4,418 research outputs found
Modification of vestibular sensitivity in the rat
Vestibular sensitivity and associated locomotor responses of rats in rotating environmen
Theory of resonant inelastic x-ray scattering at the K edge in LaCuO - Multiple scattering effects -
We develop a theory of resonant inelastic x-ray scattering (RIXS) at the
edge in LaCuO on the basis of the Keldysh Green's function formalism.
In our previous analysis (Phys. Rev. B 71, 035110 (2005)), the scattering by
the core-hole potential was treated within the Born approximation, and a
crude-model density of states was used for the band. We improve the
analysis by taking account of the multiple scattering in Cu3d-O bands and
by using a realistic DOS obtained from a band calculation. The multiple
scattering effect is evaluated with the use of the time representation
developed by Nozi\`eres and De Dominicis. It is found that the multiple
scattering effect makes the -edge peak in the absorption coefficient shift
to the lower energy region as a function of photon energy, that is, the photon
energy required to excite the electron to the -edge peak reduces. It is
also found that the multiple-scattering effect does not change the two-peak
structure in the RIXS spectra but modifies slightly the shape as a function of
energy loss. These findings suggests that the multiple scattering effect could
mainly be included into a renormalization of the core-level energy and partly
justify the Born approximation, leading to a future application to the RIXS in
three-dimensional systems.Comment: revised version with extended discussion, 24 pages, 12 figures,
accepted for PR
Review of Statoconia Formation in Birds and Original Research in Chicks (Gallus domesticus)
This paper reviews published materials on statoconia formation in birds, and emphasizes works dealing with the embryonic chick (Gallus domesticus) saccule and utricule. Histological, biochemical and histochemical aspects of forming statoconial membranes and statoconial crystals of mammals are included. Results from our work with chick embryos permitted us to conclude that statoconia probably do not form by seeding of a subunit around central core. Instead, immature statoconia may emerge already formed, from a segmenting mass of organic material that seems to be secreted by the supporting cells of the saccular and utricular maculae. Crystallization of each statoconium may involve seeding of multiple subunits around many nucleation centers in the organic matrix. Following these processes, calcium (sometimes granular) attaches to immature statoconia and become subsequently incorporated between the fibrils of the organic matrix starting at the peripheral zone and advancing toward the central core. Our transmission electron microscopy findings, histochemistry and X-ray microanalysis complements of other investigators, who used chicks with light microscopic studies. These results agree with the notion that the secretion of an organic matrix constitutes the first step toward the formation of the statoconial membrane and statoconia. We show ultra-structurally how statoconia may be assembled from the organic matrix before they acquire their characteristic geometric shapes
Analysis of resonant inelastic x-ray scattering at the edge in NiO
We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the Ni
edge in an antiferromagnetic insulator NiO by applying the theory developed
by the present authors. It is based on the Keldysh Green's function formalism,
and treats the core-hole potential in the intermediate state within the Born
approximation. We calculate the single-particle energy bands within the
Hartree-Fock approximation on the basis of the multi-orbital tight-binding
model. Using these energy bands together with the density of states from
an ab initio band structure calculation, we calculate the RIXS intensities as a
function of energy loss. By taking account of electron correlation within the
random phase approximation (RPA), we obtain quantitative agreement with the
experimental RIXS spectra, which consist of prominent two peaks around 5 eV and
8 eV, and the former shows considerable dispersion while the latter shows no
dispersion. We interpret the peaks as a result of a band-to-band transition
augmented by the RPA correlation.Comment: 11 pages, 10 figures, submitted to PR
Twist Symmetry and Classical Solutions in Open String Field Theory
We construct classical solutions of open string field theory which are not
invariant under ordinary twist operation. From detailed analysis of the moduli
space of the solutions, it turns out that our solutions become nontrivial at
