How To solve this type of inequation












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$begingroup$


Let $f$ be a regular $2pi-$periodic function .



How to find the functions that solve this inequality $a le f+f^{'}+f^{"} le b$ where $a,b in mathbb{R}_{+}$ .



Could you give me some books to deal with this type of problem?
Thanks










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$endgroup$












  • $begingroup$
    Since the function is periodic, can't you use a general fourier series and apply your condition to it?
    $endgroup$
    – Eddy
    Jan 1 at 16:32










  • $begingroup$
    thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
    $endgroup$
    – T A R I K
    Jan 1 at 16:36












  • $begingroup$
    What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
    $endgroup$
    – Winther
    Jan 1 at 16:46












  • $begingroup$
    thank you , i would like to Classifying all such functions
    $endgroup$
    – T A R I K
    Jan 1 at 17:23
















0












$begingroup$


Let $f$ be a regular $2pi-$periodic function .



How to find the functions that solve this inequality $a le f+f^{'}+f^{"} le b$ where $a,b in mathbb{R}_{+}$ .



Could you give me some books to deal with this type of problem?
Thanks










share|cite|improve this question









$endgroup$












  • $begingroup$
    Since the function is periodic, can't you use a general fourier series and apply your condition to it?
    $endgroup$
    – Eddy
    Jan 1 at 16:32










  • $begingroup$
    thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
    $endgroup$
    – T A R I K
    Jan 1 at 16:36












  • $begingroup$
    What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
    $endgroup$
    – Winther
    Jan 1 at 16:46












  • $begingroup$
    thank you , i would like to Classifying all such functions
    $endgroup$
    – T A R I K
    Jan 1 at 17:23














0












0








0





$begingroup$


Let $f$ be a regular $2pi-$periodic function .



How to find the functions that solve this inequality $a le f+f^{'}+f^{"} le b$ where $a,b in mathbb{R}_{+}$ .



Could you give me some books to deal with this type of problem?
Thanks










share|cite|improve this question









$endgroup$




Let $f$ be a regular $2pi-$periodic function .



How to find the functions that solve this inequality $a le f+f^{'}+f^{"} le b$ where $a,b in mathbb{R}_{+}$ .



Could you give me some books to deal with this type of problem?
Thanks







real-analysis inequality periodic-functions






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 1 at 16:23









T A R I KT A R I K

297




297












  • $begingroup$
    Since the function is periodic, can't you use a general fourier series and apply your condition to it?
    $endgroup$
    – Eddy
    Jan 1 at 16:32










  • $begingroup$
    thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
    $endgroup$
    – T A R I K
    Jan 1 at 16:36












  • $begingroup$
    What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
    $endgroup$
    – Winther
    Jan 1 at 16:46












  • $begingroup$
    thank you , i would like to Classifying all such functions
    $endgroup$
    – T A R I K
    Jan 1 at 17:23


















  • $begingroup$
    Since the function is periodic, can't you use a general fourier series and apply your condition to it?
    $endgroup$
    – Eddy
    Jan 1 at 16:32










  • $begingroup$
    thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
    $endgroup$
    – T A R I K
    Jan 1 at 16:36












  • $begingroup$
    What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
    $endgroup$
    – Winther
    Jan 1 at 16:46












  • $begingroup$
    thank you , i would like to Classifying all such functions
    $endgroup$
    – T A R I K
    Jan 1 at 17:23
















$begingroup$
Since the function is periodic, can't you use a general fourier series and apply your condition to it?
$endgroup$
– Eddy
Jan 1 at 16:32




$begingroup$
Since the function is periodic, can't you use a general fourier series and apply your condition to it?
$endgroup$
– Eddy
Jan 1 at 16:32












$begingroup$
thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
$endgroup$
– T A R I K
Jan 1 at 16:36






$begingroup$
thaanks ,yes but what type of information we can concloude about the fourier coefficients from the inequality " fourier series is less than a constant" ?
$endgroup$
– T A R I K
Jan 1 at 16:36














$begingroup$
What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
$endgroup$
– Winther
Jan 1 at 16:46






$begingroup$
What's the context, any special reason why you want to find such solutions? Classifying all such functions seems like a hard task. Finding some solutions is much easier. Take for example $f(x) = c + sum c_nsin(2pi nx)$ with $cin(a,b)$ and take $c_n$'s "small enough"
$endgroup$
– Winther
Jan 1 at 16:46














$begingroup$
thank you , i would like to Classifying all such functions
$endgroup$
– T A R I K
Jan 1 at 17:23




$begingroup$
thank you , i would like to Classifying all such functions
$endgroup$
– T A R I K
Jan 1 at 17:23










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