In dynamical systems, the motion of a particle in some geometric space, governed by some time dependent rules, is studied. The process can be discrete (where the particle jumps from point to point) or continuous (where the particle follows a trajectory). Dynamical systems is used in mathematical ...

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Question related to the ballistic motion

A point mass will move in the gravitational field of the Earth according to the equation $$\ddot R =-\frac{GM_eR}{|R|^3},$$ where $R$ is the position vector of the point mass measured from the ...
1
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1answer
16 views

Conditions for Deriving $R_0$ for SIR Model Using Survival Function Method

I'm taking a look at the SIR model given by the system of differential equations \begin{align} \frac{dS}{dt} & = - \beta S I \\ \frac{dI}{dt} & = \beta S I - \gamma I \\ \frac{dR}{dt}& ...
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0answers
20 views

Eigenvectors question

$x'=x-2y$ $y'=4x-x^3$ Consider equilibrium point $(2,1)$: Let $X=x-2$ and $Y=y-1$. Subbing this into the main and eliminating all the nonlinear terms gives: $x'=X-2Y$ $y'=-8X$ Giving the ...
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1answer
25 views

Sketching phase portrait

$\dot{x}=-2x-2y$ $\dot{y}=-x-3y$ Equilibrium point is $(0,0)$. Eigenvalues are $\lambda_+=-1$ and $\lambda_-=-4$ which have corresponding eigenvectors $2\choose -1$ and $1 \choose 1$ respectively. ...
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21 views

Stubborn dynamical system state

It is rather common to use matrices to represent the relationship of the states of dynamical systems. It is very natural to use matrices because of their ease in analysis. Stability, convergence ...
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16 views

Characterizing equicontinuity via ultrafilters

We have a compact metric space $(X,d)$ and a homeomorphism $T:X\to X$. For any ultrafilter $p\in\beta\mathbb{Z}$ we can define the map $T^p:X\to X$ given by $T^p(x):=\lim_{n\to p}T^n x$ (which can ...
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0answers
16 views

Bifurcations in the Duffing oscillator

I'm trying to describe all the bifurcations in the two parameter Duffing oscillator: $$\ddot{x} + ax + bx^3 = 0$$ In phase space with $y = \dot{x}$ I've found the origin to be a centre for $a>0$ ...
2
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1answer
36 views

How to proof that bracket of two vector field can be computed by second derivation

Can some one give a hint how can I proof that where $\phi$ indicated the flow of vector fields.
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1answer
35 views

Show system of ODEs has a periodic solution by finding smallest annular trapping region

Find the smallest annular trapping region of the following: $r'=r(1-2r^2+sin(2\theta)r^2)$ $\theta ' = -1$ I really do not understand how to do this. I have been trying to figure it out from things ...
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0answers
15 views

A question regarding space-state representation

First of all I am not sure if this is the right place to ask this. Lets say we have a system in a form of a harmonic oscillator desribed by a second order DE. There will be 2 state variables - x ...
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0answers
18 views

How to diagonalise this pentadiagonal pseudo-Toeplitz matrix?

How can one diagonalise this N-by-N pentadiagonal matrix (where $r$ is some real constant)? $$ \tiny \begin{pmatrix} r^2 +r & -2r -1 & 1 & & & & & & ...
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25 views

Continuity with respect to initial conditions [closed]

Let $\varphi(t,x_0)$ be the solution of the initial value problem $x'= Ax$. Use the Fundamental Theorem to show that for each fixed $t\in\mathbb{R}$ $\lim_{y\rightarrow x_0} \varphi(t,y) = ...
0
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0answers
23 views

Topological entropy of circle homeomorphism is zero. True or false?

may I know if it is true that $\ f: S^1 \to S^1$ a homeomorphism, then $h_{top}(f) = 0$, where $h_{top}$ stands for topological entropy. I believe this statement is true, but I cannot prove it.
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67 views

We all know about compositions of functions, but what about decomposition. Is there a way with math, not just heuristics?

