If $H$ is a Hopf algebra over a field and $K$ is a a right or left coideal of $H$ then $K^+$ K^+=K\cap\ker\epsilon$ is a coideal of $H$. Does this hold when $k$ is a commutative ring? If not what is a counter example.
Thanks!
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2 | I specialized what I mean for $K^+$. | ||
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Coideals of Hopf algebra coming from right (left) coideals K->K^+If $H$ is a Hopf algebra over a field and $K$ is a a right or left coideal of $H$ then $K^+$ is a coideal of $H$. Does this hold when $k$ is a commutative ring? If not what is a counter example. Thanks!
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