27,927 research outputs found
Electronic states and magnetic structure at the Co3O4 (110) surface: a first principles study
Tricobalt tetraoxide (Co3O4) is an important catalyst and Co3O4(110) is a
frequently exposed surface in Co3O4 nanomaterials. We employed
Density-functional theory with on-site Coulomb repulsion U term to study the
atomic structures, energetics, magnetic and electronic properties of the two
possible terminations, A and B, of this surface. These calculations predict A
as the stable termination in a wide range of oxygen chemical potentials,
consistent with recent experimental observations. The Co3+ ions do not have a
magnetic moment in the bulk, but become magnetic at the surface, which leads to
surface magnetic orderings different from the one in the bulk. Surface
electronic states are present in the lower half of the bulk band gap and cause
partial metallization of both surface terminations. These states are
responsible for the charge compensation mechanism stabilizing both polar
terminations. The computed critical thickness for polarity compensation is 4
layers
Asymptotic Properties of the Partition Function and Applications in Tail Index Inference of Heavy-Tailed Data
The so-called partition function is a sample moment statistic based on blocks
of data and it is often used in the context of multifractal processes.
It will be shown that its behaviour is strongly influenced by the tail of the
distribution underlying the data either in i.i.d. and weakly dependent cases.
These results will be exploited to develop graphical and estimation methods
for the tail index of a distribution. The performance of the tools proposed is
analyzed and compared with other methods by means of simulations and examples.Comment: 31 pages, 5 figure
Microcausality of spin-induced noncommutative theories
In this brief report, the microcausility of quantum field theory on
spin-induced noncom- mutative spacetime is discussed. It is found that for
spacelike seperation the microcausality is not obeyed by the theory generally.
It means that Lorentz covariance can not guaran- tee microcausality in quantum
field thoery. We also give some comments about quantum field thoeries on such
noncommutative spacetime and the relations between noncommutative spacetime and
causality.Comment: 9 pages, no figur
Relaxed 2-D Principal Component Analysis by Norm for Face Recognition
A relaxed two dimensional principal component analysis (R2DPCA) approach is
proposed for face recognition. Different to the 2DPCA, 2DPCA- and G2DPCA,
the R2DPCA utilizes the label information (if known) of training samples to
calculate a relaxation vector and presents a weight to each subset of training
data. A new relaxed scatter matrix is defined and the computed projection axes
are able to increase the accuracy of face recognition. The optimal -norms
are selected in a reasonable range. Numerical experiments on practical face
databased indicate that the R2DPCA has high generalization ability and can
achieve a higher recognition rate than state-of-the-art methods.Comment: 19 pages, 11 figure
Magnetotransport and spin dynamics in an electron gas formed at oxide interfaces
We investigate the spin-dependent transport properties of a two-dimensional
electron gas formed at oxides' interface in the presence of a magnetic field.
We consider several scenarios for the oxides' properties, including oxides with
co-linear or spiral magnetic and ferroelectric order. For spiral multiferroic
oxides, the magnetoelectric coupling and the topology of the localized magnetic
moments introduce additional, electric field controlled spin-orbit coupling
that affects the magneto-oscillation of the current. An interplay of this
spin-orbit coupling, the exchange field, and of the applied magnetic field
results in a quantum, gate-controlled spin and charge Hall conductance
Large-scale solar wind flow around Saturn's nonaxisymmetric magnetosphere
The interaction between the solar wind and a magnetosphere is fundamental to
the dynamics of a planetary system. Here, we address fundamental questions on
the large-scale magnetosheath flow around Saturn using a 3D magnetohydrodynamic
(MHD) simulation. We find Saturn's polar-flattened magnetosphere to channel
~20% more flow over the poles than around the flanks at the terminator.
Further, we decompose the MHD forces responsible for accelerating the
magnetosheath plasma to find the plasma pressure gradient as the dominant
driver. This is by virtue of a high-beta magnetosheath, and in turn, the
high-MA bow shock. Together with long-term magnetosheath data by the Cassini
spacecraft, we present evidence of how nonaxisymmetry substantially alters the
conditions further downstream at the magnetopause, crucial for understanding
solar wind-magnetosphere interactions such as reconnection and shear
flow-driven instabilities. We anticipate our results to provide a more accurate
insight into the global conditions upstream of Saturn and the outer planets.Comment: Accepted for publication in Journal of Geophysical Journal: Space
Physic
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