Poncelet pairs and the Twist Map associated to the Poncelet Billiard

We show that for a fixed curve $K$ and for a family of variables curves $L$, the number of $n$-Poncelet pairs is $\frac{e (n)}{2}$, where $e(n)$ is the number of natural numbers $m$ smaller than $n$ and which satisfies mcd $(m,n)=1$. The curvee $K$ do not have to be part of the family. In order to show this result we consider an associated billiard transformation and a twist map which preserves area. We use Aubry-Mather theory and the rotation number of invariant curves to obtain our main result. In the last section we estimate the derivative of the rotation number of a general twist map using some properties of the continued fraction expansion

C*- Algebras and Thermodynamic Formalism

We present a detailed exposition (for a Dynamical System audience) of the content of the paper: R. Exel and A. Lopes, $C^*$ Algebras, approximately proper equivalence relations and Thermodynamic Formalism, {\it Erg. Theo. and Dyn. Syst.}, Vol 24, pp 1051-1082 (2004). We show only the uniqueness of the \beta-KMS (in a certain C*-Algebra obtained from the operators acting in $L^2$ of a Gibbs invariant probability $\mu$) and its relation with the eigen-probability $\nu_\beta$ for the dual of a certain Ruele operator. We consider an example for a case of Hofbauer type where there exist a Phase transition for the Gibbs state. There is no Phase transition for the KMS state.Comment: version update

Interactions, Specifications, DLR probabilities and the Ruelle Operator in the One-Dimensional Lattice

In this paper, we describe several different meanings for the concept of Gibbs measure on the lattice $\mathbb{N}$ in the context of finite alphabets (or state space). We compare and analyze these "in principle" distinct notions: DLR-Gibbs measures, Thermodynamic Limit and eigenprobabilities for the dual of the Ruelle operator (also called conformal measures). Among other things we extended the classical notion of a Gibbsian specification on $\mathbb{N}$ in such way that the similarity of many results in Statistical Mechanics and Dynamical System becomes apparent. One of our main result claims that the construction of the conformal Measures in Dynamical Systems for Walters potentials, using the Ruelle operator, can be formulated in terms of Specification. We also describe the Ising model, with $1/r^{2+\varepsilon}$ interaction energy, in the Thermodynamic Formalism setting and prove that its associated potential is in Walters space - we present an explicit expression. We also provide an alternative way for obtaining the uniqueness of the DLR-Gibbs measures.Comment: to appear in Discrete and Continuous Dynamical Systems - Series

Functions for relative maximization

We introduce functions for relative maximization in a general context: the beta and alpha applications. After a systematic study concerning regularities, we investigate how to approximate certain values of these functions using periodic orbits. We establish yet that the differential of an alpha application dictates the asymptotic behavior of the optimal trajectories

Correlation Inequalities and Monotonicity Properties of the Ruelle Operator

Let $X = \{1,-1\}^\mathbb{N}$ be the symbolic space endowed with the product order. A Borel probability measure $\mu$ over $X$ is said to satisfy the FKG inequality if for any pair of continuous increasing functions $f$ and $g$ we have $\mu(fg)-\mu(f)\mu(g)\geq 0$. In the first part of the paper we prove the validity of the FKG inequality on Thermodynamic Formalism setting for a class of eigenmeasures of the dual of the Ruelle operator, including several examples of interest in Statistical Mechanics. In addition to deducing this inequality in cases not covered by classical results about attractive specifications our proof has advantage of to be easily adapted for suitable subshifts. We review (and provide proofs in our setting) some classical results about the long-range Ising model on the lattice $\mathbb{N}$ and use them to deduce some monotonicity properties of the associated Ruelle operator and their relations with phase transitions. As is widely known, for some continuous potentials does not exists a positive continuous eigenfunction associated to the spectral radius of the Ruelle operator acting on $C(X)$. Here we employed some ideas related to the involution kernel in order to solve the main eigenvalue problem in a suitable sense - for a class of potentials having low regularity. From this we obtain an explicit tight upper bound for the main eigenvalue (consequently for the pressure) of the Ruelle operator associated to Ising models with $1/r^{2+\varepsilon}$ interaction energy. Extensions of the Ruelle operator to suitable Hilbert Spaces are considered and a theorem solving to the main eigenvalue problem (in a weak sense) is obtained by using the Lions-Lax-Milgram theorem.Comment: 39 page

