A connected embedded submanifold, which is contained in an immersed submanifold, is connected in this...












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I'm currently studying foliation theory, and to solve a problem I need the following to be true, but I can't prove nor disprove, I just have a feeling it may be false in general: if I have a smooth manifold $M,$ and a connected embedded submanifold $P$ of $M,$ which is contained in an immersed submanifold $F$ of $M,$ is $P$ also connected in the immersed submanifold topology of $F$?



At first I thought this was obviously true, but giving it a little more thinking, either I'm making some mistake or, if this is true, it is certainly not obvious. Here is what I did: $F$ may have a finer topology than its subspace topology. If $F$ was an embedded manifold, then the subspace topology of $P$ in $M$ would coincide with its the subspace topology as a subset of $F,$and then it would be connected in $F$. But with $F$ being immersed, $P$ with a topology induced by the immersed topology of $F$ may have an open set which messes with its connectedness. Any ideas, or did I made some mistake? Thanks.










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    $begingroup$


    I'm currently studying foliation theory, and to solve a problem I need the following to be true, but I can't prove nor disprove, I just have a feeling it may be false in general: if I have a smooth manifold $M,$ and a connected embedded submanifold $P$ of $M,$ which is contained in an immersed submanifold $F$ of $M,$ is $P$ also connected in the immersed submanifold topology of $F$?



    At first I thought this was obviously true, but giving it a little more thinking, either I'm making some mistake or, if this is true, it is certainly not obvious. Here is what I did: $F$ may have a finer topology than its subspace topology. If $F$ was an embedded manifold, then the subspace topology of $P$ in $M$ would coincide with its the subspace topology as a subset of $F,$and then it would be connected in $F$. But with $F$ being immersed, $P$ with a topology induced by the immersed topology of $F$ may have an open set which messes with its connectedness. Any ideas, or did I made some mistake? Thanks.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I'm currently studying foliation theory, and to solve a problem I need the following to be true, but I can't prove nor disprove, I just have a feeling it may be false in general: if I have a smooth manifold $M,$ and a connected embedded submanifold $P$ of $M,$ which is contained in an immersed submanifold $F$ of $M,$ is $P$ also connected in the immersed submanifold topology of $F$?



      At first I thought this was obviously true, but giving it a little more thinking, either I'm making some mistake or, if this is true, it is certainly not obvious. Here is what I did: $F$ may have a finer topology than its subspace topology. If $F$ was an embedded manifold, then the subspace topology of $P$ in $M$ would coincide with its the subspace topology as a subset of $F,$and then it would be connected in $F$. But with $F$ being immersed, $P$ with a topology induced by the immersed topology of $F$ may have an open set which messes with its connectedness. Any ideas, or did I made some mistake? Thanks.










      share|cite|improve this question











      $endgroup$




      I'm currently studying foliation theory, and to solve a problem I need the following to be true, but I can't prove nor disprove, I just have a feeling it may be false in general: if I have a smooth manifold $M,$ and a connected embedded submanifold $P$ of $M,$ which is contained in an immersed submanifold $F$ of $M,$ is $P$ also connected in the immersed submanifold topology of $F$?



      At first I thought this was obviously true, but giving it a little more thinking, either I'm making some mistake or, if this is true, it is certainly not obvious. Here is what I did: $F$ may have a finer topology than its subspace topology. If $F$ was an embedded manifold, then the subspace topology of $P$ in $M$ would coincide with its the subspace topology as a subset of $F,$and then it would be connected in $F$. But with $F$ being immersed, $P$ with a topology induced by the immersed topology of $F$ may have an open set which messes with its connectedness. Any ideas, or did I made some mistake? Thanks.







      general-topology manifolds connectedness






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      edited Dec 24 '18 at 6:48







      Vic

















      asked Dec 24 '18 at 6:31









      VicVic

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          This is in fact false in general. Let $M=mathbb{R}^2$ and let $F$ be an open interval immersed in $M$ in the shape of the numeral $$mathsf{8},$$ starting from the middle point and going around the top loop counterclockwise and then around the bottom loop clockwise. Let $P$ be a subset of the $mathsf{8}$ which starts at the bottom left and then goes diagonally to the top right. Then $P$ is of course a connected embedded submanifold of $M$. However, $P$ is not connected in the topology of $F$, since it consists of two separate intervals at the start and end of $F$ together with one point (the middle point) which is halfway between them.






