Benefits of choosing a Hamel bases for $L^p$ including a specific linearly independent subset

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According to the book I am studying (Royden & Fitzpatrick):




We can infer from Zorn's Lemma that every linear space possesses a Hamel basis.




A Hamel Basis is defined as a subset $mathcalB $ of a linear space $X$ provided each vector in $X$ is expressible as a unique $bffinite$ linear combination of vectors in $mathcalB$.



When I first read about the concept of Hamel bases (compared to other sets referred to as basis), I recognized that bases of finite spaces are Hamel basis, and that, for example, $x^k_k=0^infty$ is a Hamel basis of $mathbbR[x]$, the infinite-dimensional space of polynomials with real coefficients.



As comments have pointed out, there might not be a Hamel basis that is explicit to state for other common infinite-dimensional linear spaces ($ell^p$ or $L^p$) - their Hamel bases would need to be uncountable.



However, even if we cannot explicitly characterize the whole basis, could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'? (For example, include $ x^k_k=0^infty$ in the Hamel basis for $L^p([a,b])$). If so, what are the applications of this fact?







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  • 1




    When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
    – i707107
    Jul 29 at 5:32










  • Possible duplicate of A Hamel basis for $ell^p$?
    – adfriedman
    Jul 29 at 6:02










  • Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
    – ertl
    Jul 29 at 6:26










  • Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
    – mechanodroid
    Jul 29 at 12:38















up vote
1
down vote

favorite












According to the book I am studying (Royden & Fitzpatrick):




We can infer from Zorn's Lemma that every linear space possesses a Hamel basis.




A Hamel Basis is defined as a subset $mathcalB $ of a linear space $X$ provided each vector in $X$ is expressible as a unique $bffinite$ linear combination of vectors in $mathcalB$.



When I first read about the concept of Hamel bases (compared to other sets referred to as basis), I recognized that bases of finite spaces are Hamel basis, and that, for example, $x^k_k=0^infty$ is a Hamel basis of $mathbbR[x]$, the infinite-dimensional space of polynomials with real coefficients.



As comments have pointed out, there might not be a Hamel basis that is explicit to state for other common infinite-dimensional linear spaces ($ell^p$ or $L^p$) - their Hamel bases would need to be uncountable.



However, even if we cannot explicitly characterize the whole basis, could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'? (For example, include $ x^k_k=0^infty$ in the Hamel basis for $L^p([a,b])$). If so, what are the applications of this fact?







share|cite|improve this question

















  • 1




    When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
    – i707107
    Jul 29 at 5:32










  • Possible duplicate of A Hamel basis for $ell^p$?
    – adfriedman
    Jul 29 at 6:02










  • Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
    – ertl
    Jul 29 at 6:26










  • Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
    – mechanodroid
    Jul 29 at 12:38













up vote
1
down vote

favorite









up vote
1
down vote

favorite











According to the book I am studying (Royden & Fitzpatrick):




We can infer from Zorn's Lemma that every linear space possesses a Hamel basis.




A Hamel Basis is defined as a subset $mathcalB $ of a linear space $X$ provided each vector in $X$ is expressible as a unique $bffinite$ linear combination of vectors in $mathcalB$.



When I first read about the concept of Hamel bases (compared to other sets referred to as basis), I recognized that bases of finite spaces are Hamel basis, and that, for example, $x^k_k=0^infty$ is a Hamel basis of $mathbbR[x]$, the infinite-dimensional space of polynomials with real coefficients.



As comments have pointed out, there might not be a Hamel basis that is explicit to state for other common infinite-dimensional linear spaces ($ell^p$ or $L^p$) - their Hamel bases would need to be uncountable.



However, even if we cannot explicitly characterize the whole basis, could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'? (For example, include $ x^k_k=0^infty$ in the Hamel basis for $L^p([a,b])$). If so, what are the applications of this fact?







share|cite|improve this question













According to the book I am studying (Royden & Fitzpatrick):




We can infer from Zorn's Lemma that every linear space possesses a Hamel basis.




A Hamel Basis is defined as a subset $mathcalB $ of a linear space $X$ provided each vector in $X$ is expressible as a unique $bffinite$ linear combination of vectors in $mathcalB$.



When I first read about the concept of Hamel bases (compared to other sets referred to as basis), I recognized that bases of finite spaces are Hamel basis, and that, for example, $x^k_k=0^infty$ is a Hamel basis of $mathbbR[x]$, the infinite-dimensional space of polynomials with real coefficients.



