Expansive homoclinic classes

具有跟踪性质的同宿类

Homoclinic classes with shadowing property

本文证明了对于$C^1$通有微分同胚，孤立同宿类具有跟踪性质当且仅当其为双曲基本集。

Homoclinic classes for sectional-hyperbolic sets

We prove that every sectional-hyperbolic Lyapunov stable set contains a nontrivial homoclinic class.

同宿类的李雅普诺夫谱

Lyapunov spectrum of homoclinic classes

研究同宿类C^1泛型微分同胚的测度的李雅普诺夫谱，证明其内部非空，且内部任意向量对应于同宿类上完全支撑的测度的谱。

Collision, explosion and collapse of homoclinic classes

Homoclinic classes of generic $C^1$-diffeomorphisms are maximal transitive sets and pairwise disjoint. We here present a model explaining how two different homoclinic classes may intersect, failing to be disjoint. For that we construct a one-parameter family of diffeomorphisms $(g_s)_{s\in [-1,1]}$ with hyperbolic points $P$ and $Q$ having nontrivial homoclinic classes, such that, for $s>0$, the classes of $P$ and $Q$ are disjoint, for $s<0$, they are equal, and, for $s=0$, their intersection is a saddle-node.

Homoclinic points, atoral polynomials, and periodic points of algebraic Z^d-actions

Cyclic algebraic Z^d-actions are defined by ideals of Laurent polynomials in d commuting variables. Such an action is expansive precisely when the complex variety of the ideal is disjoint from the multiplicative d-torus. For such expansive actions it is known that the limit for the growth rate of periodic points exists and is equal to the entropy of the action. In an earlier paper the authors extended this result to ideals whose variety intersects the d-torus in a finite set. Here we further extend it to the case when the dimension of intersection of the variety with the d-torus is at most d-2…

On the indices of periodic points in $C^1$-generic wild homoclinic classes in dimension three

We study the dynamics of homoclinic classes on three dimensional manifolds under the robust absence of dominated splittings. We prove that if such a homoclinic class contains a volume-expanding periodic point, then, $C^1$-generically, it contains a hyperbolic periodic point whose index (dimension of the unstable manifold) is equal to two.

Homoclinic classes for generic C^1 vector fields

We prove that homoclinic classes for a residual set of C^1 vector fields X on closed n-manifolds are maximal transitive and depend continuously on periodic orbit data. In addition, X does not exhibit cycles formed by homoclinic classes. We also prove that a homoclinic class of X is isolated if and only if it is Omega-isolated, and that it is the intersection of its stable set and its unstable set. All these properties are well known for structurally stable Axiom A vector fields.

Finiteness of homoclinic classes on sectional hyperbolic sets

We study small perturbations of a sectional hyperbolic set of a vector field on a compact manifold. Indeed, we obtain robustly finiteness of homoclinic classes on this scenary. Moreover, since attractor and repeller sets are particular cases of homoclinic classes, this result improve (A. M. López B, Finiteness and existence of attractors and repellers on sectional hyperbolic sets, Discrete and Continuous Dynamical Systems-A 37).

An example of $C^1$-generically wild homoclinic classes with index deficiency

Given a closed smooth four-dimensional manifold, we construct a diffeomorphism that has a homoclinic class whose continuation locally generically satisfies the following condition: it does not admit any kind of dominated splittings whereas any periodic points belonging to it never have unstable index one.

The Entropy Conjecture for Diffeomorphisms away from Tangencies

We prove that every C1 diffeomorphism away from homoclinic tangencies is entropy expansive, with locally uniform expansivity constant. Consequently, such diffeomorphisms satisfy Shub's entropy conjecture: the entropy is bounded from below by the spectral radius in homology. Moreover, they admit principal symbolic extensions, and the topological entropy and metrical entropy vary continuously with the map. In contrast, generic diffeomorphisms with persistent tangencies are not entropy expansive and have no symbolic extensions.