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          • $begingroup$
            And the immersed 8 figure saves the day again. Thanks!
            $endgroup$
            – Vic
            Dec 24 '18 at 19:45











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          $begingroup$

          This is in fact false in general. Let $M=mathbb{R}^2$ and let $F$ be an open interval immersed in $M$ in the shape of the numeral $$mathsf{8},$$ starting from the middle point and going around the top loop counterclockwise and then around the bottom loop clockwise. Let $P$ be a subset of the $mathsf{8}$ which starts at the bottom left and then goes diagonally to the top right. Then $P$ is of course a connected embedded submanifold of $M$. However, $P$ is not connected in the topology of $F$, since it consists of two separate intervals at the start and end of $F$ together with one point (the middle point) which is halfway between them.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            And the immersed 8 figure saves the day again. Thanks!
            $endgroup$
            – Vic
            Dec 24 '18 at 19:45
















          2












          $begingroup$

          This is in fact false in general. Let $M=mathbb{R}^2$ and let $F$ be an open interval immersed in $M$ in the shape of the numeral $$mathsf{8},$$ starting from the middle point and going around the top loop counterclockwise and then around the bottom loop clockwise. Let $P$ be a subset of the $mathsf{8}$ which starts at the bottom left and then goes diagonally to the top right. Then $P$ is of course a connected embedded submanifold of $M$. However, $P$ is not connected in the topology of $F$, since it consists of two separate intervals at the start and end of $F$ together with one point (the middle point) which is halfway between them.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            And the immersed 8 figure saves the day again. Thanks!
            $endgroup$
            – Vic
            Dec 24 '18 at 19:45














          2












          2








          2





          $begingroup$

          This is in fact false in general. Let $M=mathbb{R}^2$ and let $F$ be an open interval immersed in $M$ in the shape of the numeral $$mathsf{8},$$ starting from the middle point and going around the top loop counterclockwise and then around the bottom loop clockwise. Let $P$ be a subset of the $mathsf{8}$ which starts at the bottom left and then goes diagonally to the top right. Then $P$ is of course a connected embedded submanifold of $M$. However, $P$ is not connected in the topology of $F$, since it consists of two separate intervals at the start and end of $F$ together with one point (the middle point) which is halfway between them.






          share|cite|improve this answer









          $endgroup$



          This is in fact false in general. Let $M=mathbb{R}^2$ and let $F$ be an open interval immersed in $M$ in the shape of the numeral $$mathsf{8},$$ starting from the middle point and going around the top loop counterclockwise and then around the bottom loop clockwise. Let $P$ be a subset of the $mathsf{8}$ which starts at the bottom left and then goes diagonally to the top right. Then $P$ is of course a connected embedded submanifold of $M$. However, $P$ is not connected in the topology of $F$, since it consists of two separate intervals at the start and end of $F$ together with one point (the middle point) which is halfway between them.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 24 '18 at 7:05









          Eric WofseyEric Wofsey

          189k14216347




          189k14216347












          • $begingroup$
            And the immersed 8 figure saves the day again. Thanks!
            $endgroup$
            – Vic
            Dec 24 '18 at 19:45


















          • $begingroup$
            And the immersed 8 figure saves the day again. Thanks!
            $endgroup$
            – Vic
            Dec 24 '18 at 19:45
















          $begingroup$
          And the immersed 8 figure saves the day again. Thanks!
          $endgroup$
          – Vic
          Dec 24 '18 at 19:45




          $begingroup$
          And the immersed 8 figure saves the day again. Thanks!
          $endgroup$
          – Vic
          Dec 24 '18 at 19:45


















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