Selection of measure and a Large Deviation Principle for the general XY model

We consider $(M,d)$ a connected and compact manifold and we denote by $X$ the Bernoulli space $M^{\mathbb{N}}$. The shift acting on $X$ is denoted by $\sigma$. We analyze the general XY model, as presented in a recent paper by A. T. Baraviera, L. M. Cioletti, A. O. Lopes, J. Mohr and R. R. Souza. Denote the Gibbs measure by $\mu_{c}:=h_{c}\nu_{c}$, where $h_{c}$ is the eigenfunction, and, $\nu_{c}$ is the eigenmeasure of the Ruelle operator associated to $cf$. We are going to prove that any measure selected by $\mu_{c}$, as $c\to +\infty$, is a maximizing measure for $f$. We also show, when the maximizing probability measure is unique, that it is true a Large Deviation Principle, with the deviation function $R_{+}^{\infty}=\sum_{j=0}^\infty R_{+} (\sigma^f)$, where $R_{+}:= \beta(f) + V\circ\sigma - V - f$, and, $V$ is any calibrated subaction

On Bertelson-Gromov Dynamical Morse Entropy

In this mainly expository paper we present a detailed proof of several results contained in a paper by M. Bertelson and M. Gromov on Dynamical Morse Entropy. This is an introduction to the ideas presented in that work. Suppose $M$ is compact oriented connected $C^\infty$ manifold of finite dimension. Assume that $f_0 :M \to [0,1]$ is a surjective Morse function. For a given natural number $n$, consider the set $M^n$ and for $x=(x_0,x_1,...,x_{n-1}) \in M^n$, denote $f_n (x) = \frac{1}{n} \, \sum_{j=0}^{n-1} f_0 (x_j).$ The Dynamical Morse Entropy describes for a fixed interval $I\subset [0,1]$ the asymptotic growth of the number of critical points of $f_n$ in $I$, when $n \to \infty$. The part related to the Betti number entropy does not requires the differentiable structure. One can describe generic properties of potentials defined in the $XY$ model of Statistical Mechanics with this machinery

Semiclassical limits, Lagrangian states and coboundary equations

Assume that $f$ is a continuous transformation $f:S^1 \to S^1$. We consider here the cases where $f$ is either the transformation $f(z)=z^2$ or $f$ is a smooth diffeomorphism of the circle $S^1$. Consider a fixed continuous potential $\tau:S^1=[0,1) \to \mathbb{R}$, $\nu\in \mathbb{R}$ and $\varphi:S^1 \to \mathbb{C}$ (a quantum state). The transformation $\hat F_{\nu}$ acting on $\varphi:S^1 \to \mathbb{C}$, $\hat F_{\nu}(\varphi) = \phi$, defined by $\displaystyle \phi(z) = \hat F_{\nu} (\varphi(z)) = \varphi(f(z))e^{i\nu\tau(z)}$ describes a discrete time dynamical evolution of the quantum state $\varphi$. Given $S: \mathbb{R}\to \mathbb{R}$ we define the Lagrangian state $$\varphi_{x}^S(z) = \sum_{k\in\mathbb{Z}} e^{\frac{iS (z-k)}{\hbar}} e^{-\frac{(z-k-x)^2}{4\hbar}}.$$ In this case $\hat F_{\nu}(\varphi_{x}^S(z)) = \sum_{k\in\mathbb{Z}}e^{\frac{iS (f(z)-k)}{\hbar}}e^{-\frac{(f(z)-k-x)^2}{4\hbar}}e^{i\nu\tau(z)}$. Under suitable conditions on $S$ the micro-support of $\varphi^S_x (z)$, when $\hbar \to 0$, is $(x,S'(x))$. One of meanings of the semiclassical limit in Quantum Mechanics is to take $\nu=\frac{1}{\hbar}$ and $\hbar \to 0$. We address the question of finding $S$ such that $\varphi^S_x$ satisfies the property: $\forall x$, we have that $\hat{F}_\nu(\varphi^S_x)$ has micro-support on the graph of $y\to S'(y)$ (which is the micro-support of $\varphi^S_x$). In other words: which $S$ is such that $\hat{F}_\nu$ leaves the micro-support of $\varphi^S_x$ invariant? This is related to a coboundary equation for $\tau$, twist conditions and the boundary of the fat attractor