Homoclinic classes and finitude of attractors for vector fields on n-manifolds

A homoclinic class of a vector field is the closure of the transverse homoclinic orbits associated to a hyperbolic periodic orbit. An attractor (a repeller) is a transitive set to which converges every positive (negative) nearby orbit. We show that a generic C1 vector field on a closed n-manifold has either infinitely many homoclinic classes or a finite collection of attractors (repellers) whose basins form an open-dense set. This result gives an approach to a conjecture by Palis. We also prove the existence of a locally residual subset of C1 vector fields on a 5-manifold having finitely many …

Non-hyperbolic ergodic measures for non-hyperbolic homoclinic classes

We prove that for a generic $C^1$-diffeomorphism existence of a homoclinic class with periodic saddles of different indices (dimension of the unstable bundle) implies existence an invariant ergodic non-hyperbolic (one of the Lyapunov exponents is equal to zero) measure of $f$.

Generic bi-Lyapunov stable homoclinic classes

We study, for $C^1$ generic diffeomorphisms, homoclinic classes which are Lyapunov stable both for backward and forward iterations. We prove they must admit a dominated splitting and show that under some hypothesis they must be the whole manifold. As a consequence of our results we also prove that in dimension 2 the class must be the whole manifold and in dimension 3, these classes must have nonempty interior. Many results on Lyapunov stable homoclinic classes for $C^1$-generic diffeomorphisms are also deduced.

流的同宿类：遍历性与SRB测度

Homoclinic classes for flows: ergodicity and SRB measures

本文研究了流中同宿类的遍历性与SRB测度，证明了特定条件下同宿类交集的遍历性，并探讨了正则SRB测度的相关结果。

Hyperbolicity versus non-hyperbolic ergodic measures inside homoclinic classes

We prove that, for $C^1$-generic diffeomorphisms, if a homoclinic class is not hyperbolic, then there is a non-hyperbolic ergodic measure supported on it. This proves a conjecture by Díaz and Gorodetski [28]. We also discuss the conjectured existence of periodic points with different stable dimension in the class.

Hyperbolic periodic points for chain hyperbolic homoclinic classes

In this paper we establish a closing property and a hyperbolic closing property for thin trapped chain hyperbolic homoclinic classes with one dimensional center in partial hyperbolicity setting. Taking advantage of theses properties, we prove that the growth rate of the number of hyperbolic periodic points is equal to the topological entropy. We also obtain that the hyperbolic periodic measures are dense in the space of invariant measures.

Historic behavior in non-hyperbolic homoclinic classes

We show that $C^1$-generically for diffeomorphisms of manifolds of dimension $d\geq3$, a homoclinic class containing saddles of different indices has a residual subset where the orbit of any point has historic behavior.

Transitivity and homoclinic classes for singular-hyperbolic systems

A {\em singular hyperbolic set} is a partially hyperbolic set with singularities (all hyperbolic) and volume expanding central direction \cite{MPP1}. We study connected, singular-hyperbolic, attracting sets with dense closed orbits {\em and only one singularity}. These sets are shown to be transitive for most $C^r$ flows in the Baire's second category sence. In general these sets are shown to be either transitive or the union of two homoclinic classes. In the later case we prove the existence of finitely many homoclinic classes. Our results generalize for singular-hyperbolic systems a well kno…

$\mathcal{C}^2$ 曲面微分同胚中具有大 Lyapunov 指数的测度同宿类的有限性

Finitness of measured homoclinic classes with large Lyapunov exponents for $\mathcal{C}^2$ surface diffeomorphisms

本文证明了 $\mathcal{C}^2$ 曲面微分同胚中具有大 Lyapunov 指数的测度同宿类的有限性，并由此导出系统熵较大时最大熵遍历测度集合的有限性。

Hyperbolicity versus weak periodic orbits inside homoclinic classes

We prove that, for $C^1$-generic diffeomorphisms, if the periodic orbits contained in a homoclinic class $H(p)$ have all their Lyapunov exponents bounded away from 0, then $H(p)$ must be (uniformly) hyperbolic. This is in sprit of the works of the stability conjecture, but with a significant difference that the homoclinic class $H(p)$ is not known isolated in advance, hence the "weak" periodic orbits created by perturbations near the homoclinic class have to be guaranteed strictly inside the homoclinic class. In this sense the problem is of an "intrinsic" nature, and the classical proof of the…

Codimension one generic homoclinic classes with interior

We study generic diffeomorphisms with a homoclinc class with non empty interior and in particular those admitting a codimension one dominated splitting. We prove that if in the finest dominated splitting the extreme subbundles are one dimensional then the diffeomorphism is partially hyperbolic and from this we deduce that the diffeomorphism is transitive.

