Uniqueness of the basis for a tensor product of vector spaces.

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Having in mind the following answered question:



Tensor Product of Spaces has Basis of Tensor Products



about bases for a tensor product of vector spaces I wonder if that is the only way to get a basis for that tensor other than the obvious. That is, the basis $(e_1)otimes(e_2)$ for $V_1otimesV_2$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2$.



In case it was not unique, would that mean a different tensor product between the corresponding matrices than the usual Kronecker product between matrices?







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  • Bases are never unique.
    – Paul Frost
    Jul 24 at 8:15














up vote
0
down vote

favorite












Having in mind the following answered question:



Tensor Product of Spaces has Basis of Tensor Products



about bases for a tensor product of vector spaces I wonder if that is the only way to get a basis for that tensor other than the obvious. That is, the basis $(e_1)otimes(e_2)$ for $V_1otimesV_2$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2$.



In case it was not unique, would that mean a different tensor product between the corresponding matrices than the usual Kronecker product between matrices?







share|cite|improve this question



















  • Bases are never unique.
    – Paul Frost
    Jul 24 at 8:15












up vote
0
down vote

favorite









up vote
0
down vote

favorite











Having in mind the following answered question:



Tensor Product of Spaces has Basis of Tensor Products



about bases for a tensor product of vector spaces I wonder if that is the only way to get a basis for that tensor other than the obvious. That is, the basis $(e_1)otimes(e_2)$ for $V_1otimesV_2$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2$.



In case it was not unique, would that mean a different tensor product between the corresponding matrices than the usual Kronecker product between matrices?







share|cite|improve this question











Having in mind the following answered question:



Tensor Product of Spaces has Basis of Tensor Products



about bases for a tensor product of vector spaces I wonder if that is the only way to get a basis for that tensor other than the obvious. That is, the basis $(e_1)otimes(e_2)$ for $V_1otimesV_2$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2$.



In case it was not unique, would that mean a different tensor product between the corresponding matrices than the usual Kronecker product between matrices?









share|cite|improve this question










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asked Jul 24 at 6:50









gibarian

5610




5610











  • Bases are never unique.
    – Paul Frost
    Jul 24 at 8:15
















  • Bases are never unique.
    – Paul Frost
    Jul 24 at 8:15















Bases are never unique.
– Paul Frost
Jul 24 at 8:15




Bases are never unique.
– Paul Frost
Jul 24 at 8:15










1 Answer
1






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That is certainly not unique.



To begin with, there are many basis for both $V_1$ and $V_2$ so there are several choices of basis on the form $(e_1) otimes (e_2)$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2.$



Then, one can have "cross-bases". For example, assume that $V_1$ and $V_2$ are both 2-dimensional with bases $ e_1^(1), e_1^(2) $ and $ e_2^(1), e_2^(2) $ respectively. Then as a basis for $V_1 otimes V_2$ you can take
$$
e_1^(1) otimes e_2^(1) + e_1^(1) otimes e_2^(1),
e_1^(1) otimes e_2^(2) + e_1^(1) otimes e_2^(2), \
e_1^(2) otimes e_2^(1) + e_1^(2) otimes e_2^(1),
e_1^(2) otimes e_2^(2) + e_1^(2) otimes e_2^(2)
$$
It isn't certain that you can rewrite any of these basis vectors as a simple tensor product.



Maybe you have heard of quantum entanglement. The mathematical description of these consists of this kind of sums of simple tensor products. See for example these states.






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    1 Answer
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    That is certainly not unique.



    To begin with, there are many basis for both $V_1$ and $V_2$ so there are several choices of basis on the form $(e_1) otimes (e_2)$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2.$



    Then, one can have "cross-bases". For example, assume that $V_1$ and $V_2$ are both 2-dimensional with bases $ e_1^(1), e_1^(2) $ and $ e_2^(1), e_2^(2) $ respectively. Then as a basis for $V_1 otimes V_2$ you can take
    $$
    e_1^(1) otimes e_2^(1) + e_1^(1) otimes e_2^(1),
    e_1^(1) otimes e_2^(2) + e_1^(1) otimes e_2^(2), \
    e_1^(2) otimes e_2^(1) + e_1^(2) otimes e_2^(1),
    e_1^(2) otimes e_2^(2) + e_1^(2) otimes e_2^(2)
    $$
    It isn't certain that you can rewrite any of these basis vectors as a simple tensor product.



