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Magnifying glass in hyperbolic space


Is it possible to deduce a model for hyperbolic geometry from a synthetic set of axioms a la Euclid/Hilbert/Tarski?Symbolic coordinates for a hyperbolic grid?Hyperbolic (and related) structures on open unit diskWhat is the volume of the sphere in hyperbolic space?Non-equivalent metrics on $PSL_2(mathbbR)$Is there a relationship between the Cantor set and hyperbolic geometry?Translation in Poincare disc modelProve that a loxodromic transformation has an attractor and a repeller as fixed pointsSpheres in hyperbolic spacesExplicit isomorphisms between the hyperbolic plane and surfaces of constant negative curvature













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My grandmother used to read with a magnifying glass. What (an ideal) magnifying glass does, is basically a homothety: it scales the picture by some factor. Now, in a hyperbolic space there is no such thing as homothety. So, what a person living in a hyperbolic space would do to improve poor vision?










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    7












    $begingroup$


    My grandmother used to read with a magnifying glass. What (an ideal) magnifying glass does, is basically a homothety: it scales the picture by some factor. Now, in a hyperbolic space there is no such thing as homothety. So, what a person living in a hyperbolic space would do to improve poor vision?










    share|cite|improve this question









    $endgroup$














      7












      7








      7





      $begingroup$


      My grandmother used to read with a magnifying glass. What (an ideal) magnifying glass does, is basically a homothety: it scales the picture by some factor. Now, in a hyperbolic space there is no such thing as homothety. So, what a person living in a hyperbolic space would do to improve poor vision?










      share|cite|improve this question









      $endgroup$




      My grandmother used to read with a magnifying glass. What (an ideal) magnifying glass does, is basically a homothety: it scales the picture by some factor. Now, in a hyperbolic space there is no such thing as homothety. So, what a person living in a hyperbolic space would do to improve poor vision?







      geometry hyperbolic-geometry






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      share|cite|improve this question











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      share|cite|improve this question










      asked 2 hours ago









      liaombroliaombro

      32428




      32428




















          1 Answer
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          $begingroup$

          What you say will still be true: a magnifying glass will still scale the picture by some factor. Let us say that the scale factor is $ell > 1$.



          The difference will be that the scaled picture will no longer be a picture of the old familiar hyperbolic space in which the sectional curvature is $-1$. Instead, it will be a picture of hyperbolic space with curvature $-frac1ell^2$; I'm using here that the units of curvature are basically $1/text(length)^2$.



          So, for example, a really powerful magnifying glass with scale factor $ell >!!> 1$ will present a picture of a hyperbolic space whose curvature is nearly zero, being pretty much indistinguishable from Euclidean space.






          share|cite|improve this answer









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            $begingroup$

            What you say will still be true: a magnifying glass will still scale the picture by some factor. Let us say that the scale factor is $ell > 1$.



            The difference will be that the scaled picture will no longer be a picture of the old familiar hyperbolic space in which the sectional curvature is $-1$. Instead, it will be a picture of hyperbolic space with curvature $-frac1ell^2$; I'm using here that the units of curvature are basically $1/text(length)^2$.



            So, for example, a really powerful magnifying glass with scale factor $ell >!!> 1$ will present a picture of a hyperbolic space whose curvature is nearly zero, being pretty much indistinguishable from Euclidean space.






            share|cite|improve this answer









            $endgroup$

















              5












              $begingroup$

              What you say will still be true: a magnifying glass will still scale the picture by some factor. Let us say that the scale factor is $ell > 1$.



              The difference will be that the scaled picture will no longer be a picture of the old familiar hyperbolic space in which the sectional curvature is $-1$. Instead, it will be a picture of hyperbolic space with curvature $-frac1ell^2$; I'm using here that the units of curvature are basically $1/text(length)^2$.



              So, for example, a really powerful magnifying glass with scale factor $ell >!!> 1$ will present a picture of a hyperbolic space whose curvature is nearly zero, being pretty much indistinguishable from Euclidean space.






              share|cite|improve this answer









              $endgroup$















                5












                5








                5





                $begingroup$

                What you say will still be true: a magnifying glass will still scale the picture by some factor. Let us say that the scale factor is $ell > 1$.



                The difference will be that the scaled picture will no longer be a picture of the old familiar hyperbolic space in which the sectional curvature is $-1$. Instead, it will be a picture of hyperbolic space with curvature $-frac1ell^2$; I'm using here that the units of curvature are basically $1/text(length)^2$.



                So, for example, a really powerful magnifying glass with scale factor $ell >!!> 1$ will present a picture of a hyperbolic space whose curvature is nearly zero, being pretty much indistinguishable from Euclidean space.






                share|cite|improve this answer









                $endgroup$



                What you say will still be true: a magnifying glass will still scale the picture by some factor. Let us say that the scale factor is $ell > 1$.



                The difference will be that the scaled picture will no longer be a picture of the old familiar hyperbolic space in which the sectional curvature is $-1$. Instead, it will be a picture of hyperbolic space with curvature $-frac1ell^2$; I'm using here that the units of curvature are basically $1/text(length)^2$.



                So, for example, a really powerful magnifying glass with scale factor $ell >!!> 1$ will present a picture of a hyperbolic space whose curvature is nearly zero, being pretty much indistinguishable from Euclidean space.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered 2 hours ago









                Lee MosherLee Mosher

                50.8k33787




                50.8k33787



























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