Generic properties for random repeated quantum iterations

We denote by $M^n$ the set of $n$ by $n$ complex matrices. Given a fixed density matrix $\beta:\mathbb{C}^n \to \mathbb{C}^n$ and a fixed unitary operator $U : \mathbb{C}^n \otimes \mathbb{C}^n \to \mathbb{C}^n \otimes \mathbb{C}^n$, the transformation $\Phi: M^n \to M^n$ $$Q \to \Phi (Q) =\, \text{Tr}_2 (\,U \, ( Q \otimes \beta )\, U^*\,)$$ describes the interaction of $Q$ with the external source $\beta$. The result of this is $\Phi(Q)$. If $Q$ is a density operator then $\Phi(Q)$ is also a density operator. The main interest is to know what happen when we repeat several times the action of $\Phi$ in an initial fixed density operator $Q_0$. This procedure is known as random repeated quantum iterations and is of course related to the existence of one or more fixed points for $\Phi$. In \cite{NP}, among other things, the authors show that for a fixed $\beta$ there exists a set of full probability for the Haar measure such that the unitary operator $U$ satisfies the property that for the associated $\Phi$ there is a unique fixed point $Q_\Phi$. Moreover, there exists convergence of the iterates $\Phi^n (Q_0) \to Q_\Phi$, when $n \to \infty$, for any given $Q_0$ We show here that there is an open and dense set of unitary operators $U: \mathbb{C}^n \otimes \mathbb{C}^n \to \mathbb{C}^n \otimes \mathbb{C}^n$ such that the associated $\Phi$ has a unique fixed point. We will also consider a detailed analysis of the case when $n=2$. We will be able to show explicit results. We consider the $C^0$ topology on the coefficients of $U$. In this case we will exhibit the explicit expression on the coefficients of $U$ which assures the existence of a unique fixed point for $\Phi$. Moreover, we present the explicit expression of the fixed point $Q_\Phi

Entropy and Variational principles for holonomic probabilities of IFS

Associated to a IFS one can consider a continuous map $\hat{\sigma} : [0,1]\times \Sigma \to [0,1]\times \Sigma$, defined by $\hat{\sigma}(x,w)=(\tau_{X_{1}(w)}(x), \sigma(w))$ were $\Sigma=\{0,1, ..., d-1\}^{\mathbb{N}}$, $\sigma: \Sigma \to \Sigma$ is given by$\sigma(w_{1},w_{2},w_{3},...)=(w_{2},w_{3},w_{4}...)$ and $X_{k} : \Sigma \to \{0,1, ..., n-1\}$ is the projection on the coordinate $k$. A $\rho$-weighted system, $\rho \geq 0$, is a weighted system $([0,1], \tau_{i}, u_{i})$ such that there exists a positive bounded function $h : [0,1] \to \mathbb{R}$ and probability $\nu$ on $[0,1]$ satisfying $P_{u}(h)=\rho h, \quad P_{u}^{*}(\nu)=\rho\nu$. A probability $\hat{\nu}$ on $[0,1]\times \Sigma$ is called holonomic for $\hat{\sigma}$ if $\int g \circ \hat{\sigma} d\hat{\nu}= \int g d\hat{\nu}, \forall g \in C([0,1])$. We denote the set of holonomic probabilities by ${\cal H}$. Via disintegration, holonomic probabilities $\hat{\nu}$ on $[0,1]\times \Sigma$ are naturally associated to a $\rho$-weighted system. More precisely, there exist a probability $\nu$ on $[0,1]$ and $u_i, i\in\{0, 1,2,..,d-1\}$ on $[0,1]$, such that is $P_{u}^*(\nu)=\nu$. We consider holonomic ergodic probabilities. For a holonomic probability we define entropy. Finally, we analyze the problem: given $\phi \in \mathbb{B}^{+}$, find the solution of the maximization pressure problem $$p(\phi)=$