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1.
Let the equation be periodic in time, and let the equilibrium x≡0 be a periodic minimizer. If it is hyperbolic, then the set of asymptotic solutions is a smooth curve in the plane ; this is stated by the Stable Manifold Theorem. The result can be extended to nonhyperbolic minimizers provided only that they are isolated and the equation is analytic (Ureña, 2007 [6]). In this paper we provide an example showing that one cannot say the same for C2 equations. Our example is pathological both in a global sense (the global stable manifold is not arcwise connected), and in a local sense (the local stable manifolds are not locally connected and have points which are not accessible from the exterior).  相似文献   

2.
Let M be smooth n-dimensional manifold, fibered over a k-dimensional submanifold B as π:M→B, and ?Λk(M); one can consider the functional on sections φ of the bundle π defined by , with D a domain in B. We show that for k=n−2 the variational principle based on this functional identifies a unique (up to multiplication by a smooth function) nontrivial vector field in M, i.e., a system of ODEs. Conversely, any vector field X on M satisfying for some ?Λn−2(M) admits such a variational characterization. We consider the general case, and also the particular case M=P×R where one of the variables (the time) has a distinguished role; in this case our results imply that any Liouville (volume-preserving) vector field on the phase space P admits a variational principle of the kind considered here.  相似文献   

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This paper is concerned with the study of the number of critical periods of perturbed isochronous centers. More concretely, if X0 is a vector field having an isochronous center of period T0 at the point p and X? is an analytic perturbation of X0 such that the point p is a center for X? then, for a suitable parameterization ξ of the periodic orbits surrounding p, their periods can be written as T(ξ,?)=T0+T1(ξ)?+T2(ξ)?2+?. Firstly we give formulas for the first functions Tl(ξ) that can be used for quite general vector fields. Afterwards we apply them to study how many critical periods appear when we perturb the rigid quadratic isochronous center , inside the class of centers of the quadratic systems or of polynomial vector fields of a fixed degree.  相似文献   

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Let (X,T) be a topological dynamical system and be a sub-additive potential on C(X,R). Let U be an open cover of X. Then for any T-invariant measure μ, let . The topological pressure for open covers U is defined for sub-additive potentials. Then we have a variational principle:
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8.
Let k be a number field with algebraic closure , and let S be a finite set of primes of k, containing all the infinite ones. Consider a Chebyshev dynamical system on P2. Fix the effective divisor D of P2 that is equal to a line nondegenerate on2[−2,2]. Then we will prove that the set of preperiodic points on which are S-integral relative to D is not Zariski dense in P2.  相似文献   

9.
Any continuous map T on a compact metric space X induces in a natural way a continuous map on the space K(X) of all non-empty compact subsets of X. Let T be a homeomorphism on the interval or on the circle. It is proved that the topological entropy of the induced set valued map is zero or infinity. Moreover, the topological entropy of is zero, where C(X) denotes the space of all non-empty compact and connected subsets of X. For general continuous maps on compact metric spaces these results are not valid.  相似文献   

10.
The purpose of this paper is to derive a generalization of Shimura's results concerning Fourier coefficients of Hilbert modular forms of half integral weight over total real number fields in the case of Hilbert-Maass wave forms over algebraic number fields by following the Shimura's method. Employing theta functions, we shall construct the Shimura correspondence Ψτ from Hilbert-Maass wave forms f of half integral weight over algebraic number fields to Hilbert-Maass wave forms of integral weight over algebraic number fields. We shall determine explicitly the Fourier coefficients of in terms of these f. Moreover, under some assumptions about f concerning the multiplicity one theorem with respect to Hecke operators, we shall establish an explicit connection between the square of Fourier coefficients of f and the central value of quadratic twisted L-series associated with the image of f.  相似文献   

11.
For a metric continuum X, we consider the hyperspaces X2 and C(X) of the closed and nonempty subsets of X and of subcontinua of X, respectively, both with the Hausdorff metric. For a given map we investigate the transitivity of the induced maps and . Among other results, we show that if X is a dendrite or a continuum of type λ and is a map, then C(f) is not transitive. However, if X is the Hilbert cube, then there exists a transitive map such that f2 and C(f) are transitive.  相似文献   

12.
For a Banach space B and for a class A of its bounded closed retracts, endowed with the Hausdorff metric, we prove that retractions on elements AA can be chosen to depend continuously on A, whenever nonconvexity of each AA is less than . The key geometric argument is that the set of all uniform retractions onto an α-paraconvex set (in the spirit of E. Michael) is -paraconvex subset in the space of continuous mappings of B into itself. For a Hilbert space H the estimate can be improved to and the constant can be replaced by the root of the equation α+α2+α3=1.  相似文献   

13.
Let G be a graph and be continuous. Denote by P(f), , ω(f) and Ω(f) the set of periodic points, the closure of the set of periodic points, ω-limit set and non-wandering set of f, respectively. In this paper we show that: (1) vω(f) if and only if vP(f) or there exists an open arc L=(v,w) contained in some edge of G such that every open arc U=(v,c)⊂L contains at least 2 points of some trajectory; (2) vω(f) if and only if every open neighborhood of v contains at least r+1 points of some trajectory, where r is the valence of v; (3) ; (4) if , then x has an infinite orbit.  相似文献   

14.
Let P be a not necessarily bounded polycycle of an analytic vector field on an open set of the plane. Suppose that the singularities which appear after desingularization of the vertices of P are formally linearizable. Consider the function T defined by the return time near P. It is shown that the function T and its derivative T′ have asymptotic expansions in and . It is also shown that under some other conditions imposed on the polycycle vertices, the asymptotic expansions of T and T′ converge absolutely and uniformly to these functions, respectively. These results are applied to the polycycles of the analytic vector fields which have a Darboux first integral. In particular, it is obtained that if P is a polycycle of a Hamiltonian vector field with an analytic (polynomial if P is unbounded) Hamiltonian function, T is a nonoscillating function. Another application concerns the nilpotent centers or focus, since the singularities which appear after desingularization of such a singularity have analytic first integrals.  相似文献   

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We prove an integration by parts formula on the law of the reflecting Brownian motion in the positive half line, where B is a standard Brownian motion. In other terms, we consider a perturbation of X of the form Xε=X+εh with h smooth deterministic function and ε>0 and we differentiate the law of Xε at ε=0. This infinitesimal perturbation changes drastically the set of zeros of X for any ε>0. As a consequence, the formula we obtain contains an infinite-dimensional generalized functional in the sense of Schwartz, defined in terms of Hida's renormalization of the squared derivative of B and in terms of the local time of X at 0. We also compute the divergence on the Wiener space of a class of vector fields not taking values in the Cameron-Martin space.  相似文献   

18.
First, we introduce a certain class of piecewise affine elliptic rotation maps on , called the kaleidoscopic maps, and describe its importance.And then, we concentrate our efforts on a special case, when the rotation angle θ of a kaleidoscopic map is , . For the special case, we answer the conjectures regarding the periodicity and the singularity structure of such (kaleidoscopic) dynamics. In the process, we prove the partial riddling of the regular orbits that gives rise to the classification of periodic sets, and estimate the Hausdorff dimension of the singular set.Finally, we study the dynamics of such kaleidoscopic maps restricted within the singular set, and answer conjectures concerning the chaos, the local chaos, and the ergodicity with respect to the normalized Hausdorff measure of the singular set.  相似文献   

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In this paper, we consider projections on minimal norm ideals of B(H) that are represented as the average of two surjective isometries. We describe projections of the form
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