Holomorphic bijection from intersection of two circles to a region between two rays












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What is a holomorphic map from the nonempty intersection of two circles with "tip points" $a$ (below) and $b$ (neither of which are included in one another) to the region $A$ between two rays?




Pictue is below:



We want to find map f



Here is my work so far: by translation and rotation we may assume that the tip of $A$ is the origin one of the rays id the positive real axis, while the region is found by counterclockwise rotation. The professor suggested a map of the form $frac{z-a}{z-b}$, but I am not sure why such a map works. Certainly it maps $a$ to $0$ and $b$ to $infty$ but we have no idea where in the region between two rays $b$ gets mapped to. Also, the angle $alpha$ must be mentioned somehow...










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  • The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
    – Maxim
    Nov 26 at 2:56


















0















What is a holomorphic map from the nonempty intersection of two circles with "tip points" $a$ (below) and $b$ (neither of which are included in one another) to the region $A$ between two rays?




Pictue is below:



We want to find map f



Here is my work so far: by translation and rotation we may assume that the tip of $A$ is the origin one of the rays id the positive real axis, while the region is found by counterclockwise rotation. The professor suggested a map of the form $frac{z-a}{z-b}$, but I am not sure why such a map works. Certainly it maps $a$ to $0$ and $b$ to $infty$ but we have no idea where in the region between two rays $b$ gets mapped to. Also, the angle $alpha$ must be mentioned somehow...










share|cite|improve this question






















  • The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
    – Maxim
    Nov 26 at 2:56
















0












0








0








What is a holomorphic map from the nonempty intersection of two circles with "tip points" $a$ (below) and $b$ (neither of which are included in one another) to the region $A$ between two rays?




Pictue is below:



We want to find map f



Here is my work so far: by translation and rotation we may assume that the tip of $A$ is the origin one of the rays id the positive real axis, while the region is found by counterclockwise rotation. The professor suggested a map of the form $frac{z-a}{z-b}$, but I am not sure why such a map works. Certainly it maps $a$ to $0$ and $b$ to $infty$ but we have no idea where in the region between two rays $b$ gets mapped to. Also, the angle $alpha$ must be mentioned somehow...










share|cite|improve this question














What is a holomorphic map from the nonempty intersection of two circles with "tip points" $a$ (below) and $b$ (neither of which are included in one another) to the region $A$ between two rays?




Pictue is below:



We want to find map f



Here is my work so far: by translation and rotation we may assume that the tip of $A$ is the origin one of the rays id the positive real axis, while the region is found by counterclockwise rotation. The professor suggested a map of the form $frac{z-a}{z-b}$, but I am not sure why such a map works. Certainly it maps $a$ to $0$ and $b$ to $infty$ but we have no idea where in the region between two rays $b$ gets mapped to. Also, the angle $alpha$ must be mentioned somehow...







complex-analysis geometry analytic-geometry mobius-transformation






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asked Nov 22 at 22:01









Cute Brownie

995416




995416












  • The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
    – Maxim
    Nov 26 at 2:56




















  • The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
    – Maxim
    Nov 26 at 2:56


















The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
– Maxim
Nov 26 at 2:56






The map works because the two circles are mapped to two generalized circles that have two common points $0$ and $infty$, that is, two straight lines through the origin. All such Mobius transformations will have the form either $k (z - a)/(z - b)$ or $k (z - b)/(z - a)$, with arbitrary $k neq 0$. The angle $A$ is the same as the angle between the circles. Varying $arg k$ rotates the sector around the origin.
– Maxim
Nov 26 at 2:56

















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