What's the name of this vector space?

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For a vector space $V$ and its subspace $W$, there is a vector space $W^perp:= xin V^* $.



If $V$ is a finite dimensional inner product vector space, I think $W^perp$ can be called orthogonal complement of $W$. However, what's the name of this in the general case?







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    up vote
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    down vote

    favorite












    For a vector space $V$ and its subspace $W$, there is a vector space $W^perp:= xin V^* $.



    If $V$ is a finite dimensional inner product vector space, I think $W^perp$ can be called orthogonal complement of $W$. However, what's the name of this in the general case?







    share|cite|improve this question























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      For a vector space $V$ and its subspace $W$, there is a vector space $W^perp:= xin V^* $.



      If $V$ is a finite dimensional inner product vector space, I think $W^perp$ can be called orthogonal complement of $W$. However, what's the name of this in the general case?







      share|cite|improve this question













      For a vector space $V$ and its subspace $W$, there is a vector space $W^perp:= xin V^* $.



      If $V$ is a finite dimensional inner product vector space, I think $W^perp$ can be called orthogonal complement of $W$. However, what's the name of this in the general case?









      share|cite|improve this question












      share|cite|improve this question




      share|cite|improve this question








      edited Jul 23 at 12:47









      Rhys Steele

      5,5751828




      5,5751828









      asked Jul 23 at 12:44









      satoukibi

      16016




      16016




















          1 Answer
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          That's the annihilator of $W$. It applies to any subset of $V$, not just to subspaces.






          share|cite|improve this answer

















          • 3




            Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
            – John Hughes
            Jul 23 at 12:54










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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          2
          down vote



          accepted










          That's the annihilator of $W$. It applies to any subset of $V$, not just to subspaces.






          share|cite|improve this answer

















          • 3




            Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
            – John Hughes
            Jul 23 at 12:54














          up vote
          2
          down vote



          accepted










          That's the annihilator of $W$. It applies to any subset of $V$, not just to subspaces.






          share|cite|improve this answer

















          • 3




            Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
            – John Hughes
            Jul 23 at 12:54












          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          That's the annihilator of $W$. It applies to any subset of $V$, not just to subspaces.






          share|cite|improve this answer













          That's the annihilator of $W$. It applies to any subset of $V$, not just to subspaces.







          share|cite|improve this answer













          share|cite|improve this answer



          share|cite|improve this answer











          answered Jul 23 at 12:48









          José Carlos Santos

          113k1698176




          113k1698176







          • 3




            Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
            – John Hughes
            Jul 23 at 12:54












          • 3




            Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
            – John Hughes
            Jul 23 at 12:54







          3




          3




          Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
          – John Hughes
          Jul 23 at 12:54




          Just to add a little more context: This idea also applies to general vector spaces, $V$, not just those with an inner product. If there is an inner product, and if $W$ is a subspace, then there's a nice isomorphism between the thing OP called $W^perp$ and $W' = u in V mid forall y in W, langle u, vrangle = 0 $, which is what most people mean by "$W^perp$". The isomorphism $W' to W^perp$ is simply $u mapsto (v mapsto langle u, v rangle)$; of course, proving it's an isomorphism takes a little bit of work.
          – John Hughes
          Jul 23 at 12:54












           

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