As comments have pointed out, there might not be a Hamel basis that is explicit to state for other common infinite-dimensional linear spaces ($ell^p$ or $L^p$) - their Hamel bases would need to be uncountable.



However, even if we cannot explicitly characterize the whole basis, could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'? (For example, include $ x^k_k=0^infty$ in the Hamel basis for $L^p([a,b])$). If so, what are the applications of this fact?









share|cite|improve this question












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edited Jul 29 at 7:43









Asaf Karagila

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asked Jul 29 at 5:23









ertl

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  • 1




    When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
    – i707107
    Jul 29 at 5:32










  • Possible duplicate of A Hamel basis for $ell^p$?
    – adfriedman
    Jul 29 at 6:02










  • Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
    – ertl
    Jul 29 at 6:26










  • Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
    – mechanodroid
    Jul 29 at 12:38













  • 1




    When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
    – i707107
    Jul 29 at 5:32










  • Possible duplicate of A Hamel basis for $ell^p$?
    – adfriedman
    Jul 29 at 6:02










  • Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
    – ertl
    Jul 29 at 6:26










  • Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
    – mechanodroid
    Jul 29 at 12:38








1




1




When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
– i707107
Jul 29 at 5:32




When the dimension is continuum, I think there is almost no hope for writing such explicit basis. Choice of one that includes a specific countable linearly independent set is possible though.
– i707107
Jul 29 at 5:32












Possible duplicate of A Hamel basis for $ell^p$?
– adfriedman
Jul 29 at 6:02




Possible duplicate of A Hamel basis for $ell^p$?
– adfriedman
Jul 29 at 6:02












Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
– ertl
Jul 29 at 6:26




Thank you for the link! I changed the question to ask what (if any) 'benefits' there might be to being able to choose a Hamel basis including a certain linearly independent set of vectors. This is not a duplicate as far as I can tell.
– ertl
Jul 29 at 6:26












Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
– mechanodroid
Jul 29 at 12:38





Yes, an arbitrary linearly independent subset $S$ can be extended to a Hamel basis. Just apply Zorn's lemma to the family of all linearly independent sets which contain $S$, ordered by inclusion. The maximal element will be a Hamel basis.
– mechanodroid
Jul 29 at 12:38











1 Answer
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could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'?




Yes, we can.




If so, what are the applications of this fact?




None.






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  • 1




    Care to explain the "None"?
    – T_M
    Jul 29 at 15:26






  • 1




    I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
    – Rhys Steele
    Aug 1 at 20:20











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active

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up vote
0
down vote














could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'?




Yes, we can.




If so, what are the applications of this fact?




None.






share|cite|improve this answer

















  • 1




    Care to explain the "None"?
    – T_M
    Jul 29 at 15:26






  • 1




    I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
    – Rhys Steele
    Aug 1 at 20:20















up vote
0
down vote














could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'?




Yes, we can.




If so, what are the applications of this fact?




None.






share|cite|improve this answer

















  • 1




    Care to explain the "None"?
    – T_M
    Jul 29 at 15:26






  • 1




    I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
    – Rhys Steele
    Aug 1 at 20:20













up vote
0
down vote










up vote
0
down vote










could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'?




Yes, we can.




If so, what are the applications of this fact?




None.






share|cite|improve this answer














could we choose one that includes a specific (countable) set of vectors as a subset, given they are 'independent'?




Yes, we can.




If so, what are the applications of this fact?




None.







share|cite|improve this answer













share|cite|improve this answer



share|cite|improve this answer











answered Jul 29 at 15:18









user357151

13.8k31140




13.8k31140







  • 1




    Care to explain the "None"?
    – T_M
    Jul 29 at 15:26






  • 1




    I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
    – Rhys Steele
    Aug 1 at 20:20













  • 1




    Care to explain the "None"?
    – T_M
    Jul 29 at 15:26






  • 1




    I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
    – Rhys Steele
    Aug 1 at 20:20








1




1




Care to explain the "None"?
– T_M
Jul 29 at 15:26




Care to explain the "None"?
– T_M
Jul 29 at 15:26




1




1




I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
– Rhys Steele
Aug 1 at 20:20





I think "none" is at least an exaggeration, if not just false. For example, a simple application of the fact that we can always extend a linearly independent set to a basis (assuming AC) is the existence of a discontinuous linear functional on any infinite dimensional normed space.
– Rhys Steele
Aug 1 at 20:20













 

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