boundaries of the moduli space. The cohomology of the modified BRST operator
and the CSFT potential evaluated by the level truncation method strongly
support the fact that our nontrivial solutions correspond to the closed string
vacuum. We show that the nontrivial solutions are equivalent to the twist even
solution which was found by Takahashi and Tanimoto, and twist invariance of
open string field theory remains after the shift of the classical backgrounds.Comment: 19 pages, 2 figures; v2: errors fixe
X-Ray Magnetic Circular Dichroism at the K edge of Mn3GaC
We theoretically investigate the origin of the x-ray magnetic circular
dichroism (XMCD) spectra at the K edges of Mn and Ga in the ferromagnetic phase
of Mn3GaC on the basis of an ab initio calculation. Taking account of the
spin-orbit interaction in the LDA scheme, we obtain the XMCD spectra in
excellent agreement with the recent experiment. We have analyzed the origin of
each structure, and thus elucidated the mechanism of inducing the orbital
polarization in the p symmetric states. We also discuss a simple sum rule
connecting the XMCD spectra with the orbital moment in the p symmetric states.Comment: 5 pages, 5 figures, accepted for publication in Physical Review
Imaging of Iso-frequency Contours via Resonance-Enhanced Scattering in Near-Pristine Photonic Crystals
The iso-frequency contours of a photonic crystal are important for predicting
and understanding exotic optical phenomena that are not apparent from
high-symmetry band structure visualizations. Here, we demonstrate a method to
directly visualize the iso-frequency contours of high-quality photonic crystal
slabs that shows quantitatively good agreement with numerical results
throughout the visible spectrum. Our technique relies on resonance-enhanced
photon scattering from generic fabrication disorder and surface roughness, so
it can be applied to general photonic and plasmonic crystals, or even
quasi-crystals. We also present an analytical model of the scattering process,
which explains the observation of iso-frequency contours in our technique.
Furthermore, the iso-frequency contours provide information about the
characteristics of the disorder and therefore serve as a feedback tool to
improve fabrication processes.Comment: 8 pages, 5 figure
Interaction Effect in the Kondo Energy of the Periodic Anderson-Hubbard Model
We extend the periodic Anderson model by switching on a Hubbard for the
conduction electrons. The nearly integral valent (Kondo) limit of the
Anderson--Hubbard model is studied with the Gutzwiller variational method. The
new formula for the Kondo energy contains the -dependent chemical
potential of the Hubbard subsystem in the exponent, and the correlation-induced
band narrowing in the prefactor. Both effects tend to suppress the Kondo scale,
which can be understood to result from the blocking of hybridization (this
behaviour is the opposite of that found for Kondo--Hubbard models). At
half-filling, we find a Brinkman--Rice-type transition which leads from a
small-gap Kondo insulator to a Mott insulator.Comment: 4 pages (ReVTeX), submitted for publicatio
A simple construction of fermion measure term in U(1) chiral lattice gauge theories with exact gauge invariance
In the gauge invariant formulation of U(1) chiral lattice gauge theories
based on the Ginsparg-Wilson relation, the gauge field dependence of the
fermion measure is determined through the so-called measure term. We derive a
closed formula of the measure term on the finite volume lattice. The Wilson
line degrees of freedom (torons) of the link field are treated separately to
take care of the global integrability. The local counter term is explicitly
constructed with the local current associated with the cohomologically trivial
part of the gauge anomaly in a finite volume. The resulted formula is very
close to the known expression of the measure term in the infinite volume with a
single parameter integration, and would be useful in practical implementations.Comment: 25 pages, uses JHEP3.cls, the version to appear in JHE
Towards Weyl fermions on the lattice without artefacts
In spite of the breakthrough in non-perturbative chiral gauge theories during
the last decade, the present formulation has stubborn artefacts. Independently
of the fermion representation one is confronted with unwanted CP violation and
infinitely many undetermined weight factors. Renormalization group identifies
the culprit. We demonstrate the procedure on Weyl fermions in a real
representation
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