Non existence of attractors and dynamics around some wild homoclinic classes

We present new examples of generic diffeomorphisms without attractors. Also, we study how these wild classes are accumulated by infinitely many other classes (obtaining that the chain recurrence classes different from the only quasi-attractor are contained in center stable manifolds). The construction relies on some derived from Anosov (DA) constructions and uses strongly the semiconjugacy obtained by these diffeomorphisms. An interesting feature of this examples is that we can show that robustly, they present a unique attractor in the sense of Milnor.

On the intersection of homoclinic classes in intransitive sectional-Anosov flows

We show that if X is a Venice mask (i.e. nontransitive sectional-Anosov flow with dense periodic orbits) supported on a compact 3-manifold, then the omega-limit set of every non-recurrent point in the unstable manifold of some singularity is a closed orbit. In addition, we prove that the intersection of two different homoclinic classes in the maximal invariant set of a sectional-Anosov flow can be decomposed as the disjoint union of, singular points, a non-singular hyperbolic set, and regular points whose alpha-limit set and omega-limit set is formed by singular points or hyperbolic sets.

部分双曲同宿类中的非双曲遍历测度与马蹄

Non-hyperbolic ergodic measures and horseshoes in partially hyperbolic homoclinic classes

针对鲁棒非双曲传递微分同胚，本文证明其同宿类中每个遍历测度（含非双曲情形）均可由双曲集在弱*拓扑与熵意义下逼近。

同步动力系统：其群胚与 $C^*$-代数

Synchronizing Dynamical Systems: their groupoids and $C^*$-algebras

本文提出同步动力系统以推广 Smale 空间，并研究其相关 $C^\ast$-代数，证明其同宿代数含具有类似 Smale 空间同宿代数行为的理想。

Topological entropy of Lorenz-like flows

We use entropy theory as a new tool for studying Lorenz-like classes of flows in any dimension. More precisely, we show that every Lorenz-like class is entropy expansive, and has positive entropy which varies continuously with vector fields. We deduce that every such class contains a transverse homoclinic orbit and, generically, is an attractor.

On the hyperbolicity of $C^1$-generic homoclinic classes

Works of Liao, Mañé, Franks, Aoki and Hayashi characterized lack of hyperbolicity for diffeomorphisms by the existence of weak periodic orbits. In this note we announce a result which can be seen as a local version of these works: for C$^1$-generic diffeomorphism, a homoclinic class either is hyperbolic or contains a sequence of periodic orbits that have a Lyapunov exponent arbitrarily close to 0. Des travaux de Liao, Mañé, Franks, Aoki et Hayashi ont caractérisé le manque d'hyperbolicité des difféomorphismes par l'existence d'orbites périodiques faibles. Dans cette note, nous annonçons un rés…

Expansive algebraic actions of discrete residually finite amenable groups and their entropy

We prove an entropy formula for certain expansive actions of a countable discrete residually finite group $Γ$ by automorphisms of compact abelian groups in terms of Fuglede-Kadison determinants. This extends an earlier result proved by the first author under somewhat more restrictive conditions. The main tools for this generalization are a representation of the $Γ$-action by means of a `fundamental homoclinic point', and the description of entropy in terms of the renormalized logarithmic growth-rate of the set of $Γ_n$-fixed points, where $(Γ_n, n\ge1)$ is a decreasing sequence of finite index…

On the F-expanding of Homoclinic class

We establish a closing property for thin trapped homoclinic classes. Taking advantage of this property, we proved that if the homoclinic class $H(p)$ admits a dominated splitting $T_{H(p)}M=E\oplus_{<}F$, where $E$ is thin trapped (see Definition \ref{Def:TP}) and all periodic points homoclinically related to $p$ are uniformly $F$-expanding at the period (see Definition \ref{Def:expanding}), then $F$ is expanded (see Definition \ref{Def:TP}).

