# Projection of a Torus

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 Revision as of 14:38, 7 July 2009 (edit)← Previous diff Current revision (13:10, 29 November 2011) (edit) (undo) (9 intermediate revisions not shown.) Line 1: Line 1: - {{Image Description + {{Image Description Ready - |ImageName=Projection of a 4-Dimensional Torus + |ImageName=4-Dimensional Torus |Image=4dtorus.jpg |Image=4dtorus.jpg - |ImageIntro=A four-dimensional torus projected into three-dimensional space. + |ImageIntro=A torus in four dimensions projected into three-dimensional space. - |ImageDescElem=It is impossible to visualize a complete four-dimensional object, since we have only ever lived in three-dimensional space. However, there are ways to capture parts of the four-dimensional object in three-dimensional space. + |ImageDescElem=It is impossible to visualize an object in four-dimensions, since we have only ever lived in three-dimensional space. However, there are ways to capture features of the four-dimensional object in three-dimensional space. A useful analogy is a world map. We can capture the essence of the three-dimensional globe on a two-dimensional map, but only by using a projection, which translates a three-dimensional object onto a two-dimensional surface at the expense of distorting the object in some way. A useful analogy is a world map. We can capture the essence of the three-dimensional globe on a two-dimensional map, but only by using a projection, which translates a three-dimensional object onto a two-dimensional surface at the expense of distorting the object in some way. - A similar process is carried out to create this page's main image. A four-dimensional object, described further below, is projected into three-dimensions using two different projections. + A similar process is carried out to create this page's main image. An object in four-dimensional space, described further below, is projected into three-dimensions using two different projections. - |ImageDesc=The four-dimensional torus is defined [[Parametric Equations|parametrically]] by $(x_1,\,x_2,\,x_3,\,x_4)=(cos(u),\,sin(u),\,cos(v),\,sin(v))$. The first two coordinates of the parametrization give a circle in u-space, and the second two coordinates give a circle in v-space. The 4-D torus is thus the Cartesian Product of two circles. + - A [[Stereographic Projection| stereographic projection]] is used to map this 4-D object into 3-D, using a projection point of $(0,0,0,\sqrt{2})$ for the first object in this page's main image. This projection is centered above the four-dimensional object, projecting the symmetric torus into three-dimensional space. For the second object, the projection point is shifted to be closer to one part of the four-dimensional object than the other, creating an uneven object in 3-D. This projection's unevenness is similar to the shadow of a symmetric object becoming asymmetric because of the light source's positioning. + |ImageDesc= A [[torus]] is commonly known as the surface of a doughnut shape. It can be described using [[Parametric Equations|parametric equations]]. While it is a two dimensional surface , it lives in three dimensional space. + + A four-dimensional torus is an analogous object that lives in four dimensional space. The main image contains two images which ways of visualizing a four dimensional torus in three dimensions. + + The four-dimensional torus is defined [[Parametric Equations|parametrically]] by $(x_1,\,x_2,\,x_3,\,x_4)=(cos(u),\,sin(u),\,cos(v),\,sin(v))$. The first two coordinates of the parametrization give a circle in u-space, and the second two coordinates give a circle in v-space. The torus is thus the [[Cartesian Product]] of two circles. + + A [[Stereographic Projection| stereographic projection]] is used to map this object, which lives in four-dimensional space, into three-dimensional space, using a projection point of $(0,0,0,\sqrt{2})$ for the first object in this page's main image. This projection is centered above the object, projecting the symmetric torus into three-dimensional space. For the second object, the projection point is shifted to be closer to one part of the four-dimensional object than the other, creating an uneven object in three dimensions. This projection's unevenness is similar to the shadow of a symmetric object becoming asymmetric because of the light source's positioning. |AuthorName=Thomas F. Banchoff |AuthorName=Thomas F. Banchoff - |AuthorDesc=Thomas F. Banchoff is a geometer, and a professor at Brown University since 1967. + |AuthorDesc=Thomas F. Banchoff is a geometer, and a professor at Brown University since 1967. |SiteName=The Mathematics of In- and Outside the Torus |SiteName=The Mathematics of In- and Outside the Torus |SiteURL=http://www.math.brown.edu/~banchoff/art/PAC-9603/tour/torus/torus-math.html |SiteURL=http://www.math.brown.edu/~banchoff/art/PAC-9603/tour/torus/torus-math.html |Field=Algebra |Field=Algebra + |References=http://www.math.brown.edu/~banchoff/art/PAC-9603/tour/torus/torus-math.html |InProgress=No |InProgress=No }} }}

## Current revision

4-Dimensional Torus
Field: Algebra
Image Created By: Thomas F. Banchoff
Website: The Mathematics of In- and Outside the Torus

4-Dimensional Torus

A torus in four dimensions projected into three-dimensional space.

# Basic Description

It is impossible to visualize an object in four-dimensions, since we have only ever lived in three-dimensional space. However, there are ways to capture features of the four-dimensional object in three-dimensional space.

A useful analogy is a world map. We can capture the essence of the three-dimensional globe on a two-dimensional map, but only by using a projection, which translates a three-dimensional object onto a two-dimensional surface at the expense of distorting the object in some way.

A similar process is carried out to create this page's main image. An object in four-dimensional space, described further below, is projected into three-dimensions using two different projections.

# A More Mathematical Explanation

A torus is commonly known as the surface of a doughnut shape. It can be described using [[Paramet [...]

A torus is commonly known as the surface of a doughnut shape. It can be described using parametric equations. While it is a two dimensional surface , it lives in three dimensional space.

A four-dimensional torus is an analogous object that lives in four dimensional space. The main image contains two images which ways of visualizing a four dimensional torus in three dimensions.

The four-dimensional torus is defined parametrically by $(x_1,\,x_2,\,x_3,\,x_4)=(cos(u),\,sin(u),\,cos(v),\,sin(v))$. The first two coordinates of the parametrization give a circle in u-space, and the second two coordinates give a circle in v-space. The torus is thus the Cartesian Product of two circles.

A stereographic projection is used to map this object, which lives in four-dimensional space, into three-dimensional space, using a projection point of $(0,0,0,\sqrt{2})$ for the first object in this page's main image. This projection is centered above the object, projecting the symmetric torus into three-dimensional space. For the second object, the projection point is shifted to be closer to one part of the four-dimensional object than the other, creating an uneven object in three dimensions. This projection's unevenness is similar to the shadow of a symmetric object becoming asymmetric because of the light source's positioning.

# Teaching Materials

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# About the Creator of this Image

Thomas F. Banchoff is a geometer, and a professor at Brown University since 1967.

# References

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