833 research outputs found
Theory of rotational processes in perpendicular media and application to anisotropy measurement
Numerical and analytical calculations of rotational process in perpendicular recording media are presented. The work supports recent experimental studies that suggest that the measurement of rotational magnetization processes can be used to determine the value of the anisotropy constant. An expression for the rotational magnetization for a noninteracting system is derived taking into account the dispersion of K and the easy-axis orientation. The calculations show that the experiments determine the mean value of H-K, essentially independent of the angular dispersion. A numerical (Monte-Carlo based) micromagnetic model is used to study the effects of magnetostatic and exchange interactions at nonzero temperatures. It is shown that for small values of KV/kT, irreversible magnetization processes take place, which precludes the use of the rotational magnetization method to determine K values. This effect is enhanced by the presence of the magnetostatic interaction. However, the presence of exchange interactions is found to enforce coherent rotation in small fields, reducing the irreversible processes and allowing the determination of H-K. Under these circumstances, it is shown that the exchange does not significantly affect the value of HK, and that a well-defined demagnetization correction of 4piM is appropriate. Finally, a comparison with experimental data gives good agreement for multilayer and granular media and shows the role of domain formation on the rotational magnetization process
Weak Mirror Symmetry of Complex Symplectic Algebras
A complex symplectic structure on a Lie algebra \lie h is an integrable
complex structure with a closed non-degenerate -form. It is
determined by and the real part of the -form. Suppose that
\lie h is a semi-direct product \lie g\ltimes V, and both \lie g and
are Lagrangian with respect to and totally real with respect to .
This note shows that \lie g\ltimes V is its own weak mirror image in the
sense that the associated differential Gerstenhaber algebras controlling the
extended deformations of and are isomorphic. The geometry of
on the semi-direct product \lie g\ltimes V is also shown to be
equivalent to that of a torsion-free flat symplectic connection on the Lie
algebra \lie g. By further exploring a relation between with
hypersymplectic algebras, we find an inductive process to build families of
complex symplectic algebras of dimension from the data of the
-dimensional ones.Comment: 22 page
Double exchange model on triangular lattice: non-coplanar spin configuration and phase transition near quarter filling
Unconventional anomalous Hall effect in frustrated pyrochlore oxides is
originated from spin chirality of non-coplanar localized spins, which can also
be induced by the competition between ferromagnetic (FM) double exchange
interaction and antiferromagnetic superexchange interaction .
Here truncated polynomial expansion method and Monte Carlo simulation are
adopted to investigate the above model on two-dimensional triangular lattice.
We discuss the influence of the range of FM-type spin-spin correlation and
strong electron-spin correlation on the truncation error of spin-spin
correlation near quarter filling. Two peaks of the probability distribution of
spin-spin correlation in non-coplanar spin configuration clearly show that
non-coplanar spin configuration is an intermediate phase between FM and
120-degree spin phase. Near quarter filling, there is a phase transition from
FM into non-coplanar and further into 120-degree spin phase when
continually increases. Finally the effect of temperature on magnetic structure
is discussed.Comment: 10 pages, 5 figure
Evolution equations for quark-gluon distributions in multi-color QCD and open spin chains
We study the scale dependence of the twist-3 quark-gluon parton distributions
using the observation that in the multi-color limit the corresponding QCD
evolution equations possess an additional integral of motion and turn out to be
effectively equivalent to the Schrodinger equation for integrable open
Heisenberg spin chain model. We identify the integral of motion of the spin
chain as a new quantum number that separates different components of the
twist-3 parton distributions. Each component evolves independently and its
scale dependence is governed by anomalous dimension given by the energy of the
spin magnet. To find the spectrum of the QCD induced open Heisenberg spin