The composition operator is a well know and quite often used method in integration and differentiation, think u-substitution. However, given a composition like $$f(f(f(...f(x)...)))$$ Where there are ...
1
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0answers
17 views

T invariant probability measure on a compact space $X$

Let $T:X\to X$ be a continuous map defined on the compact space $X$. I read that if $X$ is a metric space then the set of T-invariant probability measure is not empty. I want to know if this result ...
0
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0answers
26 views

the $C^2$ structural stability of maps on $S^1$

Let $f, g:S^1\rightarrow S^1$ be two $C^2$ maps, $q\in S^1$ be such that $\inf_{n\geq 0}(f^n(q), C_f)>0$ where $C_f$ is the critical points of $f$, i.e., $C_f=\{x\in S^1:f'(x)=0\}.$ Assume that all ...
4
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1answer
34 views

Beta transformation is Ergodic.

Let $\beta \in \mathbb{R}$ with $\beta >1$. Define $T_{\beta}:[0,1)\to [0,1)$ by: $$T_{\beta}(x)=\beta x-[\beta x]=\{\beta x\} $$. Consider: $$ ...
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0answers
25 views

Stability of Linear Systems. BIBO Stable, but Lyapunov Unstable System [closed]

I need help in this question. Let the input u ≡ 0. Determine the states x1 and x2 and the output y. For what set of initial conditions [x10 x20]T will the output be zero? This is the answer. But I ...
2
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1answer
19 views

Expanding maps of the circle and their coding

A continuous smooth ($C^{10}$-smooth, for example) map $f:S^1\to S^1$ of the circle is called expanding if $\inf_{x\in S^1} f'(x) > 1 $. Here $S^1 = [0,1]/\sim$, the segment with identified ...
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0answers
23 views

Components of a matrix ($\mathbb{R}$, $\mathbb{C}$, $X$, and others?) [closed]

Define: A state of a system at time $t$ is represented by the vector $A_t = \begin{pmatrix} A_1 \\ A_2 \end{pmatrix}$. The transformation of the state is given by $B$. So far the most common (from ...
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0answers
15 views

Question about history of Entropy

I have started to study Ergodic theory and entropy by some books and lecture notes more than three months but unfortunately I'm not familiar with history of Entropy (I know some thing about name of ...
1
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1answer
50 views

A dynamical system of differential equations - periodic solutions?

I am solving a physical problem with a known periodic solution. When I simulate the behaviour of the system numerically, with full blown differential equations, I get stable, but rather complicated ...
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0answers
44 views

Is there an elegant proof of this elementary bifurcation theory result?

Let's suppose I have a $C^1$ function $f:\mathbb{R}\times\mathbb{R}\rightarrow\mathbb{R}$, $(x,\lambda)\mapsto f(x,\lambda)$. Suppose there is a unique solution of the equation $f(x,\lambda_1)=0$, ...
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2answers
42 views

Can there be an interval where $F(x)=4 x^2-\frac{1}{2}$ is chaotic?

The function $$F(x)=4 x^2-\frac{1}{2}$$ has two repelling fixed points. Now, I wonder, can there be an interval $I$ where it is chaotic? I think not, because of the repulsiveness of the fixed points. ...
18
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427 views

This one weird thing that bugs me about summation and the like

Most of us know $$\sum_{n=a}^b c_n=c_a+c_{a+1}...+c_{b-1}+c_b$$ Some of us know $$\prod_{n=a}^b c_n=c_a \cdot c_{a+1}...c_{b-1} \cdot c_{b}$$ A few of us know ...
1
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1answer
47 views

Prove that if $x<0$ then $F_\mu^n(x)\rightarrow -\infty$ as $n\rightarrow \infty$, where $F_\mu=\mu x(1-x)$.

