Stochastic stability versus localization in chaotic dynamical systems

We prove stochastic stability of chaotic maps for a general class of Markov random perturbations (including singular ones) satisfying some kind of mixing conditions. One of the consequences of this statement is the proof of Ulam's conjecture about the approximation of the dynamics of a chaotic system by a finite state Markov chain. Conditions under which the localization phenomenon (i.e. stabilization of singular invariant measures) takes place are also considered. Our main tools are the so called bounded variation approach combined with the ergodic theorem of Ionescu-Tulcea and Marinescu, and a random walk argument that we apply to prove the absence of ``traps'' under the action of random perturbations.Comment: 27 pages, LaTe

Multicomponent dynamical systems: SRB measures and phase transitions

We discuss a notion of phase transitions in multicomponent systems and clarify relations between deterministic chaotic and stochastic models of this type of systems. Connections between various definitions of SRB measures are considered as well.Comment: 13 pages, LaTeX 2

Electronically coupled complementary interfaces between perovskite band insulators

Perovskite oxides exhibit a plethora of exceptional electronic properties, providing the basis for novel concepts of oxide-electronic devices. The interest in these materials is even extended by the remarkable characteristics of their interfaces. Studies on single epitaxial connections between the two wide-bandgap insulators LaAlO3 and SrTiO3 have revealed them to be either high-mobility electron conductors or insulating, depending on the atomic stacking sequences. In the latter case they are conceivably positively charged. For device applications, as well as for basic understanding of the interface conduction mechanism, it is important to investigate the electronic coupling of closely-spaced complementary interfaces. Here we report the successful realization of such electronically coupled complementary interfaces in SrTiO3 - LaAlO3 thin film multilayer structures, in which the atomic stacking sequence at the interfaces was confirmed by quantitative transmission electron microscopy. We found a critical separation distance of 6 perovskite unit cell layers, corresponding to approximately 2.3 nm, below which a decrease of the interface conductivity and carrier density occurs. Interestingly, the high carrier mobilities characterizing the separate electron doped interfaces are found to be maintained in coupled structures down to sub-nanometer interface spacing

Bifractality of the Devil's staircase appearing in the Burgers equation with Brownian initial velocity

It is shown that the inverse Lagrangian map for the solution of the Burgers equation (in the inviscid limit) with Brownian initial velocity presents a bifractality (phase transition) similar to that of the Devil's staircase for the standard triadic Cantor set. Both heuristic and rigorous derivations are given. It is explained why artifacts can easily mask this phenomenon in numerical simulations.Comment: 12 pages, LaTe

Out-of-plane magnetic domain structure in a thin film of La0.67Sr0.33MnO3 on SrTiO3 (001) observed by magnetic force microscopy

The room temperature out-of-plane magnetization of epitaxial thin films of La0.67Sr0.33MnO3 on SrTiO3 (001) has been investigated with magnetic force microscopy, using magnetic tips with very small coercivity, relative to the film. A clear magnetic pattern in the form of a checkerboard, with domain dimensions of a few hundred nanometers, was found for the thin, coherently strained films, which is approximately aligned along the maximum strain [110] and [1[overline 1]0] directions in the film. With increasing in-plane applied magnetic field, the magnetic contrast reduces, reflecting the rotation of the magnetization vector into the plane of the film. This process is reversible with the field. The out-of-plane magnetic pattern is not sensitive to rotation of the in-plane field. We attribute the observed out-of-plane magnetization component to an out-of-plane magnetic anisotropy, which is a remainder of the [111] magnetic easy axis in bulk La0.67Sr0.33MnO3 single crystal

Beta-decay branching ratios of 62Ga

Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyvaskyla. 62Ga is one of the heavier Tz = 0, 0+ -> 0+ beta-emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga. The branching ratio obtained, BR= 99.893(24)%, for the super-allowed branch is in agreement with previous measurements and allows to determine the ft value and the universal Ft value for the super-allowed beta decay of 62Ga

Optimized fabrication of high quality La0.67Sr0.33MnO3 thin films considering all essential characteristics

In this article, an overview of the fabrication and properties of high quality La0.67Sr0.33MnO3 (LSMO) thin films is given. A high quality LSMO film combines a smooth surface morphology with a large magnetization and a small residual resistivity, while avoiding precipitates and surface segregation. In literature, typically only a few of these issues are adressed. We therefore present a thorough characterization of our films, which were grown by pulsed laser deposition. The films were characterized with reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, magnetization and transport measurements, x-ray photoelectron spectroscopy and scanning transmission electron microscopy. The films have a saturation magnetization of 4.0 {\mu}B/Mn, a Curie temperature of 350 K and a residual resistivity of 60 {\mu}{\Omega}cm. These results indicate that high quality films, combining both large magnetization and small residual resistivity, were realized. A comparison between different samples presented in literature shows that focussing on a single property is insufficient for the optimization of the deposition process. For high quality films, all properties have to be adressed. For LSMO devices, the thin film quality is crucial for the device performance. Therefore, this research is important for the application of LSMO in devices.Comment: Accepted for publication in Journal of Physics D - Applied Physic

Precision measurement of the half-life and the decay branches of 62Ga

In an experiment performed at the Accelerator Laboratory of the University of Jyvaskyla, the beta-decay half-life of 62Ga has been studied with high precision using the IGISOL technique. A half-life of T1/2 = 116.09(17)ms was measured. Using beta-gamma coincidences, the gamma intensity of the 954keV transition and an upper limit of the beta-decay feeding of the 0+_2 state have been extracted. The present experimental results are compared to previous measurements and their impact on our understanding of the weak interaction is discussed.Comment: 7 pages, 7 figures, submitted to EPJ

Rare events, escape rates and quasistationarity: some exact formulae

We present a common framework to study decay and exchanges rates in a wide class of dynamical systems. Several applications, ranging form the metric theory of continuons fractions and the Shannon capacity of contrained systems to the decay rate of metastable states, are given