magnet we develop the Bethe Ansatz technique based on the Baxter equation. The
solutions to the Baxter equation are constructed using different asymptotic
methods and their properties are studied in detail. We demonstrate that the
obtained solutions provide a good qualitative description of the spectrum of
the anomalous dimensions and reveal a number of interesting properties. We show
that the few lowest anomalous dimensions are separated from the rest of the
spectrum by a finite mass gap and estimate its value.Comment: 52 pages, LaTeX style, 6 figures embedded with epsf.st
Splitting of the pi - rho spectrum in a renormalized light-cone QCD-inspired model
We show that the splitting between the light pseudo-scalar and vector meson
states is due to the strong short-range attraction in the ^1S_0 sector which
makes the pion and the kaon light particles. We use a light-cone QCD-inspired
model of the mass squared operator with harmonic confinement and a Dirac-delta
interaction. We apply a renormalization method to define the model, in which
the pseudo-scalar ground state mass fixes the renormalized strength of the
Dirac-delta interaction.Comment: 9 pages, 2 figures, revtex, accepted by Phys. Rev. D; Corrected typo
Global regularity criterion for the 3D Navier-Stokes equations involving one entry of the velocity gradient tensor
In this paper we provide a sufficient condition, in terms of only one of the
nine entries of the gradient tensor, i.e., the Jacobian matrix of the velocity
vector field, for the global regularity of strong solutions to the
three-dimensional Navier-Stokes equations in the whole space, as well as for
the case of periodic boundary conditions
Higgs-Boson Production Associated with a Single Bottom Quark in Supersymmetric QCD
Due to the enhancement of the couplings between Higgs boson and bottom quarks
in the minimal sypersymmetric standard model (MSSM), the cross section of the
process pp(p\bar{p}) \to h^0b(h^0\bar{b})+X at hadron colliders can be
considerably enhanced. We investigated the production of Higgs boson associated
with a single high-p_T bottom quark via subprocess bg(\bar{b}g) \to
h^0b(h^0\bar{b}) at hadron colliders including the next-to-leading order (NLO)
QCD corrections in MSSM. We find that the NLO QCD correction in the MSSM
reaches 50%-70% at the LHC and 60%-85% at the Fermilab Tevatron in our chosen
parameter space.Comment: accepted by Phys. Rev.
Possible Competing Order-Induced Fermi Arcs in Cuprate Superconductors
We investigate the scenario of competing order (CO) induced Fermi arcs and
pseudogap in cuprate superconductors. For hole-type cuprates, both phenomena as
a function of temperature and doping level can be accounted for if the CO
vanishes at above the superconducting transition and the CO
wave-vector Q is parallel to the antinodal direction. In contrast, the absence
of these phenomena and the non-monotonic d-wave gap in electron-type cuprates
may be attributed to and a CO wave-vector Q parallel to the
nodal direction.Comment: 6 pages and 5 figures, with one figure added in the updated version.
Accepted for publication in Solid State Communications, Fast Communications.
Corresponding author: Nai-Chang Yeh ([email protected]
Competitive inhibition of phytic acid on enzymatic browning of chestnut (Castanea mollissima Blume)
The inhibitory effects of phytic acid (PA) on the browning of fresh-cut chestnuts and the associated mechanisms of PA on polyphenol oxidase (PPO) and peroxidase (POD) activities were investigated. The enzymatic browning of chestnut surfaces and interiors was suppressed by soaking shelled and sliced chestnuts in a PA solution. The specific activities of PPO and POD extracted from chestnuts declined due to inhibition by PA. PA was determined to be a competitive inhibitor of both PPO and POD by Lineweaver-Burk plots. The binding modes of PA with PPO and POD were analysed by AutoDock 4.2
Insulating and Conducting Phases of RbC60
Optical measurements were performed on thin films of RbC,
identified by X-ray diffraction as mostly material. The samples were
subjected to various heat treatments, including quenching and slow cooling from
400K. The dramatic increase in the transmission of the quenched samples, and
the relaxation towards the transmission observed in slow cooled samples
provides direct evidence for the existence of a metastable insulating phase.
Slow cooling results in a phase transition between two electrically conducting
phases.Comment: Minor revisions. Submitted to PRB, RevTeX 3.0 file, 2 postscript
figures included, ir_dop
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