About Sobolev Space definition.












2












$begingroup$


I would like to know if this two definitions for Sobolev Spaces are equivalent:
$H_2^m([a,b]):={f: f',...,f^{(m-1)} text{absolutely continuous}, int _a^b (f^{(m)})^2dx<infty }$



and $H_2^m([a,b])$ contains all functions $f$ such that $D^mu f in L_2([a,b])$ for $mu=0,1,...,m$



The first definition requires the $m$th derivative to be square integrable, while in the second one all derivatives (up to order m) must belong to $L_2([a,b])$ and no continuity is required.
I guess it has to do with the fact that absolute continuity is required, but I want to be sure that both are valid.
Any hint will be greatly appreciated.










share|cite|improve this question









$endgroup$












  • $begingroup$
    @orange en.wikipedia.org/wiki/Absolute_continuity
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 20:01










  • $begingroup$
    Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 22:00










  • $begingroup$
    @orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
    $endgroup$
    – Ramiro Scorolli
    Dec 15 '18 at 9:48
















2












$begingroup$


I would like to know if this two definitions for Sobolev Spaces are equivalent:
$H_2^m([a,b]):={f: f',...,f^{(m-1)} text{absolutely continuous}, int _a^b (f^{(m)})^2dx<infty }$



and $H_2^m([a,b])$ contains all functions $f$ such that $D^mu f in L_2([a,b])$ for $mu=0,1,...,m$



The first definition requires the $m$th derivative to be square integrable, while in the second one all derivatives (up to order m) must belong to $L_2([a,b])$ and no continuity is required.
I guess it has to do with the fact that absolute continuity is required, but I want to be sure that both are valid.
Any hint will be greatly appreciated.










share|cite|improve this question









$endgroup$












  • $begingroup$
    @orange en.wikipedia.org/wiki/Absolute_continuity
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 20:01










  • $begingroup$
    Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 22:00










  • $begingroup$
    @orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
    $endgroup$
    – Ramiro Scorolli
    Dec 15 '18 at 9:48














2












2








2


2



$begingroup$


I would like to know if this two definitions for Sobolev Spaces are equivalent:
$H_2^m([a,b]):={f: f',...,f^{(m-1)} text{absolutely continuous}, int _a^b (f^{(m)})^2dx<infty }$



and $H_2^m([a,b])$ contains all functions $f$ such that $D^mu f in L_2([a,b])$ for $mu=0,1,...,m$



The first definition requires the $m$th derivative to be square integrable, while in the second one all derivatives (up to order m) must belong to $L_2([a,b])$ and no continuity is required.
I guess it has to do with the fact that absolute continuity is required, but I want to be sure that both are valid.
Any hint will be greatly appreciated.










share|cite|improve this question









$endgroup$




I would like to know if this two definitions for Sobolev Spaces are equivalent:
$H_2^m([a,b]):={f: f',...,f^{(m-1)} text{absolutely continuous}, int _a^b (f^{(m)})^2dx<infty }$



and $H_2^m([a,b])$ contains all functions $f$ such that $D^mu f in L_2([a,b])$ for $mu=0,1,...,m$



The first definition requires the $m$th derivative to be square integrable, while in the second one all derivatives (up to order m) must belong to $L_2([a,b])$ and no continuity is required.
I guess it has to do with the fact that absolute continuity is required, but I want to be sure that both are valid.
Any hint will be greatly appreciated.







functional-analysis vector-spaces sobolev-spaces






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Dec 14 '18 at 16:24









Ramiro ScorolliRamiro Scorolli

644114




644114












  • $begingroup$
    @orange en.wikipedia.org/wiki/Absolute_continuity
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 20:01










  • $begingroup$
    Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 22:00










  • $begingroup$
    @orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
    $endgroup$
    – Ramiro Scorolli
    Dec 15 '18 at 9:48


















  • $begingroup$
    @orange en.wikipedia.org/wiki/Absolute_continuity
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 20:01










  • $begingroup$
    Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
    $endgroup$
    – Ramiro Scorolli
    Dec 14 '18 at 22:00










  • $begingroup$
    @orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
    $endgroup$
    – Ramiro Scorolli
    Dec 15 '18 at 9:48
















$begingroup$
@orange en.wikipedia.org/wiki/Absolute_continuity
$endgroup$
– Ramiro Scorolli
Dec 14 '18 at 20:01




$begingroup$
@orange en.wikipedia.org/wiki/Absolute_continuity
$endgroup$
– Ramiro Scorolli
Dec 14 '18 at 20:01












$begingroup$
Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
$endgroup$
– Ramiro Scorolli
Dec 14 '18 at 22:00




$begingroup$
Or could it be that the second is not actually a definition in the formal sense, but just a state? It came to my mind that maybe the author was not actually defining the space but just making a characterization
$endgroup$
– Ramiro Scorolli
Dec 14 '18 at 22:00












$begingroup$
@orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
$endgroup$
– Ramiro Scorolli
Dec 15 '18 at 9:48




$begingroup$
@orange this is the article where the second statement is made, link.springer.com/article/10.1023/A:1019250217452
$endgroup$
– Ramiro Scorolli
Dec 15 '18 at 9:48










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