Newhouse phenomenon and homoclinic classes

We show that for a $C^1$ residual subset of diffeomorphisms far away from tangency, every non-trivial chain recurrent class that is accumulated by sources ia a homoclinic class contains periodic points with index 1 and it's the Hausdorff limit of a family of sources.

Super exponential divergence of periodic points for C^1-generic partially hyperbolic homoclinic classes

A diffeomorphism f is called super exponential divergent if for every r>1, the lower limit of #Per_n(f)/r^n diverges to infinity as n tends to infinity, where Per_n(f) is the set of all periodic points of f with period n. This property is stronger than the usual super exponential growth of the number of periodic points. We show that for a three dimensional manifold M, there exists an open subset O of Diff^1(M) such that diffeomorphisms with super exponential divergent property form a dense subset of O in the C^1-topology. A relevant result of non super exponential divergence for diffeomorphism…

同宿类内部具有多重零 Lyapunov 指数的遍历测度

Ergodic measures with multi-zero Lyapunov exponents inside homoclinic classes

本文研究 $C^1$ 泛型微分同胚同宿类中的非双曲遍历测度，证明在指标跨度且缺少相应支配分裂，或中心丛满足周期轨道 Jacobian 条件时，可构造多个中心 Lyapunov 指数为零且支集覆盖整个同宿类的测度。

Abundance of $C^1$-robust homoclinic tangencies

A diffeomorphism $f$ has a $C^1$-robust homoclinic tangency if there is a $C^1$-neighbourhood $\cU$ of $f$ such that every diffeomorphism in $g\in \cU$ has a hyperbolic set $\La_g$, depending continuously on $g$, such that the stable and unstable manifolds of $\La_g$ have some non-transverse intersection. For every manifold of dimension greater than or equal to three, we exhibit a local mechanism (blender-horseshoes) generating diffeomorphisms with $C^1$-robust homoclinic tangencies. Using blender-horseshoes, we prove that homoclinic classes of $C^1$-generic diffeomorphisms containing saddles …

周期测度与部分双曲同宿类

Periodic measures and partially hyperbolic homoclinic classes

本文证明鲁棒环产生的非双曲遍历测度在 C^1 开稠条件下可由周期测度逼近，并刻画一维中心部分双曲系统中遍历测度闭包的凸集结构。

Some properties of surface diffeomorphisms

We obtain some properties of $C^1$ generic surface diffeomorphisms as finiteness of {\em non-trivial} attractors, approximation by diffeomorphisms with only a finite number of {\em hyperbolic} homoclinic classes, equivalence between essential hyperbolicity and the hyperbolicity of all {\em dissipative} homoclinic classes (and the finiteness of spiral sinks). In particular, we obtain the equivalence between finiteness of sinks and finiteness of spiral sinks, abscence of domination in the set of accumulation points of the sinks, and the equivalence between Axiom A and the hyperbolicity of all ho…

秩1流形上测地流的同宿类

Homoclinic classes of geodesic flows on rank 1 manifolds

该研究针对闭光滑黎曼流形上正速度的$C^{1+β}$流，用不可约可数拓扑马尔可夫流编码同宿相关的不变概率，并借助符号动力学证明了Knieper最大熵测度唯一性及Burns等人平衡态唯一性的相关定理。

奇异流的Lyapunov稳定链回复类

Lyapunov stable chain recurrence classes for singular flows

本文证明对于远离同宿相切的C^1通用向量场，非平凡的Lyapunov稳定链回复类必为同宿类，方法是通过C^2向量场逼近及Gibbs F-态的收敛性论证。

The structure of the space of ergodic measures of transitive partially hyperbolic sets

