4,586 research outputs found
evolution of chiral-odd twist-3 distribution
We study the dependence of the chiral-odd twist-3 distribution
.The anomalous dimension matrix for the corresponding twist-3
operators is calculated in the one-loop level. This study completes the
calculation of the anomalous dimension matrices for all the twist-3
distributions together with the known results for the other twist-3
distributions and . We also have confirmed that in the
large limit the -evolution of is wholely governed by the
lowest eigenvalue of the anomalous dimension matrix which takes a very simple
analytic form as in the case of and .Comment: 16 pages LaTeX, 4 postscript figure
A new description of motion of the Fermionic SO(2N+2) top in the classical limit under the quasi-anticommutation relation approximation
The boson images of fermion SO(2N+1) Lie operators have been given together
with those of SO(2N+2) ones. The SO(2N+1) Lie operators are generators of
rotation in the (2N+1)-dimensional Euclidian space (N: number of
single-particle states of the fermions). The images of fermion
annihilation-creation operators must satisfy the canonical anti-commutation
relations, when they operate on a spinor subspace. In the regular
representation space we use a boson Hamiltonian with Lagrange multipliers to
select out the spinor subspace. Based on these facts, a new description of a
fermionic SO(2N+2) top is proposed. From the Heisenberg equations of motions
for the boson operators, we get the SO(2N+1) self-consistent field (SCF)
Hartree-Bogoliubov (HB) equation for the classical stationary motion of the
fermion top. Decomposing an SO(2N+1) matrix into matrices describing paired and
unpaired modes of fermions, we obtain a new form of the SO(2N+1) SCF equation
with respect to the paired-mode amplitudes. To demonstrate the effectiveness of
the new description based on the bosonization theory, the extended HB
eigenvalue equation is applied to a superconducting toy-model which consists of
a particle-hole plus BCS type interaction. It is solved to reach an interesting
and exciting solution which is not found in the traditional HB eigenvalue
equation, due to the unpaired-mode effects. To complete the new description,
the Lagrange multipliers must be determined in the classical limit. For this
aim a quasi anti-commutation-relation approximation is proposed. Only if a
certain relation between an SO(2N+1) parameter z and the N is satisfied,
unknown parameters k and l in the Lagrange multipliers can be determined
withuout any inconcistency.Comment: 36 pages, no figures, typos corrected, published versio
Moment Restriction-based Econometric Methods: An Overview
Moment restriction-based econometric modelling is a broad class which includes the parametric, semiparametric and nonparametric approaches. Moments and conditional moments themselves are nonparametric quantities. If a model is specified in part up to some finite dimensional parameters, this will provide semiparametric estimates or tests. If we use the score to construct moment restrictions to estimate finite dimensional parameters, this yields maximum likelihood (ML) estimates. Semiparametric or nonparametric settings based on moment restrictions have been the main concern in the literature, and comprise the most important and interesting topics. The purpose of this special issue on “Moment Restriction-based Econometric Methods†is to highlight some areas in which novel econometric methods have contributed significantly to the analysis of moment restrictions, specifically asymptotic theory for nonparametric regression with spatial data, a control variate method for stationary processes, method of moments estimation and identifiability of semiparametric nonlinear errors-in-variables models, properties of the CUE estimator and a modification with moments, finite sample properties of alternative estimators of coefficients in a structural equation with many instruments, instrumental variable estimation in the presence of many moment conditions, estimation of conditional moment restrictions without assuming parameter identifiability in the implied unconditional moments, moment-based estimation of smooth transition regression models with endogenous variables, a consistent nonparametric test for nonlinear causality, and linear programming-based estimators in simple linear regression.robustness;testing;estimation;model misspecification;moment restrictions;parametric;semiparametric and nonparametric methods
Role of Water Film in Weathering of Porous Rhyolite under Water Unsaturated Condition
AbstractTo study weathering behavior under water-unsaturated conditions, flow-through dissolution experiments using a porous rhyolite were performed under both saturated and unsaturated conditions. When water was passed into a dried rock core, water saturation rapidly increased to 0.3 in 2hours, and then reached 0.4 in 6 days. The proportion of the reactive surface area under the unsaturated condition to that under the saturated condition, Auns/As, was 0.46 after 1 day and increased to 0.90 in 6 days. Because Auns/As was always greater than water saturation, the surfaces of air- filled pores seemed to be wetted with a water film and dissolved. The water film thickness was estimated to be 2–3nm. The reason for Auns/As < 1 may be that the flushing efficiency of dissolved elements in the water film was not enough to keep the concentration far from equilibrium, and thereby the dissolution rate in the water film was decreased
Scaling Theory of Antiferromagnetic Heisenberg Ladder Models
The antiferromagnetic Heisenberg model on multi-leg ladders is
investigated. Criticality of the ground-state transition is explored by means
of finite-size scaling. The ladders with an even number of legs and those with
an odd number of legs are distinguished clearly. In the former, the energy gap
opens up as , where is the strength of the
antiferromagnetic inter-chain coupling. In the latter, the critical phase with
the central charge extends over the whole region of .Comment: 12 pages with 9 Postscript figures. To appear in J. Phys. A: Math.
Ge
Can the frequency-dependent specific heat be measured by thermal effusion methods?
It has recently been shown that plane-plate heat effusion methods devised for
wide-frequency specific-heat spectroscopy do not give the isobaric specific
heat, but rather the so-called longitudinal specific heat. Here it is shown
that heat effusion in a spherical symmetric geometry also involves the
longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex
Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding
Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster
Within the central 10pc of our Galaxy lies a dense nuclear star cluster
(NSC), and similar NSCs are found in most nearby galaxies. Studying the
structure and kinematics of NSCs reveals the history of mass accretion of
galaxy nuclei. Because the Milky Way (MW) NSC is at a distance of only 8kpc, we
can spatially resolve the MWNSC on sub-pc scales. This makes the MWNSC a
reference object for understanding the formation of all NSCs. We have used the
NIR long-slit spectrograph ISAAC (VLT) in a drift-scan to construct an
integral-field spectroscopic map of the central 9.5 x 8pc of our Galaxy. We use
this data set to extract stellar kinematics both of individual stars and from
the unresolved integrated light spectrum. We present a velocity and dispersion
map from the integrated light and model these kinematics using kinemetry and
axisymmetric Jeans models. We also measure CO bandhead strengths of 1,375
spectra from individual stars. We find kinematic complexity in the NSCs radial
velocity map including a misalignment of the kinematic position angle by 9
degree counterclockwise relative to the Galactic plane, and indications for a
rotating substructure perpendicular to the Galactic plane at a radius of 20" or
0.8pc. We determine the mass of the NSC within r = 4.2pc to 1.4 x 10^7 Msun. We
also show that our kinematic data results in a significant underestimation of
the supermassive black hole (SMBH) mass. The kinematic substructure and
position angle misalignment may hint at distinct accretion events. This
indicates that the MWNSC grew at least partly by the mergers of massive star
clusters. Compared to other NSCs, the MWNSC is on the compact side of the r_eff
- M_NSC relation. The underestimation of the SMBH mass might be caused by the
kinematic misalignment and a stellar population gradient. But it is also
possible that there is a bias in SMBH mass measurements obtained with
integrated light.Comment: 20 pages, 19 Figures, Accepted for publication in A&
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