Geometry as a Group Action












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At 38:45 in this lecture by Thurston he defines a geometry as a an action by a group $G$ on a simply connected topological space $X$ such that the action is transitive and the stabilizer of a point $xin X$ is compact. How would you construct Euclidean and or spherical geometry using Thurston's definition?










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$endgroup$








  • 2




    $begingroup$
    I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
    $endgroup$
    – Charlie Frohman
    Jan 29 at 2:22












  • $begingroup$
    @CharlieFrohman OK thanks. I'll take a look.
    $endgroup$
    – Bob
    Jan 29 at 18:47












  • $begingroup$
    @CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
    $endgroup$
    – Bob
    Feb 7 at 18:39










  • $begingroup$
    Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:05










  • $begingroup$
    Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:11
















3












$begingroup$


At 38:45 in this lecture by Thurston he defines a geometry as a an action by a group $G$ on a simply connected topological space $X$ such that the action is transitive and the stabilizer of a point $xin X$ is compact. How would you construct Euclidean and or spherical geometry using Thurston's definition?










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
    $endgroup$
    – Charlie Frohman
    Jan 29 at 2:22












  • $begingroup$
    @CharlieFrohman OK thanks. I'll take a look.
    $endgroup$
    – Bob
    Jan 29 at 18:47












  • $begingroup$
    @CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
    $endgroup$
    – Bob
    Feb 7 at 18:39










  • $begingroup$
    Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:05










  • $begingroup$
    Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:11














3












3








3





$begingroup$


At 38:45 in this lecture by Thurston he defines a geometry as a an action by a group $G$ on a simply connected topological space $X$ such that the action is transitive and the stabilizer of a point $xin X$ is compact. How would you construct Euclidean and or spherical geometry using Thurston's definition?










share|cite|improve this question









$endgroup$




At 38:45 in this lecture by Thurston he defines a geometry as a an action by a group $G$ on a simply connected topological space $X$ such that the action is transitive and the stabilizer of a point $xin X$ is compact. How would you construct Euclidean and or spherical geometry using Thurston's definition?







group-theory manifolds low-dimensional-topology






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 28 at 23:56









BobBob

684410




684410








  • 2




    $begingroup$
    I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
    $endgroup$
    – Charlie Frohman
    Jan 29 at 2:22












  • $begingroup$
    @CharlieFrohman OK thanks. I'll take a look.
    $endgroup$
    – Bob
    Jan 29 at 18:47












  • $begingroup$
    @CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
    $endgroup$
    – Bob
    Feb 7 at 18:39










  • $begingroup$
    Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:05










  • $begingroup$
    Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:11














  • 2




    $begingroup$
    I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
    $endgroup$
    – Charlie Frohman
    Jan 29 at 2:22












  • $begingroup$
    @CharlieFrohman OK thanks. I'll take a look.
    $endgroup$
    – Bob
    Jan 29 at 18:47












  • $begingroup$
    @CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
    $endgroup$
    – Bob
    Feb 7 at 18:39










  • $begingroup$
    Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:05










  • $begingroup$
    Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
    $endgroup$
    – Charlie Frohman
    Feb 7 at 22:11








2




2




$begingroup$
I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
$endgroup$
– Charlie Frohman
Jan 29 at 2:22






$begingroup$
I think you left out analytic. For Euclidean, $X$ is the plane and $G$ is the group of congruence transformations. For spherical, $X$ is the two-sphere $G$ is $SO(3)$. Read his notes, you can download them from MSRI.
$endgroup$
– Charlie Frohman
Jan 29 at 2:22














$begingroup$
@CharlieFrohman OK thanks. I'll take a look.
$endgroup$
– Bob
Jan 29 at 18:47






$begingroup$
@CharlieFrohman OK thanks. I'll take a look.
$endgroup$
– Bob
Jan 29 at 18:47














$begingroup$
@CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
$endgroup$
– Bob
Feb 7 at 18:39




$begingroup$
@CharlieFrohman In what branch of mathematics would they introduce the definition of a geometry in this way? I'd like to get a good book on the subject.
$endgroup$
– Bob
Feb 7 at 18:39












$begingroup$
Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
$endgroup$
– Charlie Frohman
Feb 7 at 22:05




$begingroup$
Low dimensional topology. You can download Thurston’s notes from MSRI. The approach goes back to the 19th century. The section with this definition is: library.msri.org/books/gt3m/PDF/3.pdf
$endgroup$
– Charlie Frohman
Feb 7 at 22:05












$begingroup$
Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
$endgroup$
– Charlie Frohman
Feb 7 at 22:11




$begingroup$
Here is an undergraduate introduction: Low-Dimensional Geometry (Student Mathematical Library: IAS/Park City Mathematical Subseries) amazon.com/dp/082184816X/ref=cm_sw_r_cp_api_i_-YkxCbJ7WQR22
$endgroup$
– Charlie Frohman
Feb 7 at 22:11










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