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 Post subject: Chaos - definition.
PostPosted: Thu, 17 Nov 2011 22:14:09 UTC 
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While reading the book I came across the concept of chaos. Is there any mathematical definition of chaos?


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 Post subject: Re: Chaos - definition.
PostPosted: Thu, 17 Nov 2011 22:26:35 UTC 
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http://en.wikipedia.org/wiki/Chaos_theory

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 Post subject: Re: Chaos - definition.
PostPosted: Thu, 17 Nov 2011 23:29:56 UTC 
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I read it, but I still do not know how to strictly define chaos. I would like to use the definition of chaos in the introductory paper on chaos theory or the theory of dynamical systems, so I need a definition with objectives/equations, etc. Could you give me any example of chaos and say why it is chaos?


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 Post subject: Re: Chaos - definition.
PostPosted: Thu, 17 Nov 2011 23:30:54 UTC 
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KamilJ wrote:
I read it, but I still do not know how to strictly define chaos. I would like to use the definition of chaos in the introductory paper on chaos theory or the theory of dynamical systems, so I need a definition with objectives/equations, etc. Could you give me any example of chaos and say why it is chaos?


Chaos is a subject, not a mathematical construct, so it's definition is fundamentally descriptive, and not mathematical.

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 Post subject: Re: Chaos - definition.
PostPosted: Wed, 30 Nov 2011 19:45:48 UTC 
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Thank you for help.

Could you tell me one more thing - where can I find a well described Smale horseshoe?


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 Post subject: Re: Chaos - definition.
PostPosted: Thu, 1 Dec 2011 00:27:21 UTC 
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http://www.scholarpedia.org/article/Smale_horseshoe

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 Post subject: Re: Chaos - definition.
PostPosted: Sat, 3 Dec 2011 18:58:29 UTC 
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Chaos is a subject, not a mathematical construct, so it's definition is fundamentally descriptive, and not mathematical.

I agree with shadow.


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 Post subject: Re: Chaos - definition.
PostPosted: Sat, 3 Dec 2011 19:19:50 UTC 
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Is it the same with the bifurcation?


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 Post subject: Re: Chaos - definition.
PostPosted: Sun, 4 Dec 2011 08:49:11 UTC 
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KamilJ wrote:
Is it the same with the bifurcation?


No. Bifurcation is very precisely defined, e.g. for continuous-time dynamical systems arising from ODE, bifurcation of an autonomous system of ODE \dot{x}=f(x,c) occurs at c=c_0 when arbitrarily close to this parameter value, there are other parameter values c that the dynamical system isn't (topological/differential/... depending on the category) conjugate to the original system.

The usual hiding behind a descriptive picture is just that you don't really want to go on a detour into defining these terms (usually defined in the second course on differential equations/dynamical systems/whatever they call it, i.e. the next course after introduction of things like Poincar\'{e}-Bendixon theorem).

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\begin{aligned}
Spin(1)&=O(1)=\mathbb{Z}/2&\quad&\text{and}\\
Spin(2)&=U(1)=SO(2)&&\text{are obvious}\\
Spin(3)&=Sp(1)=SU(2)&&\text{by }q\mapsto(\mathop{\mathrm{Im}}\mathbb{H}\ni p\mapsto qp\bar{q})\\
Spin(4)&=Sp(1)\times Sp(1)&&\text{by }(q_1,q_2)\mapsto(\mathbb{H}\ni p\mapsto q_1p\bar{q_2})\\
Spin(5)&=Sp(2)&&\text{by }\mathbb{HP}^1\cong S^4_{round}\hookrightarrow\mathbb{R}^5\\
Spin(6)&=SU(4)&&\text{by the irrep }\Lambda_+\mathbb{C}^4
\end{aligned}


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 Post subject: Re: Chaos - definition.
PostPosted: Sun, 4 Dec 2011 18:43:00 UTC 
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So what is the definition for chaotic systems?

I am after first course of differential equations, so I don't know how should I understand that. I'm reading some book about chaos theory (introduction) and I'm trying to get familiar with idea of bifurcation and bifurcation diagrams.

Maybe I should ask: how should I start with chaos theory? I've read that dynamical system is chaotic, if it is transitive and the set of periodic points is dense. I have also read about logistic map, attractors, repellers and some older student told me, that I should next know what is bifurcation. I can't help feeling, that I got lost in it.


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