383 research outputs found
4p states and X-Ray Spectroscopy
The 4p states in transition metals and their compounds usually play minor
roles on their physical quantities. Recent development of resonant x-ray
scattering (RXS) at the K-edge of transition metals, however, casts light on
the 4p states, because the signals on orbital and magnetic superlattice spots
are brought about by the modulation in the 4p states. The 4p states are
extending in solids and thereby sensitive to electronic states at neighboring
sites. This characteristic determines the mechanism of RXS that the intensity
on the orbital superlattice spots are mainly generated by the lattice
distortion and those on magnetic superlattice spots by the coupling of the 4p
states with the orbital polarization in the 3d states at neighboring sites.
Taking up typical examples for orbital and magnetic RXS, we demonstrate these
mechanisms on the basis of the band structure calculation. Finally, we study
the MCD spectra at the K-edge, demonstrating that the same mechanism as the
magnetic RXS is working.Comment: 9 pages, 9 figures, submitted to Physica Scripta (comment
Comparison of acoustic properties between natural and synthetic α-quartz crystals
科研費報告書収録論文(課題番号:13555085・基盤研究(B)(2) ・H13~H14/研究代表者:櫛引, 淳一/超高品質人工水晶の超音波マイクロスペクトロスコピー
Theoretical Analysis of Resonant Inelastic X-Ray Scattering Spectra in LaMnO3
We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the K
edge of Mn in the antiferromagnetic insulating manganite LaMnO3. We make use of
the Keldysh-type Green-function formalism, in which the RIXS intensity is
described by a product of an incident-photon-dependent factor and a
density-density correlation function in the 3d states. We calculate the former
factor using the 4p density of states given by an ab initio band structure
calculation and the latter using a multi-orbital tight-binding model. The
ground state of the model Hamiltonian is evaluated within the Hartree-Fock
approximation. Correlation effects are treated within the random phase
approximation (RPA). We obtain the RIXS intensity in a wide range of
energy-loss 2-15 eV. The spectral shape is strongly modified by the RPA
correlation, showing good agreement with the experiments. The
incident-photon-energy dependence also agrees well with the experiments. The
present mechanism that the RIXS spectra arise from band-to-band transitions to
screen the core-hole potential is quite different from the orbiton picture
previously proposed, enabling a comprehensive understanding of the RIXS
spectra.Comment: 20 pages, 10 figures, To be published in PR
Convergence of simulated annealing by the generalized transition probability
We prove weak ergodicity of the inhomogeneous Markov process generated by the
generalized transition probability of Tsallis and Stariolo under power-law
decay of the temperature. We thus have a mathematical foundation to conjecture
convergence of simulated annealing processes with the generalized transition
probability to the minimum of the cost function. An explicitly solvable example
in one dimension is analyzed in which the generalized transition probability
leads to a fast convergence of the cost function to the optimal value. We also
investigate how far our arguments depend upon the specific form of the
generalized transition probability proposed by Tsallis and Stariolo. It is
shown that a few requirements on analyticity of the transition probability are
sufficient to assure fast convergence in the case of the solvable model in one
dimension.Comment: 11 page
Neutral Scalar Higgs Masses and Production Cross Sections in an Extended Supersymmetric Standard Model
Upper bounds on the three neutral scalar Higgs masses are considered in the
supersymmetric standard model with a gauge singlet Higgs field. When the
lightest Higgs is singlet-dominated the second lightest Higgs is shown to lie
near or below the theoretical upper bound on the lightest Higgs mass. We also
consider detectability of these Higgs bosons at a future linear
collider with GeV and show that at least one of the neutral
scalar Higgs has a production cross section larger than 0.04~pb.Comment: Latex 9 pages + 5 figures (not included), KEK-TH-386, KEK preprint
93-204, CHIBA-EP-7
Regulatory T Cells Prevent Liver Fibrosis During HIV Type 1 Infection in a Humanized Mouse Model
Human immunodeficiency virus type 1 (HIV-1) disease is associated with aberrant immune activation, and coinfection with hepatitis C virus (HCV) exacerbates hepatic inflammation and fibrosis. However, the role of HIV-1 infection or host immune modulation in liver pathogenesis is not clearly defined. Here, we report that regulatory T (Treg) cells prevent liver immunopathogenesis during HIV-1 infection in a humanized mouse model. In the absence of Treg cells, HIV-1 infection induced liver fibrosis associated with hepatic stellate cell activation, hepatitis, and liver injury. Our findings provide new insight linking Treg cells and liver immunopathogenesis during HIV-1 infection
Observation of daytime changes in boundary layer on a clear and weak-wind summer day in western suburban of Tokyo
Temperature, relative humidity, and wind conditions were observed on a clear, hot, summer day on 6 August 2019, 07:30–15:30 local time (LT), near the surface and in the boundary layer at the Minami-Osawa Campus of Tokyo Metropolitan University in the western suburb of Tokyo, Japan. Vertical wind profiles were obtained by pilot-balloon observations (PBOs) and unmanned aerial vehicle (UAV) observations. PBOs and surface wind observations revealed a southerly wind in the lower boundary layer from 11:00 LT, which became stronger during 12:30– 15:30 LT. Temperature plateaued at 11:00–13:00 LT near the surface, whereas a sharp peak was observed by the UAV in the surface boundary layer at 11:00 LT. Water-vapor mixing ratios were higher in the afternoon than in the morning, with heavy cloud cover after 14:30 LT. Comparison with PBO data indicated that wind-speed estimations based on UAV flight-attitude information are problematic
Analysis of optical magnetoelectric effect in GaFeO_3
We study the optical absorption spectra in a polar ferrimagnet GaFeO_3. We
consider the E1, E2 and M1 processes on Fe atoms. It is shown that the
magnetoelectric effect on the absorption spectra arises from the E1-M1
interference process through the hybridization between the 4p and 3d states in
the noncentrosymmetry environment of Fe atoms. We perform a microscopic
calculation of the spectra on a cluster model of FeO_6 consisting of an
octahedron of O atoms and an Fe atom displaced from the center with reasonable
values for Coulomb interaction and hybridization. We obtain the magnetoelectric
spectra, which depend on the direction of magnetization, as a function of
photon energy in the optical region 1.0-2.5 eV, in agreement with the
experiment.Comment: 18 pages, 5 figure
Discrete Integrable Systems and Hodograph Transformations Arising from Motions of Discrete Plane Curves
We consider integrable discretizations of some soliton equations associated
with the motions of plane curves: the Wadati-Konno-Ichikawa elastic beam
equation, the complex Dym equation, and the short pulse equation. They are
related to the modified KdV or the sine-Gordon equations by the hodograph
transformations. Based on the observation that the hodograph transformations
are regarded as the Euler-Lagrange transformations of the curve motions, we
construct the discrete analogues of the hodograph transformations, which yield
integrable discretizations of those soliton equations.Comment: 19 page
Equivalence of black hole thermodynamics between a generalized theory of gravity and the Einstein theory
We analyze black hole thermodynamics in a generalized theory of gravity whose
Lagrangian is an arbitrary function of the metric, the Ricci tensor and a
scalar field. We can convert the theory into the Einstein frame via a
"Legendre" transformation or a conformal transformation. We calculate
thermodynamical variables both in the original frame and in the Einstein frame,
following the Iyer--Wald definition which satisfies the first law of
thermodynamics. We show that all thermodynamical variables defined in the
original frame are the same as those in the Einstein frame, if the spacetimes
in both frames are asymptotically flat, regular and possess event horizons with
non-zero temperatures. This result may be useful to study whether the second
law is still valid in the generalized theory of gravity.Comment: 14 pages, no figure
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