Henon Attractor
From Math Images
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Image=HenonMain.jpg  Image=HenonMain.jpg  
ImageIntro=This image is a Henon Attractor (named after astronomer and mathematician Michel Henon), which is a fractal in the division of the chaotic strange attractor.  ImageIntro=This image is a Henon Attractor (named after astronomer and mathematician Michel Henon), which is a fractal in the division of the chaotic strange attractor.  
  ImageDescElem=  +  ImageDescElem=The Henon Attractor is a special kind of fractal that belongs in a group called [[Strange Attractors]], and can be modeled by two general equations. The Henon Attractor is created by applying this system of equations to a starting value over and over again and graphing each result. 
  The Henon Attractor is a special kind of fractal that belongs in a group called [[Strange Attractors]], and can be modeled by two general equations. The Henon Attractor is created by applying this system of equations to a starting value over and over again and graphing each result.  +  
===Making the Henon Attractor===  ===Making the Henon Attractor===  
<div style="width:265px; height:225px; float:left;">{{#eqt: HenonAnimation.avi250left}}</div>  <div style="width:265px; height:225px; float:left;">{{#eqt: HenonAnimation.avi250left}}</div>  
+  
+  
+  Say we took a single starting point (x,y) and plotted it on a graph. Then, we applied the <balloon title="One equation for the xvalue and one equation for the yvalue.">two</balloon> Henon Attractor equations to the initial point and emerged with a new point that we graphed. Next, we took this new point and again applied the two equations to it and graphed the next new point. If we continued to apply the two equations to each new point in a process called '''iteration''' and plotted every outcome from this iteration, we would create a Henon Attractor. Click here to learn more about [[Iterated Functionsiterated functions]].  
+  
+  
+  Furthermore, if we plotted each outcome one at a time, we would observe that the points jump from one random location to another within the image. If you take a look at the animation, you can see the irregularity of the plotted points. Eventually, the individual points become so numerous that they appear to form lines and an image emerges.  
+  
+  
+  
+  
+  ===Magnification of the Henon Attractor===  
+  <gallery caption="" widths="220px" heights="150px" perrow="4">  
+  Image:HenonMag1.png  
+  ImageDesc===Fractal Properties==  
+  {{Switchlink1=Showlink2=Hide  
+  1=[[Image:HenonZoomAnimation.gif150px]]  
+  2=[[Image:HenonZoomAnimation.gifrightthumbZooming in on the Henon Attractor]]  
+  
+  
+  The Henon Attractor is often described as being similar to the [[Cantor Set]]. Let us zoom into the Henon Attractor near the doubledtip of the fractal (as seen in the animation). We can see that as we continue to magnify the lines that form the structure of the Henon Attractor, these lines become layers of increasingly deteriorating lines that appear to resemble the Canter Set.  
+  
+  
+  The [[Fractal Dimension]] of the Henon Attractor is not calculable using a single <balloon title = "load:equation"> equation</balloon><span id="equation" style="display:none"><math>D = \frac{log(n)}{log(e)}</math></span>, but it is estimated to be about 1.261.  
+  }}  
+  
+  
+  ==Chaotic System==  
+  {{hide1=  
+  [[Image:Henon2.jpgrightthumbOriginal Henon Attractor, a = 1.4, b = 0.3]]  
+  The Henon system can be described as [[Chaoschaotic]] and random. However, the system does have structure in that its points settle very close to an underlying pattern called a <balloon title="In a chaotic system like this fractal, over time plotted points are evolving towards (or being 'attracted' to) a region that is called the chaotic attractor.">chaotic attractor</balloon>. The basic Henon Attractor can be described by the equations, where <math>x_n</math> is the xvalue at the nth iteration.  
+  
+  
+  ::<math>x_{n+1} = y_n + 1  ax^2_n</math>  
+  
+  
+  ::<math>y_{n+1} = bx_n\,</math>  
+  
+  
+  Astronomer Michel Henon created the original Henon Attractor using the values ''a'' = 1.4 and ''b'' = 0.3 and starting point (1,1). These are also the values used by the artist to create the featured image at the top of the page. However, by changing the values of ''a'' and ''b'', we can obtain Henon Attractors that look slightly different.  
