_{i=1}^{d}( b_{i}- a_{i})=alphalambda^{d}(B)$



Since ${[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[}$ is a $cap-$stable generator of $mathcal{B}^{d}$ it follows:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$ for any $B in mathcal{B}^{d}$










share|cite|improve this question











$endgroup$




Let $B in mathcal{B}^{d}$ and $alphaneq 0$



Any ideas on how to show:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$



My idea using "simple sets":



Let $B:=[a_{1},b_{1}[times...times[a_{d},b_{d}[$ this means:



Note without loss of generality $alpha > 0$ otherwise switch intervals $[a,b[$ to $[alpha b,alpha a[$



$alpha B=[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[$



Therefore $lambda^{d}(alpha B)=prod_{i=1}^{d}(alpha b_{i}-alpha a_{i})=alpha^{d}prod_{i=1}^{d}( b_{i}- a_{i})=alphalambda^{d}(B)$



Since ${[alpha a_{1},alpha b_{1}[times...times[alpha a_{d},alpha b_{d}[}$ is a $cap-$stable generator of $mathcal{B}^{d}$ it follows:



$lambda^{d}(alpha B)=|alpha|^dlambda^{d}(B)$ for any $B in mathcal{B}^{d}$







real-analysis measure-theory lebesgue-integral lebesgue-measure






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share|cite|improve this question













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edited Jan 13 at 19:00







MinaThuma

















asked Jan 13 at 17:51









MinaThumaMinaThuma

27010




27010












  • $begingroup$
    Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
    $endgroup$
    – Did
    Jan 13 at 17:57










  • $begingroup$
    @Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
    $endgroup$
    – MinaThuma
    Jan 13 at 18:43










  • $begingroup$
    No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
    $endgroup$
    – Did
    Jan 13 at 18:45










  • $begingroup$
    @Did I have edited my question, is it correct?
    $endgroup$
    – MinaThuma
    Jan 13 at 19:01












  • $begingroup$
    Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
    $endgroup$
    – Did
    Jan 13 at 19:03


















  • $begingroup$
    Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
    $endgroup$
    – Did
    Jan 13 at 17:57










  • $begingroup$
    @Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
    $endgroup$
    – MinaThuma
    Jan 13 at 18:43










  • $begingroup$
    No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
    $endgroup$
    – Did
    Jan 13 at 18:45










  • $begingroup$
    @Did I have edited my question, is it correct?
    $endgroup$
    – MinaThuma
    Jan 13 at 19:01












  • $begingroup$
    Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
    $endgroup$
    – Did
    Jan 13 at 19:03
















$begingroup$
Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
$endgroup$
– Did
Jan 13 at 17:57




$begingroup$
Hint: Show that the result holds for simple sets, then consider the class of sets such that it holds.
$endgroup$
– Did
Jan 13 at 17:57












$begingroup$
@Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
$endgroup$
– MinaThuma
Jan 13 at 18:43




$begingroup$
@Did So $lambda^{d}(alpha B)=int_{mathbb R^{d}}chi_{alpha B}dlambda^{d}$ does not help? I am confused as to how to use your hint
$endgroup$
– MinaThuma
Jan 13 at 18:43












$begingroup$
No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
$endgroup$
– Did
Jan 13 at 18:45




$begingroup$
No it does not. Re my hint, it has two parts. Let me suggest to first concentrate on the first part, and then to turn to the second part.
$endgroup$
– Did
Jan 13 at 18:45












$begingroup$
@Did I have edited my question, is it correct?
$endgroup$
– MinaThuma
Jan 13 at 19:01






$begingroup$
@Did I have edited my question, is it correct?
$endgroup$
– MinaThuma
Jan 13 at 19:01














$begingroup$
Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
$endgroup$
– Did
Jan 13 at 19:03




$begingroup$
Yes, although you might be more explicit about how you deduce the result for the class of Borel sets from the result for the smaller class.
$endgroup$
– Did
Jan 13 at 19:03










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