A problem on path connectedness of unit ball in R*RExtending a continuous function on the unit sphere to the...

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A problem on path connectedness of unit ball in R*R


Extending a continuous function on the unit sphere to the unit ballConvexity implies the equivalence of order and subspace topologiesPath connectedness is a topological invariant?Questions on the counterexample for “connectedness doesn't imply path-connectedness”Compactness of the closed unit ball in the weak* topology: the Banach–Alaoglu theoremExample of Connected but Not-Path Connected SetShow that $T$(contains segments) is path connectedPath connectednessContinuity and path-connectednessLocal connectedness and path-connectedness of a square $Itimes I$.













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$begingroup$


Actually, I am having a problem over the fact that as $f:[0,1]rightarrowmathbb{R}^{2}$ , $f(t)= (1-t)x + ty$ is continuous, $x,yinmathbb{R}^{2}$, then $f([0,1])$ is connected . Then as unit ball in $mathbb{R}^{2}$ is an ordered set in the order topology, by IVP of $f$ any point between $x=(0,1)$ and $y=(1,0)$ must have a pre-image in $[0,1]$ , but by the dictionary order topology, $(0,1)< z=(1/2,5/8) < (1,0)$ , but $z$ has no pre-image under $f$, but $z$ lies in the unit ball . Why ???
I want a clear explanation over this dubiousness .










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$endgroup$












  • $begingroup$
    What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
    $endgroup$
    – Joel Pereira
    Mar 3 at 16:05










  • $begingroup$
    Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
    $endgroup$
    – RABI KUMAR CHAKRABORTY
    Mar 3 at 18:16


















0












$begingroup$


Actually, I am having a problem over the fact that as $f:[0,1]rightarrowmathbb{R}^{2}$ , $f(t)= (1-t)x + ty$ is continuous, $x,yinmathbb{R}^{2}$, then $f([0,1])$ is connected . Then as unit ball in $mathbb{R}^{2}$ is an ordered set in the order topology, by IVP of $f$ any point between $x=(0,1)$ and $y=(1,0)$ must have a pre-image in $[0,1]$ , but by the dictionary order topology, $(0,1)< z=(1/2,5/8) < (1,0)$ , but $z$ has no pre-image under $f$, but $z$ lies in the unit ball . Why ???
I want a clear explanation over this dubiousness .










share|cite|improve this question











$endgroup$












  • $begingroup$
    What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
    $endgroup$
    – Joel Pereira
    Mar 3 at 16:05










  • $begingroup$
    Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
    $endgroup$
    – RABI KUMAR CHAKRABORTY
    Mar 3 at 18:16
















0












0








0





$begingroup$


Actually, I am having a problem over the fact that as $f:[0,1]rightarrowmathbb{R}^{2}$ , $f(t)= (1-t)x + ty$ is continuous, $x,yinmathbb{R}^{2}$, then $f([0,1])$ is connected . Then as unit ball in $mathbb{R}^{2}$ is an ordered set in the order topology, by IVP of $f$ any point between $x=(0,1)$ and $y=(1,0)$ must have a pre-image in $[0,1]$ , but by the dictionary order topology, $(0,1)< z=(1/2,5/8) < (1,0)$ , but $z$ has no pre-image under $f$, but $z$ lies in the unit ball . Why ???
I want a clear explanation over this dubiousness .










share|cite|improve this question











$endgroup$




Actually, I am having a problem over the fact that as $f:[0,1]rightarrowmathbb{R}^{2}$ , $f(t)= (1-t)x + ty$ is continuous, $x,yinmathbb{R}^{2}$, then $f([0,1])$ is connected . Then as unit ball in $mathbb{R}^{2}$ is an ordered set in the order topology, by IVP of $f$ any point between $x=(0,1)$ and $y=(1,0)$ must have a pre-image in $[0,1]$ , but by the dictionary order topology, $(0,1)< z=(1/2,5/8) < (1,0)$ , but $z$ has no pre-image under $f$, but $z$ lies in the unit ball . Why ???
I want a clear explanation over this dubiousness .







general-topology connectedness path-connected






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share|cite|improve this question













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edited 17 hours ago









Robert Thingum

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8931317










asked Mar 3 at 15:48









RABI KUMAR CHAKRABORTYRABI KUMAR CHAKRABORTY

565




565












  • $begingroup$
    What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
    $endgroup$
    – Joel Pereira
    Mar 3 at 16:05










  • $begingroup$
    Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
    $endgroup$
    – RABI KUMAR CHAKRABORTY
    Mar 3 at 18:16




















  • $begingroup$
    What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
    $endgroup$
    – Joel Pereira
    Mar 3 at 16:05










  • $begingroup$
    Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
    $endgroup$
    – RABI KUMAR CHAKRABORTY
    Mar 3 at 18:16


















$begingroup$
What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
$endgroup$
– Joel Pereira
Mar 3 at 16:05




$begingroup$
What is RR? Do you mean $mathbb{R}^2$? The unit ball is path connected, but you have to take paths $on the unit ball$. Think of the intersection of the ball with the plane that contains x, y, and the origin. The intersection is a great circle. The arc of the circle connecting x and y is a path.
$endgroup$
– Joel Pereira
Mar 3 at 16:05












$begingroup$
Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
$endgroup$
– RABI KUMAR CHAKRABORTY
Mar 3 at 18:16






$begingroup$
Yes Joel, I mean R*R, my confusion lies in the fact that when the points of the unit ball are written on a line, then for f(0)=(0,1) and f(1)=(1,0) , then by dictionary order (1/2,5/8) lies in between f(0) and f(1), and it also lies on the unit ball , then by IVP of f, it must have a pre-image in [0,1], where is that ?????
$endgroup$
– RABI KUMAR CHAKRABORTY
Mar 3 at 18:16












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