+  }}  
+  
+  
+  ==Changing "a" and "b"==  
+  {{Switchlink1=Showlink2=Hide1=[[Image:Henon.jpg200px]]2=  
+  Although the original Henon Attractor uses ''a'' = 1.4 and ''b'' = 0.3, we can alter those values slightly to produce variouslooking Henon Attractors. However, the values of ''a'' and ''b'' are limited to a small range of values, outside of which the fractal ceases to resemble the Henon Attractor.  
+  
+  
+  Here are some more examples of Henon Attractors with different ''a'' and ''b'' values.  
+  
+  <gallery widths="250px" heights="250px" perrow="3" align ="center">  
+  Image:Henon.jpga = 1; b = 0.542  
+  Image:Henon_a1.2_b0.3.pnga = 1.2; b = 0.3  
+  Image:Henon_a1.3_b0.3.pnga = 1.3; b = 0.3 (points need to be enlarged)  
+  Image:Henon_a1.4_b0.3.pnga = 1.4; b = 0.3, original Henon Attractor  
+  Image:Henon_a1.5_b0.2.pnga = 1.5; b = 0.2  
+  Image:Henon_a1.4_b0.1.pnga = 1.4; b = 0.1  
+  </gallery>  
+  
+  
+  }}  
+  
+  
+  ==Fixed Points==  
+  {{Switchlink1=Showlink2=Hide  
+  1=[[Image:HenonFixedPoints1.png180px]]  
+  2=[[Image:HenonFixedPoints1.pngthumb325pxrightOriginal Henon Attractor with fixed points 1 and 2]]  
+  Looking at the <balloon title="load:eqns">system of equations</balloon> <span id="eqns" style="display:none"><math>x_{n+1} = y_n + 1  ax^2_n</math> and <math>y_{n+1} = bx_n\,</math></span> that describe the fractal, the Henon Attractor uses only two variables (x and y) that are evaluated into themselves. This results in two equilibrium or fixed points for the attractor. Fixed points are such that if the two Henon Attractor equations are applied to the fixed points, the resulting points would be the same fixed points. In algebraic terms:  
+  
+  
+  :<math>x_{n+1} = x_n\,</math> and <math>y_{n+1} = y_n\,</math>  
+  
+  
+  :where <math>x_n</math> is the xvalue at the nth iteration and <math>x_{n+1}</math> is the xvalue at the next iteration.  
+  
+  
+  Therefore, if the system ever plotted onto the fixed points, the fractal would become stagnant. By solving the Henon Attractor's system of equations with a = 1.4 and b = 0.3, we can find that the fixed points for the original Henon Attractor are (0.6314 , 0.1894) and (1.1314 , 0.3394).  
+  
+  {{HideThis1=Solving the System of Equations2=  
+  To solve the system of equations:  
+  
+  :<math>x_{n+1} = y_n + 1  ax^2_n</math>  
+  
+  :<math>y_{n+1} = bx_n\,</math>  
+  
+  
+  Since <math>x_{n+1} = x_n\,</math> and <math>y_{n+1} = y_n\,</math>, we can simplify the equations and refer to the variables as just <math>x</math> and <math>y</math>, respectively  
+  
+  :<math>x = y + 1  ax^2</math>  
+  
+  :<math>y = bx\,</math>  
+  
+  
+  By substituting the value of <math>y</math> defined by the second equation into the <math>y</math> in the first equation, we get  
+  
+  :<math>x = bx + 1  ax^2</math>  
+  
+  
+  Using the <balloon title = "load:quadeqn"> quadratic equation </balloon>  
+  <span id="quadeqn" style="display:none"> <math>x_{1,2} = \frac{b \pm \sqrt{b^2  4ac} }{2a}</math> </span>  
+  
+  :<math>x = \frac{(b1) \pm \sqrt{(b1)^2  4(a)(1)}}{2(a)}</math>  
+  
+  
+  :<math>x = \frac{(b1) \pm \sqrt{(b1)^2 + 4a}}{2a}</math>  
+  
+  
+  Using a = 1.4, b = 0.3:  
+  
+  :<math>x = 0.6314, 1.1314 \, </math>  
+  
+  
+  Using y = bx:  
+  
+  :<math>y = 0.1894, 0.3394 \, </math>  
+  }}  
+  
+  
+  There are two types of fixed points, '''stable''' and '''unstable'''. The first fixed point (0.6314, 0.1894), labeled "1" on the image, is located within the attractor itself and is stable. This means that if a point is plotted close to the fixed point, the next iterated points will remain close to the fixed point. The second fixed point (1.1314 , 0.3394), labeled "2", is considered unstable, and it is located outside of the bounds of the attractor. An unstable fixed point is such that if the system gets close to the fixed point, the next iterated points rapidly move away from the fixed point.  