    Maybe you have heard of quantum entanglement. The mathematical description of these consists of this kind of sums of simple tensor products. See for example these states.






    share|cite|improve this answer

























      up vote
      0
      down vote













      That is certainly not unique.



      To begin with, there are many basis for both $V_1$ and $V_2$ so there are several choices of basis on the form $(e_1) otimes (e_2)$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2.$



      Then, one can have "cross-bases". For example, assume that $V_1$ and $V_2$ are both 2-dimensional with bases $ e_1^(1), e_1^(2) $ and $ e_2^(1), e_2^(2) $ respectively. Then as a basis for $V_1 otimes V_2$ you can take
      $$
      e_1^(1) otimes e_2^(1) + e_1^(1) otimes e_2^(1),
      e_1^(1) otimes e_2^(2) + e_1^(1) otimes e_2^(2), \
      e_1^(2) otimes e_2^(1) + e_1^(2) otimes e_2^(1),
      e_1^(2) otimes e_2^(2) + e_1^(2) otimes e_2^(2)
      $$
      It isn't certain that you can rewrite any of these basis vectors as a simple tensor product.



      Maybe you have heard of quantum entanglement. The mathematical description of these consists of this kind of sums of simple tensor products. See for example these states.






      share|cite|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        That is certainly not unique.



        To begin with, there are many basis for both $V_1$ and $V_2$ so there are several choices of basis on the form $(e_1) otimes (e_2)$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2.$



        Then, one can have "cross-bases". For example, assume that $V_1$ and $V_2$ are both 2-dimensional with bases $ e_1^(1), e_1^(2) $ and $ e_2^(1), e_2^(2) $ respectively. Then as a basis for $V_1 otimes V_2$ you can take
        $$
        e_1^(1) otimes e_2^(1) + e_1^(1) otimes e_2^(1),
        e_1^(1) otimes e_2^(2) + e_1^(1) otimes e_2^(2), \
        e_1^(2) otimes e_2^(1) + e_1^(2) otimes e_2^(1),
        e_1^(2) otimes e_2^(2) + e_1^(2) otimes e_2^(2)
        $$
        It isn't certain that you can rewrite any of these basis vectors as a simple tensor product.



        Maybe you have heard of quantum entanglement. The mathematical description of these consists of this kind of sums of simple tensor products. See for example these states.






        share|cite|improve this answer













        That is certainly not unique.



        To begin with, there are many basis for both $V_1$ and $V_2$ so there are several choices of basis on the form $(e_1) otimes (e_2)$ where $(e_1)$ is a basis for $V_1$ and $(e_2)$ for $V_2.$



        Then, one can have "cross-bases". For example, assume that $V_1$ and $V_2$ are both 2-dimensional with bases $ e_1^(1), e_1^(2) $ and $ e_2^(1), e_2^(2) $ respectively. Then as a basis for $V_1 otimes V_2$ you can take
        $$
        e_1^(1) otimes e_2^(1) + e_1^(1) otimes e_2^(1),
        e_1^(1) otimes e_2^(2) + e_1^(1) otimes e_2^(2), \
        e_1^(2) otimes e_2^(1) + e_1^(2) otimes e_2^(1),
        e_1^(2) otimes e_2^(2) + e_1^(2) otimes e_2^(2)
        $$
        It isn't certain that you can rewrite any of these basis vectors as a simple tensor product.



        Maybe you have heard of quantum entanglement. The mathematical description of these consists of this kind of sums of simple tensor products. See for example these states.







        share|cite|improve this answer













        share|cite|improve this answer



        share|cite|improve this answer











        answered Jul 24 at 8:17









        md2perpe

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