3,507 research outputs found
First-Principles Evaluation of the Dzyaloshinskii--Moriya Interaction
Full text linkWe review recent developments of formulations to calculate the
Dzyaloshinskii--Moriya (DM) interaction from first principles. In particular,
we focus on three approaches. The first one evaluates the energy change due to
the spin twisting by directly calculating the helical spin structure. The
second one employs the spin gauge field technique to perform the derivative
expansion with respect to the magnetic moment. This gives a clear picture that
the DM interaction can be represented as the spin current in the equilibrium
within the first order of the spin-orbit couplings. The third one is the
perturbation expansion with respect to the exchange couplings and can be
understood as the extension of the Ruderman--Kittel--Kasuya--Yosida (RKKY)
interaction to the noncentrosymmetric spin-orbit systems. By calculating the DM
interaction for the typical chiral ferromagnets MnFeGe and
FeCoGe, we discuss how these approaches work in actual systems.Comment: invited review pape
Doppler shift picture of the Dzyaloshinskii--Moriya interaction
Full text linkWe present a physical picture for the emergence of the Dzyaloshinskii--Moriya
(DM) interaction based on the idea of the Doppler shift by an intrinsic spin
current induced by spin--orbit interaction under broken inversion symmetry. The
picture is confirmed by a rigorous effective Hamiltonian theory, which reveals
that the DM coefficient is given by the magnitude of the intrinsic spin
current. The expression is directly applicable to first principles calculations
and clarifies the relation between the interaction and the electronic band
structures. Quantitative agreement with experimental results is obtained for
the skyrmion compounds MnFeGe and FeCoGe.Comment: 5 pages, 4 figures; v2 references adde
Dynamic estimation of emittance growth with tune depression and nonlinear field energy factor during longitudinal bunch compression for heavy ion inertial fusion driver
Get PDFIn general, the radial matched beam is according
to an equilibrium condition, and depends
on the radial (transverse) confinement
force and the ratio of repulsion forces between
the space charge potential and the thermal pressure
[1-3]. During longitudinal bunch compression,
parameters of charged particle beams are
changed, and the beam current is also increased
due to the increase of the charge density..
Ecosystem Studies of the Arctic Ocean with declining Sea ice (ECOARCS/GRENE Arctic)
Get PDF第6回極域科学シンポジウム特別セッション：[S] 北極温暖化とその影響 ―GRENE 北極気候変動プロジェクトと新しい方向性―11月18日（水） 国立極地研究所 2階 大会議
Dynamic estimation of emittance growth with tune depression and nonlinear field energy factor during longitudinal bunch compression for heavy ion inertial fusion driver
Get PDFIn general, the radial matched beam is according
to an equilibrium condition, and depends
on the radial (transverse) confinement
force and the ratio of repulsion forces between
the space charge potential and the thermal pressure
[1-3]. During longitudinal bunch compression,
parameters of charged particle beams are
changed, and the beam current is also increased
due to the increase of the charge density..
Rotating string in doubled geometry with generalized isometries
Full text linkIn this paper, we first construct a globally well-defined non-geometric
background which contains several branes in type II string theory compactified
on a 7-torus. One of these branes is called 5^2_2, which is a codimension-2
object and has a non-trivial monodromy given by a T-duality transformation. The
geometry near the 5^2_2-brane is shown to approach the non-geometric background
constructed in arXiv:1004.2521. We then construct the solution of a fundamental
string rotating along a non-trivial cycle in the 5^2_2 background. Although the
background is not axisymmetric in the usual sense, we show that it is actually
axisymmetric as a doubled geometry by explicitly finding a generalized Killing
vector. We perform a generalized coordinate transformation into a system where
the generalized isometry is manifest, and show that the winding and momentum
charges of the string solution is explicitly conserved in that system.Comment: 32 pages, 5 figures; v2: typos corrected, to appear in Physical
Review D; v3 minor errors fixed, improvements and a reference added to
section 4.
SOLAR-TERRESTRIAL EVENTS IN FEBRUARY-MARCH 1986
Get PDF1989-11A brief summary of significant solar-terrestrial events occurring in February-March 1986 is presented. Unusually high solar-terrestrial activity was observed in early February 1986. A series of large solar flares took place within the active region of NOAA #4711 during the period 3-7 February 1986. A geomagnetic storm which took place at 13:12 UT on 6 February reached its maximum phase through 8-9 February. The minimum Dst of -312 nT was recorded on early 9 February. It took more than a month to show full recovery. This magnetic storm will be a good example to study various terrestrial events in association with high solar-flare activity. March 1986 was another important interval because extensive observations of comet Halley were performed. Large-scale solar wind structures in the minimum activity phase of the sun and their influences on plasma-tail activity of the comet will be of interest.This special issue contains contributed papers presented at the symposium "Solar Terrestrial Events in February-March 1986" (January 19, 1989, Nagoya)departmental bulletin pape
FOREWORD
Get PDF1989-11This special issue contains contributed papers presented at the symposium "Solar Terrestrial Events in February-March 1986" (January 19, 1989, Nagoya)departmental bulletin pape
Cloud optical thickness and effective particle radius derived from transmitted solar radiation measurements : Comparison with cloud radar observations
Get PDFA method is presented for determining the optical thickness and effective particle radius of stratiform clouds containing liquid water drops in the absence of drizzle from transmitted solar radiation measurements. The procedure compares measurements of the cloud transmittance from the ground at water-absorbing and nonabsorbing wavelengths with lookup tables of the transmittance precomputed for plane-parallel, vertically homogeneous clouds. The optical thickness derived from the cloud transmittance may be used to retrieve vertical profiles of cloud microphysics in combination with the radar reflectivity factor. To do this, we also present an algorithm for solving the radar equation with a constraint of the optical thickness at the visible wavelength. Observations of clouds were made in August and September 2003 at Koganei, Tokyo, Japan, using a PREDE i-skyradiometer and a 95-GHz cloud radar Super Polarimetric Ice Crystal Detection and Explication Radar (SPIDER). The optical thickness and effective radius of water clouds were derived from the i-skyradiometer. Then, the vertical profile of the effective radius was retrieved from SPIDER, using the optical thickness determined from the i-skyradiometer. We found that the effective radii derived by using these two instruments were in good agreement
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