+  }}  
+  other=Algebra  
+  AuthorName=Piecewise Affine Dynamics  
+  AuthorDesc=Piecewise Affine Dynamics is a wiki site that was created by a group of French mathematicians that is dedicated to providing information about "dynamic systems defined by piecewise affine transformations".  
+  SiteName=Lozi Maps  
+  SiteURL=http://padyn.wikidot.com/lozimaps  
+  Field=Dynamic Systems  
+  Field2=Fractals  
+  References=:*Glenn Elert, [http://hypertextbook.com/chaos/21.shtml The Chaos Hypertextbook]  
+  HeinzOtto Peitgen, Hartmut Jürgens, Dietmar Saupe, '''Chaos and fractals'''  
+  
+  :*Bill Casselman, [http://www.ams.org/featurecolumn/archive/henon.html Simple ChaosThe Hénon Map]  
+  
+  :*www.ibiblio.org [http://www.ibiblio.org/enotes/Chaos/strange.htm Henon Strange Attractors]  
+  
+  :*Michele Henon, [http://www.exploratorium.edu/turbulent/CompLexicon/henon.html Michele Henon]  
+  ToDo=:*A better, less vague description of how sections of the Henon Attractor resembles the Cantor Set  
+  :*Also, the description of the Henon Attractor can be expanded to include a discussion about the fractal's "basin of attraction". For more information, click [http://www.ams.org/featurecolumn/archive/henon.html here].  
+  InProgress=No  
+  }}  
+  </div>  
Revision as of 12:13, 16 July 2009
Henon Attractor 

Henon Attractor
 This image is a Henon Attractor (named after astronomer and mathematician Michel Henon), which is a fractal in the division of the chaotic strange attractor.
Contents 
Basic Description
The Henon Attractor is a special kind of fractal that belongs in a group called Strange Attractors, and can be modeled by two general equations. The Henon Attractor is created by applying this system of equations to a starting value over and over again and graphing each result.
Making the Henon Attractor
Say we took a single starting point (x,y) and plotted it on a graph. Then, we applied the two Henon Attractor equations to the initial point and emerged with a new point that we graphed. Next, we took this new point and again applied the two equations to it and graphed the next new point. If we continued to apply the two equations to each new point in a process called iteration and plotted every outcome from this iteration, we would create a Henon Attractor. Click here to learn more about iterated functions.
Furthermore, if we plotted each outcome one at a time, we would observe that the points jump from one random location to another within the image. If you take a look at the animation, you can see the irregularity of the plotted points. Eventually, the individual points become so numerous that they appear to form lines and an image emerges.
Magnification of the Henon Attractor
==Chaotic System==

==Changing "a" and "b"==

Here are some more examples of Henon Attractors with different ''a'' and ''b'' values.


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Fixed Points
Looking at the system of equations that describe the fractal, the Henon Attractor uses only two variables (x and y) that are evaluated into themselves. This results in two equilibrium or fixed points for the attractor. Fixed points are such that if the two Henon Attractor equations are applied to the fixed points, the resulting points would be the same fixed points. In algebraic terms:
 and
 where is the xvalue at the nth iteration and is the xvalue at the next iteration.
Therefore, if the system ever plotted onto the fixed points, the fractal would become stagnant. By solving the Henon Attractor's system of equations with a = 1.4 and b = 0.3, we can find that the fixed points for the original Henon Attractor are (0.6314 , 0.1894) and (1.1314 , 0.3394).
To solve the system of equations:
Since and , we can simplify the equations and refer to the variables as just and , respectively
By substituting the value of defined by the second equation into the in the first equation, we get
Using the quadratic equation
Using a = 1.4, b = 0.3:
Using y = bx:
other=Algebra
AuthorName=Piecewise Affine Dynamics
AuthorDesc=Piecewise Affine Dynamics is a wiki site that was created by a group of French mathematicians that is dedicated to providing information about "dynamic systems defined by piecewise affine transformations".