Logistic map is given as $$x_{n+1}=\mu x_n(1-x_n)$$ Let $F_\mu=\mu x(1-x)$. Therefore, for $\mu>1$, prove that if $x<0$ then $F_\mu^n(x)\rightarrow -\infty$ as $n\rightarrow \infty$.
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17 views

Recursion and splitting into even and odd parts

Given the relations $v_{2i}=v_i$ and $v_{2i+1}=-v_{i}$ and $\eta(m)=\lim_{n\to\infty}\frac{1}{N}\sum_{i=0}^{N-1}v_{i}v_{i+m}$. I want to show $\eta(m)=$\eta(2m)$. $\textnormal{Part of the hint is to ...
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1answer
17 views

Introducing noise and time lag between two coupled Rössler systems

I have two Rössler systems mutually coupled by the second component. I want to introduce some small noise and a slight time lag of the coupling between the systems. I'm not sure 1. what the best ...
1
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0answers
23 views

Qualitative properties of eigenvalues that can be inferred from matrix structure?

I am doing a linear stability analysis of a 6-dimensional system, what I want to know is if the system is stable at numerically solved steady states by looking at the eigenvalues of the jacobian ...
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0answers
12 views

Is this correct, the Jacobian of the function $G(y_n)=(x_{n+1},x_{n+2},f(x_n,x_{n+1},x_{n+2})$ and find eigenvalues?

For the function $G(\underline{y}_n)=(x_{n+1},x_{n+2},f(x_n,x_{n+1},x_{n+2})=\underline{y}_{n+1}$ The jacobian is:? $$Dg(\underline{y}_n) = \left(\begin{array}{lll} 0 & 1 & 0 \\ 0 & 0 ...
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0answers
150 views

System of first order ODEs with coherent sinusoidal time varying coefficient

I have encountered equations of the form $$\frac{{d{\bf{y}}(t)}}{{dt}} = \left( {{A_0} + {A_1}\cos (\omega t)} \right){\bf{y}}(t)$$where ${\bf{y}}$ is a vector and ${{A_0}}$ and ${{A_1}}$ are square ...
3
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1answer
29 views

Topology equivalence in dynamical system

my name is Eric. I've got trouble when proofing that system $\dot{x}=\alpha+x^2+O(x^3)$ is topological equivalence with system $\dot{x}=\alpha+x^2$. I don't understand how to build the homeomorphism ...
0
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1answer
16 views

How to change the variables so $x_{n+3}=f(x_{n},x_{n+1},x_{n+2})$ becomes of the form $g(y_n)=y_{n+1}$?

How to change the variables so $x_{n+3}=f(x_{n},x_{n+1},x_{n+2})$ becomes of the form $g(\underline{y}_n)=\underline{y}_{n+1}$
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0answers
15 views

Flow Notation over Interval

Given a section of the flow $\Phi^t(x_0)$ (for finite $t$), I'd like to denote a subsection of this flow from times $\tau^{i-1}$ to time $\tau^{i}$ using similar notation. I was considering using ...
0
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0answers
27 views

Normal form calculation

I am working on a problem involves 4 dimensional dynamical system. Is there any ready package (for maple ,matlab...) which calculate the normal form of nonlinear continuous dynamical systems? The ...
1
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1answer
23 views

Closed Form Solutions To Simple Iterated Polynomial Building Blocks

I've been doing some work on fractals and simple iterated polynomials lately. I admit, I've only taken classes up through Calc 2, although I've done a decent bit of reading on many topics over the ...
0
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0answers
12 views

how reducing the number of parameters work? can anyone help me, please.

The number of parameters of differential equations in the first image had been reduced and the solutions are as in the second image. Can anyone explain to me how does the "reducing number of ...
4
votes
1answer
62 views

Dynamical system $x_{n+1} = \frac{1}{2}(x_n - \frac{1}{x_n}) \ \ , \ \ n = 0, 1 , 2,…$

Consider the dynamical system $$ x_{n+1} = \frac{1}{2}(x_n - \frac{1}{x_n}) \ \ , \ \ n = 0, 1 , 2,... $$ So by using the substitution $x_n = \cot(y_n)$, I have found: $$ x_n = \cot(\cot^{-1} ...
0
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0answers
54 views

