Prove that a star-shaped open set is simply connected with diffierent definition of simple connected .












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Prove that a star-shaped open set is simply connected.




This is an exercise in Stein's complex analysis and I have already seen one of the proof here.

In Stein's book , A region $Omega$ in the complex plane is simply connected if any two pair of curves in $Omega$ with the same end-points are homotopic. But in the proof above , it seems to apply another definition of simply connected (any closed curve in the region is homotopic to a point in the region?) .

My question:

a) How to prove this exercise with the definition of simple connected in Stein's book .

b) What kind of the definition of simple connected did the proof above applied . Are the two definition of simple connected the same ? If so , how to show this ?










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$endgroup$

















    1












    $begingroup$



    Prove that a star-shaped open set is simply connected.




    This is an exercise in Stein's complex analysis and I have already seen one of the proof here.

    In Stein's book , A region $Omega$ in the complex plane is simply connected if any two pair of curves in $Omega$ with the same end-points are homotopic. But in the proof above , it seems to apply another definition of simply connected (any closed curve in the region is homotopic to a point in the region?) .

    My question:

    a) How to prove this exercise with the definition of simple connected in Stein's book .

    b) What kind of the definition of simple connected did the proof above applied . Are the two definition of simple connected the same ? If so , how to show this ?










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$



      Prove that a star-shaped open set is simply connected.




      This is an exercise in Stein's complex analysis and I have already seen one of the proof here.

      In Stein's book , A region $Omega$ in the complex plane is simply connected if any two pair of curves in $Omega$ with the same end-points are homotopic. But in the proof above , it seems to apply another definition of simply connected (any closed curve in the region is homotopic to a point in the region?) .

      My question:

      a) How to prove this exercise with the definition of simple connected in Stein's book .

      b) What kind of the definition of simple connected did the proof above applied . Are the two definition of simple connected the same ? If so , how to show this ?










      share|cite|improve this question









      $endgroup$





      Prove that a star-shaped open set is simply connected.




      This is an exercise in Stein's complex analysis and I have already seen one of the proof here.

      In Stein's book , A region $Omega$ in the complex plane is simply connected if any two pair of curves in $Omega$ with the same end-points are homotopic. But in the proof above , it seems to apply another definition of simply connected (any closed curve in the region is homotopic to a point in the region?) .

      My question:

      a) How to prove this exercise with the definition of simple connected in Stein's book .

      b) What kind of the definition of simple connected did the proof above applied . Are the two definition of simple connected the same ? If so , how to show this ?







      complex-analysis






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      share|cite|improve this question











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      asked Jan 5 at 7:04









      J.GuoJ.Guo

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