SiteName=Lozi Maps
SiteURL=http://padyn.wikidot.com/lozimaps
Field=Dynamic Systems
Field2=Fractals
References=:*Glenn Elert, The Chaos Hypertextbook
HeinzOtto Peitgen, Hartmut Jürgens, Dietmar Saupe, Chaos and fractals
 Bill Casselman, Simple ChaosThe Hénon Map
 www.ibiblio.org Henon Strange Attractors
 Michele Henon, Michele Henon
ToDo=:*A better, less vague description of how sections of the Henon Attractor resembles the Cantor Set
 Also, the description of the Henon Attractor can be expanded to include a discussion about the fractal's "basin of attraction". For more information, click here.
InProgress=No }} </div>
Say we took a single starting point (x,y) and plotted it on a graph. Then, we applied the two Henon Attractor equations to the initial point and emerged with a new point that we graphed. Next, we took this new point and again applied the two equations to it and graphed the next new point. If we continued to apply the two equations to each new point in a process called iteration and plotted every outcome from this iteration, we would create a Henon Attractor. Click here to learn more about iterated functions.
Furthermore, if we plotted each outcome one at a time, we would observe that the points jump from one random location to another within the image. If you take a look at the animation, you can see the irregularity of the plotted points. Eventually, the individual points become so numerous that they appear to form lines and an image emerges.
Magnification of the Henon Attractor
If you magnify this image, you would find that the lines (really many, many points) that appear to be single lines on the larger image are actually sets or bundles of lines, that, if magnified closer, are bundles of lines and so on. This property is called selfsimilarity, which means that even as you look closer and closer into the image, it continues to look the same. In other words, the larger view of the image is similar to a magnified part of the image.
History of the Henon Attractor
Michel Henon was a French mathematician and astronomer who developed the Henon Attractor in the 1970s. At that time, Henon was interested in dynamical systems and especially the complicated orbits of celestial objects. The Henon Attractor emerged from Henon's attempt to model the chaotic orbits of celestial objects (like stars) in the mist of a gravitational force.
PreK=No
Elementary=Yes
MiddleSchool=Yes
HighSchool=Yes
ImageDesc=
Fractal Properties
The Henon Attractor is often described as being similar to the Cantor Set. Let us zoom into the Henon Attractor near the doubledtip of the fractal (as seen in the animation). We can see that as we continue to magnify the lines that form the structure of the Henon Attractor, these lines become layers of increasingly deteriorating lines that appear to resemble the Canter Set.
Chaotic System
Changing "a" and "b"
Here are some more examples of Henon Attractors with different a and b values.
Fixed Points
Looking at the system of equations that describe the fractal, the Henon Attractor uses only two variables (x and y) that are evaluated into themselves. This results in two equilibrium or fixed points for the attractor. Fixed points are such that if the two Henon Attractor equations are applied to the fixed points, the resulting points would be the same fixed points. In algebraic terms:
 and
 where is the xvalue at the nth iteration and is the xvalue at the next iteration.
Therefore, if the system ever plotted onto the fixed points, the fractal would become stagnant. By solving the Henon Attractor's system of equations with a = 1.4 and b = 0.3, we can find that the fixed points for the original Henon Attractor are (0.6314 , 0.1894) and (1.1314 , 0.3394).
To solve the system of equations:
Since and , we can simplify the equations and refer to the variables as just and , respectively
By substituting the value of defined by the second equation into the in the first equation, we get
Using the quadratic equation
Using a = 1.4, b = 0.3:
Using y = bx:
other=Algebra
AuthorName=Piecewise Affine Dynamics
AuthorDesc=Piecewise Affine Dynamics is a wiki site that was created by a group of French mathematicians that is dedicated to providing information about "dynamic systems defined by piecewise affine transformations".
SiteName=Lozi Maps
SiteURL=http://padyn.wikidot.com/lozimaps
Field=Dynamic Systems
Field2=Fractals
FieldLinks =
References=
Glenn Elert, The Chaos Hypertextbook
HeinzOtto Peitgen, Hartmut Jürgens, Dietmar Saupe, Chaos and fractals
Bill Casselman, Simple ChaosThe Hénon Map
www.ibiblio.org Henon Strange Attractors
Michele Henon, Michele Henon ToDo= A better, less vague description of how sections of the Henon Attractor resembles the Cantor Set Also, the description of the Henon Attractor can be expanded to include a discussion about the fractal's "basin of attraction". For more information, click here. HideMME=No }}