We provide examples of transitive partially hyperbolic dynamics (specific but paradigmatic examples of homoclinic classes) which blend different types of hyperbolicity in the one-dimensional center direction. These homoclinic classes have two disjoint parts: an "exposed" piece which is poorly homoclinically related with the rest and a "core" with rich homoclinic relations. There is an associated natural division of the space of ergodic measures which are either supported on the exposed piece or on the core. We describe the topology of these two parts and show that they glue along nonhyperbolic…

随机扩张测度

Random Expansive Measures

本研究将扩张性概念推广至随机情境，证明了相对正熵与随机扩张测度的关系，得出正相对拓扑熵下$w$-稳定类条件测度为零，并证明存在不变且扩张的概率测度。

On the dominated splitting of Lyapunov stable aperiodic classes

Recent works related to Palis conjecture of J. Yang, S. Crovisier, M. Sambarino and D. Yang showed that any aperiodic class of a $C^1$-generic diffeomorphism far away from homoclinic bifurcations (or homoclinic tangencies) is partially hyperbolic. We show in this paper that, generically, a non-trivial dominated splitting implies partial hyperbolicity for an aperiodic class if it is Lyapunov stable. More precisely, for $C^1$-generic diffeomorphisms, if a Lyapunov stable aperiodic class has a non-trivial dominated splitting $E\oplus F$, then one of the two bundles is hyperbolic (either $E$ is co…

Intransitive sectional-Anosov flows on 3-manifolds

For each $n\in\mathbb{Z}^+$, we show the existence of Venice masks (i.e. intransitive sectional-Anosov flows with dense periodic orbits) containing $n$ equilibria on certain compact 3-manifolds. These examples are characterized because of the maximal invariant set is a finite union of homoclinic classes. Here, the intersection between two different homoclinic classes is contained in the closure of the union of unstable manifolds of the singularities.

Entropy-minimising models of surface diffeomorphisms relative to homoclinic and heteroclinic orbits

In the theory of surface diffeomorphisms relative to homoclinic and heteroclinic orbits, it is possible to compute a one-dimensional representative map for any irreducible isotopy class. The topological entropy of this graph representative is equal to the growth rate of the number of essential Nielsen classes of a given period, and hence is a lower bound for the topological entropy of the diffeomorphism. In this paper, we show that this entropy bound is the infemum of the topological entropies of diffeomorphisms in the isotopy class, and give necessary and sufficient conditions for the infemal…

Steps towards a classification of $C^r$-generic dynamics close to homoclinic points

We present here the first part of a program for a classification of the generic dynamics close to homoclinic and heteroclinic points, in the $C^r$ topologies, $r\geq 1$. This paper only contains announcements and a few sketches of proofs; a forthcoming series of papers will present the proofs in details. The two prototypical examples of non-hyperbolic dynamics are homoclinic tangencies and heterodimensional cycles. Palis conjectured that they actually characterize densely non-hyperbolic dynamics. It is therefore important to understand what happens close to those bifurcations. We generalize cl…

Mixing-like properties for some generic and robust dynamics

We show that the set of Bernoulli measures of an isolated topologically mixing homoclinic class of a generic diffeomorphism is a dense subset of the set of invariant measures supported on the class. For this, we introduce the large periods property and show that this is a robust property for these classes. We also show that the whole manifold is a homoclinic class for an open and dense subset of the set of robustly transitive diffeomorphisms far away from homoclinic tangencies. In particular, using results from Abdenur and Crovisier, we obtain that every diffeomorphism in this subset is robust…

一般 sectional-hyperbolic 链-复发类的三元分类

A trichotomy for generic sectional-hyperbolic chain-recurrent classes

本文研究了 general sectional-hyperbolic 链-复发类的三元分类问题，证明了其在 C^1 意义下的一般性质。

扩张解与无穷远处的边界对于同质N体问题

Expansive solutions and the boundary at infinity for the homogeneous $N$-body problem

