An identity related to antipode of a Hopf algebra












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Let $H$ be a Hopf algebra with a bijective antipode $S$. Does the equality $sumlimits_{(h)} h_2 otimes S^{-1}(h_1) = sumlimits_{(h)} h_1 otimes S(h_2)$ hold for any $h in H$, where $Delta(h)=sum h_1 otimes h_2$? Thank you.










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    – Vee Hua Zhi
    Dec 19 '18 at 9:47










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    I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
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    – 1985
    Dec 20 '18 at 5:24


















1












$begingroup$


Let $H$ be a Hopf algebra with a bijective antipode $S$. Does the equality $sumlimits_{(h)} h_2 otimes S^{-1}(h_1) = sumlimits_{(h)} h_1 otimes S(h_2)$ hold for any $h in H$, where $Delta(h)=sum h_1 otimes h_2$? Thank you.










share|cite|improve this question









$endgroup$












  • $begingroup$
    Welcome to MSE! It is more likely that you'll receive an answer if you showed us that you've made an effort.
    $endgroup$
    – Vee Hua Zhi
    Dec 19 '18 at 9:47










  • $begingroup$
    I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
    $endgroup$
    – 1985
    Dec 20 '18 at 5:24
















1












1








1





$begingroup$


Let $H$ be a Hopf algebra with a bijective antipode $S$. Does the equality $sumlimits_{(h)} h_2 otimes S^{-1}(h_1) = sumlimits_{(h)} h_1 otimes S(h_2)$ hold for any $h in H$, where $Delta(h)=sum h_1 otimes h_2$? Thank you.










share|cite|improve this question









$endgroup$




Let $H$ be a Hopf algebra with a bijective antipode $S$. Does the equality $sumlimits_{(h)} h_2 otimes S^{-1}(h_1) = sumlimits_{(h)} h_1 otimes S(h_2)$ hold for any $h in H$, where $Delta(h)=sum h_1 otimes h_2$? Thank you.







hopf-algebras






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asked Dec 19 '18 at 9:25









19851985

63




63












  • $begingroup$
    Welcome to MSE! It is more likely that you'll receive an answer if you showed us that you've made an effort.
    $endgroup$
    – Vee Hua Zhi
    Dec 19 '18 at 9:47










  • $begingroup$
    I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
    $endgroup$
    – 1985
    Dec 20 '18 at 5:24




















  • $begingroup$
    Welcome to MSE! It is more likely that you'll receive an answer if you showed us that you've made an effort.
    $endgroup$
    – Vee Hua Zhi
    Dec 19 '18 at 9:47










  • $begingroup$
    I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
    $endgroup$
    – 1985
    Dec 20 '18 at 5:24


















$begingroup$
Welcome to MSE! It is more likely that you'll receive an answer if you showed us that you've made an effort.
$endgroup$
– Vee Hua Zhi
Dec 19 '18 at 9:47




$begingroup$
Welcome to MSE! It is more likely that you'll receive an answer if you showed us that you've made an effort.
$endgroup$
– Vee Hua Zhi
Dec 19 '18 at 9:47












$begingroup$
I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
$endgroup$
– 1985
Dec 20 '18 at 5:24






$begingroup$
I could prove the equality for cocommutative Hopf algebras. As in that case $sum h_2 otimes S^{-1}(h_1) =sum h_1 otimes S^{-1}(h_2)=sum h_1 otimes S(h_2)$. But I do not know in general.
$endgroup$
– 1985
Dec 20 '18 at 5:24












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Observe that your requirement is equivalent to the following
$$Delta= (S^2otimes mathrm{id})circtaucirc Delta,$$
where $tau$ is the flip map.



For a cocommutative Hopf algebra it is known that $S^2=mathrm{id}$, therefore in that case it is true.



In general, consider the Sweedler's Hopf algebra as an counterexample.






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    1 Answer
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    $begingroup$

    Observe that your requirement is equivalent to the following
    $$Delta= (S^2otimes mathrm{id})circtaucirc Delta,$$
    where $tau$ is the flip map.



    For a cocommutative Hopf algebra it is known that $S^2=mathrm{id}$, therefore in that case it is true.



    In general, consider the Sweedler's Hopf algebra as an counterexample.






    share|cite|improve this answer









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      0












      $begingroup$

      Observe that your requirement is equivalent to the following
      $$Delta= (S^2otimes mathrm{id})circtaucirc Delta,$$
      where $tau$ is the flip map.



      For a cocommutative Hopf algebra it is known that $S^2=mathrm{id}$, therefore in that case it is true.



      In general, consider the Sweedler's Hopf algebra as an counterexample.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        Observe that your requirement is equivalent to the following
        $$Delta= (S^2otimes mathrm{id})circtaucirc Delta,$$
        where $tau$ is the flip map.



        For a cocommutative Hopf algebra it is known that $S^2=mathrm{id}$, therefore in that case it is true.



        In general, consider the Sweedler's Hopf algebra as an counterexample.






        share|cite|improve this answer









        $endgroup$



        Observe that your requirement is equivalent to the following
        $$Delta= (S^2otimes mathrm{id})circtaucirc Delta,$$
        where $tau$ is the flip map.



        For a cocommutative Hopf algebra it is known that $S^2=mathrm{id}$, therefore in that case it is true.



        In general, consider the Sweedler's Hopf algebra as an counterexample.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 12 at 19:04









        mikismikis

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