4,686 research outputs found

    Shadowing by non uniformly hyperbolic periodic points and uniform hyperbolicity

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    We prove that, under a mild condition on the hyperbolicity of its periodic points, a map gg which is topologically conjugated to a hyperbolic map (respectively, an expanding map) is also a hyperbolic map (respectively, an expanding map). In particular, this result gives a partial positive answer for a question done by A. Katok, in a related context

    Avaliação ecônomica de criadouro de capivaras em sistema semi-intesivo para a região costeira sul do Rio Grande do Sul.

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    Entropy and Poincar\'e recurrence from a geometrical viewpoint

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    We study Poincar\'e recurrence from a purely geometrical viewpoint. We prove that the metric entropy is given by the exponential growth rate of return times to dynamical balls. This is the geometrical counterpart of Ornstein-Weiss theorem. Moreover, we show that minimal return times to dynamical balls grow linearly with respect to its length. Finally, some interesting relations between recurrence, dimension, entropy and Lyapunov exponents of ergodic measures are given.Comment: 11 pages, revised versio

    Benzyl N-(2-hy­droxy-1-{N′-[(1E)-2-hy­droxy­benzyl­idene]hydrazinecarbon­yl}eth­yl)carbamate

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    The mol­ecule of the title compound, C18H19N3O5, adopts a curved arrangement with the terminal benzene rings lying to the same side. The hydroxyl­benzene ring is close to coplanar with the adjacent hydrazine residue [dihedral angle = 11.14 (12)°], an observation which correlates with the presence of an intra­molecular O—H⋯N hydrogen bond. The benzyl ring forms a dihedral angle of 50.84 (13)° with the adjacent carbamate group. A twist in the mol­ecule, at the chiral C atom, is reflected in the dihedral angle of 80.21 (12)° formed between the amide residues. In the crystal, two-dimensional arrays in the ac plane are mediated by O—H⋯O and N—H⋯O hydrogen bonds

    O látex e a borracha da mangabeira.

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    Benzyl N-(1-{N′-[(E)-2-chloro­benzyl­idene]hydrazinecarbon­yl}-2-hy­droxy­eth­yl)carbamate

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    The mol­ecule of the title compound, C18H18ClN3O4, is twisted about the chiral C atom with the dihedral angle between the two amide residues being 87.8 (5)°, but, overall, it can be described as curved, with the benzene rings lying on the same side of the mol­ecule [dihedral angle = 62.8 (4)°]. The conformation about the imine bond [1.294 (7) Å] is E. In the crystal, a two-dimensional array in the ab plane is mediated by O—H⋯O and N—H⋯O hydrogen bonds as well as C—H⋯Cl inter­actions. The layers stack along the c-axis direction, being connected by C—H⋯.π contacts
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