Explaining Catastrophe Theory for an Infinite 2D Body

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Discussion Overview

The discussion revolves around the application of Catastrophe Theory to an infinite 2D body bounded by a parabola, focusing on the dynamics of the center of mass and the conditions under which the body undergoes a sharp swing. Participants explore the implications of this phenomenon and seek to identify a specific line, referred to as line C, that influences the behavior of the body.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants describe the initial stable position of the body and how the center of mass movement leads to changes in its position.
  • One participant suggests that the dynamics can be related to the abrupt changes in the zeros of a polynomial as the plot is shifted, indicating a potential connection to Catastrophe Theory.
  • Another participant introduces the concept of cusp catastrophe and discusses the bifurcation points, explaining how these relate to stable and unstable states of the system.
  • A later reply elaborates on the analogy of a vase on a table to illustrate the concept of bifurcation points and the transition between stable states.
  • Some participants express uncertainty about where to start with the project and seek additional resources to better understand Catastrophe Theory.

Areas of Agreement / Disagreement

Participants generally agree on the relevance of Catastrophe Theory to the problem, but multiple competing views on the specifics of the dynamics and the identification of line C remain unresolved.

Contextual Notes

There are limitations in the discussion regarding the clarity of the problem due to inaccessible external resources, as well as the need for further exploration of the mathematical underpinnings of the concepts discussed.

Who May Find This Useful

This discussion may be useful for students and researchers interested in Catastrophe Theory, particularly in understanding its application to physical systems and the dynamics of stability and instability.

boatzanshoe
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Consider an infinite 2D body, bounded by a parabola. It is made of an non-uniform material, so it's center of mass is finite. Initlaly, the body lies on a horizontal line in a stable position, so that the line that connects the center of mass with the bottom point is normal to the boundary. The center of mass starts moving, and the body changes its position. Sometimes, when the center of mass crosses certain line C (shown in red at the picture), the body makes a sharp swing. Explain this phenomenon, and find the line C.

http://www.math.uiuc.edu/~roitman/m...catastrophe.gif


help me out guys, I am really really

...
 
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Please don't duplicate post!
 
More importantly, please explain your reasoning first, so we can pinpoint where you got stuck!
 
boatzanshoe said:
Consider an infinite 2D body, bounded by a parabola. It is made of an non-uniform material, so it's center of mass is finite. Initlaly, the body lies on a horizontal line in a stable position, so that the line that connects the center of mass with the bottom point is normal to the boundary. The center of mass starts moving, and the body changes its position. Sometimes, when the center of mass crosses certain line C (shown in red at the picture), the body makes a sharp swing. Explain this phenomenon, and find the line C.

http://www.math.uiuc.edu/~roitman/m...catastrophe.gif


help me out guys, I am really really

...

Your website is not connecting so I can't see the problem but what I've often found in Catastrophe Theory is the dynamics can be reduced to how the zeros of a polynomial abruptly change as the plot is "shifted" up or downward. I wouldn't be surprised, even without looking at the problem, if it can be reduced to this phenomenon.
 
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saltydog said:
Your website is not connecting so I can't see the problem but what I've often found in Catastrophe Theory is the dynamics can be reduced to how the zeros of a polynomial abruptly change as the plot is "shifted" up or downward. I wouldn't be surprised, even without looking at the problem, if it can be reduced to this phenomenon.


https://netfiles.uiuc.edu/phsu2/shared/catastrophe.gif?uniq=wdarem


im sorry about the double post.

to tell you the truth, i have no idea where to start. my teacher kind of just threw this project at me.

are there some websites that might help me understand the catastrophe theory better? I've look at a lot of them, but i can't seem to understand much of it.

thank you for your help!
 
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boatzanshoe said:
https://netfiles.uiuc.edu/phsu2/shared/catastrophe.gif?uniq=wdarem


im sorry about the double post.

to tell you the truth, i have no idea where to start. my teacher kind of just threw this project at me.

are there some websites that might help me understand the catastrophe theory better? I've look at a lot of them, but i can't seem to understand much of it.

thank you for your help!

That's got cusp catastrophe written all over it. The red plot (cusp) is the bifurcation set but that's not helpful is it? I tell you what, the best way to study the cusp catastrophe is to study the following cubic differential equation:

[tex]\frac{dy}{dx}=c+ky-y^3[/tex]

In that case, we study the abrupt changes that the roots of a cubic polynomial undergo as the plot is shifted up or down, you know, from 1 to 1 double+another, to three and back again.

Also, check out Saunders, "An Introduction to Catastrophe Theory". Rene' Thom is the father of such. Please, allow me to quote a profound statement he made:

"all creation or destruction of forms or morphogenesis, can be described by the disappearance of the attractors representing the initial forms, and the replacement by capture by the attractors representing the final forms".

The changes are catastrophic . . . you know, the straw that breaks the camel's back. Lots of things in nature are like that right?
 
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Here's the cusp catastrophe. Think about being on the upper fold of the surface and moving to the left. Eventually you fall off and end up on the bottom fold. The points on top where you fall off are the bifurcation points. A 2-D plot of those points is the bufurcation points (red diagram in your figure).

The top surface represents "stable states" like a vase on the top of a table that you move about on the table. Nothing much happens. However, if you move the vase to the very edge of the table. It's now on it's bifurcation curve. Moving it ever so slightly and it will "traject" abruptly and qualitatively change states from being a stable vase on a table to a broken one on the floor.

In the language of Rene' Thom, the table surface is a basin of attraction for the stable state of the vase on the table. Pushing it past it's bifurcation point, and it moves into the basin of attraction of the floor attractor and undergoes "morphogenesis" in passing through the bifurcation point to the new stable state (analogous to the bottom fold of the cusp).

Yea, I know what you're thinking, "nevermind Salty, anyone else up there?".
 

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