Submanifold of real projective space












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Would you like to tell me how to prove that ${[x_{0}:x_{1}:x_{2}]: x_{0}x_{1} + x_{2}^{2} = 0 } subset mathbb{R}mathbb{P}^{2}$ is a submanifold (of $mathbb{R}mathbb{P}^{2}$)?










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    $begingroup$


    Would you like to tell me how to prove that ${[x_{0}:x_{1}:x_{2}]: x_{0}x_{1} + x_{2}^{2} = 0 } subset mathbb{R}mathbb{P}^{2}$ is a submanifold (of $mathbb{R}mathbb{P}^{2}$)?










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      $begingroup$


      Would you like to tell me how to prove that ${[x_{0}:x_{1}:x_{2}]: x_{0}x_{1} + x_{2}^{2} = 0 } subset mathbb{R}mathbb{P}^{2}$ is a submanifold (of $mathbb{R}mathbb{P}^{2}$)?










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      Would you like to tell me how to prove that ${[x_{0}:x_{1}:x_{2}]: x_{0}x_{1} + x_{2}^{2} = 0 } subset mathbb{R}mathbb{P}^{2}$ is a submanifold (of $mathbb{R}mathbb{P}^{2}$)?







      differential-geometry differential-topology projective-space






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      edited Dec 13 '18 at 8:39







      kNiEsSoKk

















      asked Dec 12 '18 at 14:09









      kNiEsSoKkkNiEsSoKk

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          $begingroup$

          I believe you want to say $x_0x_1+x_2^2=0$. Let $V$ be that subset. Consider $U_0={[x_0,x_1,x_2],x_0neq 0}$ define $f([x_0,x_1,x_2])={x_1over x_0}+{x_2^2over x_0^2}$ is a submersion on $U_0$ this shows that $Vcap U_0$ is a submanifold.






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          • $begingroup$
            Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
            $endgroup$
            – kNiEsSoKk
            Dec 13 '18 at 9:56













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          $begingroup$

          I believe you want to say $x_0x_1+x_2^2=0$. Let $V$ be that subset. Consider $U_0={[x_0,x_1,x_2],x_0neq 0}$ define $f([x_0,x_1,x_2])={x_1over x_0}+{x_2^2over x_0^2}$ is a submersion on $U_0$ this shows that $Vcap U_0$ is a submanifold.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
            $endgroup$
            – kNiEsSoKk
            Dec 13 '18 at 9:56


















          1












          $begingroup$

          I believe you want to say $x_0x_1+x_2^2=0$. Let $V$ be that subset. Consider $U_0={[x_0,x_1,x_2],x_0neq 0}$ define $f([x_0,x_1,x_2])={x_1over x_0}+{x_2^2over x_0^2}$ is a submersion on $U_0$ this shows that $Vcap U_0$ is a submanifold.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
            $endgroup$
            – kNiEsSoKk
            Dec 13 '18 at 9:56
















          1












          1








          1





          $begingroup$

          I believe you want to say $x_0x_1+x_2^2=0$. Let $V$ be that subset. Consider $U_0={[x_0,x_1,x_2],x_0neq 0}$ define $f([x_0,x_1,x_2])={x_1over x_0}+{x_2^2over x_0^2}$ is a submersion on $U_0$ this shows that $Vcap U_0$ is a submanifold.






          share|cite|improve this answer









          $endgroup$



          I believe you want to say $x_0x_1+x_2^2=0$. Let $V$ be that subset. Consider $U_0={[x_0,x_1,x_2],x_0neq 0}$ define $f([x_0,x_1,x_2])={x_1over x_0}+{x_2^2over x_0^2}$ is a submersion on $U_0$ this shows that $Vcap U_0$ is a submanifold.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 12 '18 at 15:28









          Tsemo AristideTsemo Aristide

          58.7k11445




          58.7k11445












          • $begingroup$
            Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
            $endgroup$
            – kNiEsSoKk
            Dec 13 '18 at 9:56




















          • $begingroup$
            Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
            $endgroup$
            – kNiEsSoKk
            Dec 13 '18 at 9:56


















          $begingroup$
          Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
          $endgroup$
          – kNiEsSoKk
          Dec 13 '18 at 9:56






          $begingroup$
          Thanks! I found the proposition $f:mathbb{R}mathbb{P}^{2} rightarrow mathbb{R}$ smooth and $qinmathbb{R}$ a regular value $implies f^{-1}(q)$ is a submanifold of $mathbb{R}mathbb{P}^{2}$. Is this what you are using?
          $endgroup$
          – kNiEsSoKk
          Dec 13 '18 at 9:56




















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