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Approximate a Lipschitz function by an affine function


Extending a $k$-lipschitz functionAffine Function ProofsLipschitz function and lebusgue measure problemHow to approximate a globally Lipschitz function by differentiable functions with bounded derivatives?Approximate the unit ball in an infinite-dimensional Hilbert space, by compact sets?Show a function is $K$-LipschitzApproximating Lipschitz Functions by $C^1$ functionsWhen is a locally Lipschitz function globally Lipschitz?Can every Lipschitz function be approximated by functions of constant variation?Lipschitz continuity of vector saturation













1












$begingroup$


Suppose $f: A rightarrow mathbbR$ is a Lipschitz function (Lipschitz constant $L$), and $A$ is a bounded subset of $mathbbR^n$ (i.e., for any $x in A, ||x||<M$).



If I am going to use an affine function to approximate this Lipschitz function, what is the $ell 2$ norm of their difference? That is, what is



$$sup_f inf_g ||f-g|| = sup_f inf_g int_A (f(x) -g(x))^2 dx$$



$f$ is defined above, and $g$ is an affine function defined on $A$.










share|cite|improve this question











$endgroup$











  • $begingroup$
    Are you sure such a supremum is finite ?
    $endgroup$
    – TheSilverDoe
    Mar 10 at 20:59















1












$begingroup$


Suppose $f: A rightarrow mathbbR$ is a Lipschitz function (Lipschitz constant $L$), and $A$ is a bounded subset of $mathbbR^n$ (i.e., for any $x in A, ||x||<M$).



If I am going to use an affine function to approximate this Lipschitz function, what is the $ell 2$ norm of their difference? That is, what is



$$sup_f inf_g ||f-g|| = sup_f inf_g int_A (f(x) -g(x))^2 dx$$



$f$ is defined above, and $g$ is an affine function defined on $A$.










share|cite|improve this question











$endgroup$











  • $begingroup$
    Are you sure such a supremum is finite ?
    $endgroup$
    – TheSilverDoe
    Mar 10 at 20:59













1












1








1





$begingroup$


Suppose $f: A rightarrow mathbbR$ is a Lipschitz function (Lipschitz constant $L$), and $A$ is a bounded subset of $mathbbR^n$ (i.e., for any $x in A, ||x||<M$).



If I am going to use an affine function to approximate this Lipschitz function, what is the $ell 2$ norm of their difference? That is, what is



$$sup_f inf_g ||f-g|| = sup_f inf_g int_A (f(x) -g(x))^2 dx$$



$f$ is defined above, and $g$ is an affine function defined on $A$.










share|cite|improve this question











$endgroup$




Suppose $f: A rightarrow mathbbR$ is a Lipschitz function (Lipschitz constant $L$), and $A$ is a bounded subset of $mathbbR^n$ (i.e., for any $x in A, ||x||<M$).



If I am going to use an affine function to approximate this Lipschitz function, what is the $ell 2$ norm of their difference? That is, what is



$$sup_f inf_g ||f-g|| = sup_f inf_g int_A (f(x) -g(x))^2 dx$$



$f$ is defined above, and $g$ is an affine function defined on $A$.







real-analysis functional-analysis measure-theory lebesgue-measure






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 10 at 21:07







coolcat

















asked Mar 10 at 20:55









coolcatcoolcat

1159




1159











  • $begingroup$
    Are you sure such a supremum is finite ?
    $endgroup$
    – TheSilverDoe
    Mar 10 at 20:59
















  • $begingroup$
    Are you sure such a supremum is finite ?
    $endgroup$
    – TheSilverDoe
    Mar 10 at 20:59















$begingroup$
Are you sure such a supremum is finite ?
$endgroup$
– TheSilverDoe
Mar 10 at 20:59




$begingroup$
Are you sure such a supremum is finite ?
$endgroup$
– TheSilverDoe
Mar 10 at 20:59










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