Bi-HKT and bi-Kaehler supersymmetric sigma models

We study CKT (or bi-HKT) N = 4 supersymmetric quantum mechanical sigma models. They are characterized by the usual and the mirror sectors displaying each HKT geometry. When the metric involves isometries, a Hamiltonian reduction is possible. The most natural such reduction with respect to a half of bosonic target space coordinates produces an N = 4 model, related to the twisted Kaehler model due to Gates, Hull and Rocek, but including certain extra F-terms in the superfield action.Comment: 31 pages, minor corrections in the published versio

Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet

We report the coherent manipulation of electron spins in a double quantum dot integrated with a micro-magnet. We performed electric dipole spin resonance experiments in the continuous wave (CW) and pump-and-probe modes. We observed two resonant CW peaks and two Rabi oscillations of the quantum dot current by sweeping an external magnetic field at a fixed frequency. Two peaks and oscillations are measured at different resonant magnetic field, which reflects the fact that the local magnetic fields at each quantum dot are modulated by the stray field of a micro-magnet. As predicted with a density matrix approach, the CW current is quadratic with respect to microwave (MW) voltage while the Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values of two Rabi oscillations directly reflects the MW electric field across the two dots. These results show that the spins on each dot can be manipulated coherently at will by tuning the micro-magnet alignment and MW electric field.Comment: 5 pages, 3 figure

Rotation-induced 3D vorticity in 4He superfluid films adsorbed on a porous glass

Detailed study of torsional oscillator experiments under steady rotation up to 6.28 rad/sec is reported for a 4He superfluid monolayer film formed in 1 micrometer-pore diameter porous glass. We found a new dissipation peak with the height being in proportion to the rotation speed, which is located to the lower temperature than the vortex pair unbinding peak observed in the static state. We propose that 3D coreless vortices ("pore vortices") appear under rotation to explain this new peak. That is, the new peak originates from dissipation close to the pore vortex lines, where large superfluid velocity shifts the vortex pair unbinding dissipation to lower temperature. This explanation is confirmed by observation of nonlinear effects at high oscillation amplitudes.Comment: 4pages, 5figure

Localization of the Grover walks on spidernets and free Meixner laws

A spidernet is a graph obtained by adding large cycles to an almost regular tree and considered as an example having intermediate properties of lattices and trees in the study of discrete-time quantum walks on graphs. We introduce the Grover walk on a spidernet and its one-dimensional reduction. We derive an integral representation of the $n$-step transition amplitude in terms of the free Meixner law which appears as the spectral distribution. As an application we determine the class of spidernets which exhibit localization. Our method is based on quantum probabilistic spectral analysis of graphs.Comment: 32 page

Spectral cross-calibration of VIIRS enhanced vegetation index with MODIS: A case study using year-long global data

© 2015 by the authors; licensee MDPI, Basel, Switzerland. In this study, the Visible Infrared Imaging Radiometer Suite (VIIRS) Enhanced Vegetation Index (EVI) was spectrally cross-calibrated with the Moderate Resolution Imaging Spectroradiometer (MODIS) EVI using a year-long, global VIIRS-MODIS dataset at the climate modeling grid (CMG) resolution of 0.05°-by-0.05°. Our cross-calibration approach was to utilize a MODIS-compatible VIIRS EVI equation derived in a previous study [Obata et al., J. Appl. Remote Sens., vol.7, 2013] and optimize the coefficients contained in this EVI equation for global conditions. The calibrated/optimized MODIS-compatible VIIRS EVI was evaluated using another global VIIRS-MODIS CMG dataset of which acquisition dates did not overlap with those used in the calibration. The calibrated VIIRS EVI showed much higher compatibility with the MODIS EVI than the original VIIRS EVI, where the mean error (MODIS minus VIIRS) and the root mean square error decreased from -0.021 to -0.003 EVI units and from 0.029 to 0.020 EVI units, respectively. Error reductions on the calibrated VIIRS EVI were observed across nearly all view zenith and relative azimuth angle ranges, EVI dynamic range, and land cover types. The performance of the MODIS-compatible VIIRS EVI calibration appeared limited for high EVI values (i.e., EVI > 0.5) due likely to the maturity of the VIIRS dataset used in calibration/optimization. The cross-calibration methodology introduced in this study is expected to be useful for other spectral indices such as the normalized difference vegetation index and two-band EVI

Mantle earthquakes frozen in mylonitized ultramafic pseudotachylytes of spinel-lherzolite facies.

We report a new type of ultramafi c pseudotachylyte that forms a fault- and injection-vein network hosted in the mantle-derived Balmuccia peridotite (Italy). In the fault vein the pseudotachylyte is now deformed and recrystallized into a spinel-lherzolite facies ultramylonite, made of a fi ne (<2 μm) aggregate of olivine, orthopyroxene, clinopyroxene, and spinel, with small amounts of amphibole and dolomite. Electron backscattered diffraction study of the ultramylonite shows a clear crystallographic preferred orientation (CPO) of olivine. The fault vein pseudotachylyte overprints a spinel-lherzolite facies amphibole-bearing mylonite, indicating that shear localization accompanying chemical reaction had taken place in the peridotite before seismic slip produced frictional melting. The occurrence of amphibole in the host mylonite and that of dolomite as well as amphibole in the matrices of ultramylonite and pseudotachylyte may indicate that fl uid was present and had evolved in its composition from H2O-rich to CO2-rich during ductile deformation with metamorphic reactions, which may account for the observed rheological transition from ductile to brittle behavior. The spinel-lherzolite facies assemblage in mylonites, P-T estimations from pyroxene geothermometry and carbonate reactions, and the type of olivine CPO in deformed pseudotachylyte indicate that both the preseismic and the postseismic ductile deformations occurred at ~800 °C and 0.7–1.1 GPa

Conformally Einstein Products and Nearly K\"ahler Manifolds

In the first part of this note we study compact Riemannian manifolds (M,g) whose Riemannian product with R is conformally Einstein. We then consider compact 6--dimensional almost Hermitian manifolds of type W_1+W_4 in the Gray--Hervella classification admitting a parallel vector field and show that (under some regularity assumption) they are obtained as mapping tori of isometries of compact Sasaki-Einstein 5-dimensional manifolds. In particular, we obtain examples of inhomogeneous locally (non-globally) conformal nearly K\"ahler compact manifolds

Electrically driven single electron spin resonance in a slanting Zeeman field

The rapidly rising fields of spintronics and quantum information science have led to a strong interest in developing the ability to coherently manipulate electron spins. Electron spin resonance (ESR) is a powerful technique to manipulate spins that is commonly achieved by applying an oscillating magnetic field. However, the technique has proven very challenging when addressing individual spins. In contrast, by mixing the spin and charge degrees of freedom in a controlled way through engineered non-uniform magnetic fields, electron spin can be manipulated electrically without the need of high-frequency magnetic fields. Here we realize electrically-driven addressable spin rotations on two individual electrons by integrating a micron-size ferromagnet to a double quantum dot device. We find that the electrical control and spin selectivity is enabled by the micro-magnet's stray magnetic field which can be tailored to multi-dots architecture. Our results demonstrate the feasibility of manipulating electron spins electrically in a scalable way.Comment: 25 pages, 6 figure