Points where limit cycle intersects set: $S=\big\{(x_1,x_2)|x_2=0\big\}$ [closed]

I really need some help figuring this out! The system $\dot{x}=f(x)$ with $x(t) \in\mathbb{R^2}$ has a limit cycle that passes trough the set $S=\big\{(x_1,x_2)|x_2=0\big\}$. The ...
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0answers
33 views

For which $r$ is this system dissipative $\ddot{q}+rq^2\dot{q}+\sin(q)\cos(q)=u$

Could someone please help me to understand the following: Having the differential equation: $\ddot{q}+rq^2\dot{q}+\sin(q)\cos(q)=u$ that models the electrical charge $q$ of a particle in an ...
0
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2answers
131 views

approximate vanishing in Pontryagin dual

Let $\{n_k\}\subseteq \mathbb{Z}$ to be any given sequence of integers, and suppose it satisfies the following property: (*) For any $\lambda\in A\subseteq \mathbb{T}$(the unit circle), ...
0
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2answers
34 views

How to modify this bump function so that the “bump” is at $y=1$?

$$f(x) = \begin{cases} e^{-1/(1 - x^2)} & -1 < x < 1\\ 0 & \text{otherwise} \end{cases} $$ I noticed that when I multiply the denominator of the fractional part of this ...
3
votes
2answers
36 views

Lotka-Volterra model with two predators

In this, Lotka-Volterra model, we have two predators: $$\frac{dp}{dt} = ap\left(1-\frac{p}{K}\right) - (b_1q_1+b_2q_2)p$$ $$\frac{dq_1}{dt}=e_1b_1pq_1-m_1q_1$$ ...
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2answers
41 views

How to construct a diffeomorphic function using another function with certain properties

A $C^{\infty}$ function $f(x)$ on the interval $[a, b]$ satisfies the following 3 properties: 1) $f(x) = 1$ for $a \leq x \leq b$ 2) $f(x) = 0$ for $x < \alpha$ and $x > \beta$ where $\alpha ...
0
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1answer
20 views

How to modify a function to meet certain properties?

I want to modify $$B(x) = \left\{ \begin{array}{lr} e^{-\frac{1}{x^2}} & : x > 0\\ 0 & : x \leq 0 \end{array} \right.$$ so that the new function $$C(x) = \left\{ ...
1
vote
1answer
27 views

prove $H(x)=x^\top x$ is constant along solutions of the sytem if $A(x)^\top + A(x)=0$

Could someone please help me to understand the following: Having the differential equation: $\dot{x} = A(x)x$ where $A(x)$ is a real -valued matrix of dimension $n\times n$ How can I prove ...
0
votes
1answer
27 views

Phase portrait in 2 dimensions

I am trying to plot the phase portrait for the system: $\dot{x} = 1+y -e^{-x}$ $\dot{y} = x^3-y$ Now I worked out my eigenvalues to be $\lambda_1 = 2, \lambda_2 = -1$ and these correspond to 2 ...
0
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0answers
48 views

How can we construct Markov partitions for Smale Horseshoe and Solenoid?

I was reading the book Ergodic Theory, Hyperbolic Dynamics and Dimension Theory by Luis Barreira. In Chapter 7, it is asked to construct Markov partitions for the Smale Horseshoe and the solenoid. In ...
0
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0answers
13 views

If $f$ is a diffeomorphism is it true that $NW(f|_{NW(f)})=NW(f)$?

If $f$ is a diffeomorphism is it true that $NW(f|_{NW(f)})=NW(f)$ where $NW(f)$ is the nonwandering set of $f$?
0
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1answer
33 views

looking for a standard theorem for comparison principle for ode

Consider $$ y'_1(t)=f_1(t),\qquad y_1(0)=y_{10}$$ and $$ y'_2(t)=f_2(t),\qquad y_2(0)=y_{20}. $$ If $f_1>f_2,\quad y_{10}>y_{20}$, then $$y_1>y_2.$$ The above is what I was told by my ...