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Connection, torsion and curvature are introduced for general (local) Leibniz algebroids. Generalized Bismut connection on is an example leading to a scalar curvature of the form for a closed -form . 相似文献
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Miguel A. Rivera-Castro José G.V. Miranda Daniel O. Cajueiro Roberto F.S. Andrade 《Physica A》2012,391(1-2):170-179
This work uses the concept of Asymmetric Detrended Fluctuation Analysis (A-DFA) to investigate and characterize the occurrence of trend switching in financial series. A-DFA introduces two new roughness exponents, and , which differ from the usual one by separately taking into account contributions to the fluctuations according to whether the local trend is, respectively, upward or downward. The developed methodology requires the evaluation of local values of , and , by restricting the size of the largest window around the value . We show that and behave differently in the neighborhoods of switching points (SPs) where trends change sign. Properly taken differences between shifted local values of , and allow to identify and characterize SP’s. Tests with Weiertrasse functions, isolated peaks, and actual financial series are presented, supporting the validity of the proposed method. 相似文献
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《Journal of Geometry and Physics》2007,57(1):133-156
This paper develops the notion of implicit Lagrangian systems and presents some of their basic properties in the context of Dirac structures. This setting includes degenerate Lagrangian systems and systems with both holonomic and nonholonomic constraints, as well as networks of Lagrangian mechanical systems. The definition of implicit Lagrangian systems with a configuration space makes use of Dirac structures on that are induced from a constraint distribution on as well as natural symplectomorphisms between the spaces , , and . Two illustrative examples are presented; the first is a nonholonomic system, namely a vertical disk rolling on a plane, and the second is an L–C circuit, a degenerate Lagrangian system with holonomic constraints. 相似文献
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《Radiation measurements》2007,42(4-5):644-647
The tetragonal : persistent luminescence materials were prepared by a solid state reaction. The UV excited and persistent luminescence was observed in the green region centred at 535 nm. Both luminescence phenomena are due to the same ion occupying the single site in the host lattice. The codoping usually reduced the persistent luminescence of :, which differs from the : and : materials. Only the ion enhanced slightly the persistent luminescence. With the aid of synchrotron radiation, the band gap energy of : was found to be about 7 eV that is very similar to those of the : materials. Thermoluminescence results suggested that the ions might act as electron traps, but only the TL peaks created by and can be found in the temperature range accessible. Lattice defects (e.g. oxygen vacancies) are also important, since the same main thermoluminescence peak was observed at about with and without codoping. 相似文献
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We define Aeppli and Bott–Chern cohomology for bi-generalized complex manifolds and show that they are finite dimensional for compact bi-generalized Hermitian manifolds. For totally bounded double complexes , we show that the validity of -lemma is equivalent to having the same dimension of several cohomology groups. Some calculations of Bott–Chern cohomology groups of some bi-generalized Hermitian manifolds are given. 相似文献
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Zhao-Yi Zeng Cui-E Hu Ling-Cang Cai Xiang-Rong Chen Fu-Qian Jing 《Solid State Communications》2009,149(47-48):2164-2168
We have performed detailed first-principles calculations to investigate the structural and lattice dynamical properties of NiTi alloy. The calculated static structures consist well with the experimental data and other theoretical results. With quasi harmonic approximation, the phase boundary between B19′ and BCO phases can be described as a five order polynomial . The change of vibrational entropy is /atom at the transition temperature 100 K under zero pressure. 相似文献
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Let be a compact real-analytic manifold, equipped with a real-analytic Riemannian metric , and let be a closed real-analytic 2-form on , interpreted as a magnetic field. Consider the Hamiltonian flow on that describes a charged particle moving in the magnetic field . Following an idea of T. Thiemann, we construct a complex structure on a tube inside by pushing forward the vertical polarization by the Hamiltonian flow “evaluated at time ”. This complex structure fits together with to give a Kähler structure on a tube inside . When , our magnetic complex structure is the adapted complex structure of Lempert–Szőke and Guillemin–Stenzel.We describe the magnetic complex structure in terms of its -tangent bundle, at the level of holomorphic functions, and via a construction using the embeddings of Whitney–Bruhat and Grauert. We describe an antiholomorphic intertwiner between this complex structure and the complex structure induced by , and we give two formulas for local Kähler potentials, which depend on a local choice of vector potential -form for . Finally, we compute the magnetic complex structure explicitly for constant magnetic fields on and . 相似文献
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In this paper, first we introduce a new notion of pseudo anti-commuting for real hypersurfaces in complex two-plane Grassmannians and prove a complete classification theorem, which gives a shrinking Ricci soliton with potential Reeb flow on Hopf real hypersurfaces and a tube over a totally real totally geodesic , in . 相似文献
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Negative thermal expansion materials can experience significant stresses when they are used in composites. Under ambient conditions Zr2(WO4)(PO4)2 displays anisotropic negative thermal expansion (NTE) (, , , at 0 GPa). The effect of hydrostatic pressure on its thermal expansion characteristics was investigated by neutron diffraction between 300 and 60 K at pressures up to 0.3 GPa. No phase transitions were observed in the pressure and temperature range examined. The material was found to have a bulk modulus, B0, of 61.3(8) GPa at ambient temperature, and unlike some other NTE materials, pressure had no detectable effect on thermal expansion (, , , at 0.3 GPa). 相似文献
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Jianwen Wei 《Solid State Communications》2010,150(15-16):777-781
The tunneling conductance in a normal metal/insulator/metal/ mixed wave superconductor (N/I/N/) junction is calculated, where the N/I/N region is a quantum wire. It is found in the single-mode case that the magnitude of the tunneling conductance near zero voltage is enhanced due to the Andreev bound state by quasiparticles with perpendicular and horizontal injection, and the zero-bias conductance varies with ( is the distance from insulating layer to the interface of N/ mixed wave superconductor). Splitting of the zero-bias conductance peak appears in the quantum point contact tunneling spectra for an N/I/N/ junction, and several subgap peaks can split at the same time. On increasing both and the magnitude ratio of the two components for the mixed wave, the subgap resonances exhibit an alternately high and low behavior inside the energy gap. These results are different from those in d-wave and p-wave superconductor junctions. 相似文献
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