研究同质N体问题中由同质牛顿势驱动的扩张解，建立广泛同质指数范围内的半整个扩张运动存在性，推导细化渐近展开，改进增长估计，包括经典牛顿情况。

Robust transitivity and topological mixing for $C^1$-flows

We prove that non-trivial homoclinic classes of $C^r$-generic flows are topologically mixing. This implies that given $Λ$ a non-trivial $C^1$-robustly transitive set of a vector field $X$, there is a $C^1$-perturbation $Y$ of $X$ such that the continuation $Λ_Y$ of $Λ$ is a topologically mixing set for $Y$. In particular, robustly transitive flows become topologically mixing after $C^1$-perturbations. These results generalize a theorem by Bowen on the basic sets of generic Axiom A flows. We also show that the set of flows whose non-trivial homoclinic classes are topologically mixing is \emph{n…

Lyapunov stable chain recurrent classes

We show that for a $C^1$ residual subset of diffeomorphisms far away from homoclinic tangency, the stable manifolds of periodic points cover a dense subset of the ambient manifold. This gives a partial proof to a conjecture of C. Bonatti.

Uniqueness of SRB measures for transitive diffeomorphisms on surfaces

We give a description of ergodic components of SRB measures in terms of ergodic homoclinic classes associated to hyperbolic periodic points. For transitive surface diffeomorphisms, we prove that there exists at most one SRB measure.

Aperiodic chain recurrence classes of $C^1$-generic diffeomorphisms

We consider the space of $C^1$-diffeomorphims equipped with the $C^1$-topology on a three dimensional closed manifold. It is known that there are open sets in which $C^1$-generic diffeomorphisms display uncountably many chain recurrences classes, while only countably many of them may contain periodic orbits. The classes without periodic orbits, called aperiodic classes, are the main subject of this paper. The aim of the paper is to show that aperiodic classes of $C^1$-generic diffeomorphisms can exhibit a variety of topological properties. More specifically, there are $C^1$-generic diffeomorph…

Nonuniform hyperbolicity for C^1-generic diffeomorphisms

We study the ergodic theory of non-conservative C^1-generic diffeomorphisms. First, we show that homoclinic classes of arbitrary diffeomorphisms exhibit ergodic measures whose supports coincide with the homoclinic class. Second, we show that generic (for the weak topology) ergodic measures of C^1-generic diffeomorphisms are nonuniformly hyperbolic: they exhibit no zero Lyapunov exponents. Third, we extend a theorem by Sigmund on hyperbolic basic sets: every isolated transitive set L of any C^1-generic diffeomorphism f exhibits many ergodic hyperbolic measures whose supports coincide with the w…

零熵非周期ergodic测度的稠密性

Denseness of zero entropy aperiodic ergodic measures

研究部分双曲同宿类中零维中心包的C^1-典型微分同胚的稠密性，证明零熵低复杂度测度在相应测度集中的稠密性。

Canonically Codable Points and Irreducible Codings

$M$ is a cpt. Riemannian manifold without boundary, $f\in\mathrm{Diff}^{1+β}(M)$. In [Sarig13], for all $χ>0$, for every small enough $ε>0$, Sarig had first constructed a coding $\widehatπ:\widehatΣ\rightarrow M$ which covers the set of all Lyapunov regular $χ$-hyperbolic points when $\mathrm{dim}M=2$, where $\widehatΣ$ is a topological Markov shift over a locally-finite and countable directed graph. $\widehatπ$ is Hölder continuous, and is finite-to-one on $\widehatΣ^\#:=\{\underline{u}\in\widehatΣ:\exists v,w\text{ s.t. }\#\{i\geq0:u_i=v\}=\infty, \#\{i\leq0:u_i=w\}=\infty\}$; and $\widehatπ…

Entropy of $C^1$ diffeomorphisms without a dominated splitting

A classical construction due to Newhouse creates horseshoes from hyperbolic periodic orbits with large period and weak domination through local $C^1$-perturbations. Our main theorem shows that, when one works in the $C^1$ topology, the entropy of such horseshoes can be made arbitrarily close to an upper bound deriving from Ruelle's inequality, i.e., the sum of the positive Lyapunov exponents (or the same for the inverse diffeomorphism, whichever is smaller). Adapting classical techniques, we use perturbations that are local and can be chosen to preserve volume or symplectic form or a homoclini…