37,247 research outputs found
Classification of finite dimensional modules of singly atypical type over the Lie superalgebras sl(m/n)
We classify the finite dimensional indecomposable sl(m/n)-modules with at
least a typical or singly atypical primitive weight. We do this classification
not only for weight modules, but also for generalized weight modules. We obtain
that such a generalized weight module is simply a module obtained by
``linking'' sub-quotient modules of generalized Kac-modules. By applying our
results to sl(m/1), we have in fact completely classified all finite
dimensional sl(m/1)-modules.Comment: 17 pages, Late
Dirac-Schr\"odinger equation for quark-antiquark bound states and derivation of its interaction kerne
The four-dimensional Dirac-Schr\"odinger equation satisfied by
quark-antiquark bound states is derived from Quantum Chromodynamics. Different
from the Bethe-Salpeter equation, the equation derived is a kind of first-order
differential equations of Schr\"odinger-type in the position space. Especially,
the interaction kernel in the equation is given by two different closed
expressions. One expression which contains only a few types of Green's
functions is derived with the aid of the equations of motion satisfied by some
kinds of Green's functions. Another expression which is represented in terms of
the quark, antiquark and gluon propagators and some kinds of proper vertices is
derived by means of the technique of irreducible decomposition of Green's
functions. The kernel derived not only can easily be calculated by the
perturbation method, but also provides a suitable basis for nonperturbative
investigations. Furthermore, it is shown that the four-dimensinal
Dirac-Schr\"odinger equation and its kernel can directly be reduced to rigorous
three-dimensional forms in the equal-time Lorentz frame and the
Dirac-Schr\"odinger equation can be reduced to an equivalent
Pauli-Schr\"odinger equation which is represented in the Pauli spinor space. To
show the applicability of the closed expressions derived and to demonstrate the
equivalence between the two different expressions of the kernel, the t-channel
and s-channel one gluon exchange kernels are chosen as an example to show how
they are derived from the closed expressions. In addition, the connection of
the Dirac-Schr\"odinger equation with the Bethe-Salpeter equation is discussed
Renormalization of the Sigma-Omega model within the framework of U(1) gauge symmetry
It is shown that the Sigma-Omega model which is widely used in the study of
nuclear relativistic many-body problem can exactly be treated as an Abelian
massive gauge field theory. The quantization of this theory can perfectly be
performed by means of the general methods described in the quantum gauge field
theory. Especially, the local U(1) gauge symmetry of the theory leads to a
series of Ward-Takahashi identities satisfied by Green's functions and proper
vertices. These identities form an uniquely correct basis for the
renormalization of the theory. The renormalization is carried out in the
mass-dependent momentum space subtraction scheme and by the renormalization
group approach. With the aid of the renormalization boundary conditions, the
solutions to the renormalization group equations are given in definite
expressions without any ambiguity and renormalized S-matrix elememts are
exactly formulated in forms as given in a series of tree diagrams provided that
the physical parameters are replaced by the running ones. As an illustration of
the renormalization procedure, the one-loop renormalization is concretely
carried out and the results are given in rigorous forms which are suitable in
the whole energy region. The effect of the one-loop renormalization is examined
by the two-nucleon elastic scattering.Comment: 32 pages, 17 figure
Non-volatile resistive switching in dielectric superconductor YBCO
We report on the reversible, nonvolatile and polarity dependent resistive
switching between superconductor and insulator states at the interfaces of a
Au/YBaCuO (YBCO)/Au system. We show that the
superconducting state of YBCO in regions near the electrodes can be reversibly
removed and restored. The possible origin of the switching effect may be the
migration of oxygen or metallic ions along the grain boundaries that control
the intergrain superconducting coupling. Four-wire bulk resistance measurements
reveal that the migration is not restricted to interfaces and produce
significant bulk effects.Comment: 4 pages, 4 figures, corresponding author: C. Acha ([email protected]
TIGER Capacity Building Facility - Phase 1, lessons learnt
The TIGER Capacity Building Facility focused on
closing the technological gap between the users and the
earth observation community within the TIGER
programme. Thirteen projects participated in different
aspects of the capacity building facility:
1. - Basic education, provided via distance learning.
2. - Tailored short courses, selected according to the
research interest and technical background of the
participants.
3. - Research topic oriented supervision, provided by
specialists of the research fields of the participants.
4. - Advanced short courses focusing on selected
earth observation techniques.
Distance education turned to be efficient and cost
effective in the programme - but only for those, who
followed the courses completely. There was a relatively
large percentage that could not complete the studies. The
second and the third type of education were carried out in
ITC, in the Netherlands. The participants evaluated the
courses and the supervision very effective and adequate.
Nevertheless, the follow-up was not always possible.
Two advanced short courses were held in Africa (Cape
Town and Nairobi). One of them addressed the 'scientific
elite' of the EO community, whilst the second focused on
the users of this technology
On indecomposable modules over the Virasoro algebra
It is proved that an indecomposable Harish-Chandra module over the Virasoro
algebra must be (i) a uniformly bounded module, or (ii) a module in Category
, or (iii) a module in Category , or (iv) a module which
contains the trivial module as one of its composition factors.Comment: 5 pages, Latex, to appear in Science in China
Investment efficiency of the new energy industry in China
This paper evaluates the investment efficiency of the new energy industry in China and investigates factors that explain variations in investment efficiency across firms and over time. Applying a four-stage semi-parametric DEA analysis framework to a sample of listed new energy firms over the period 2012-2015, we find that the overall investment efficiency of the new energy industry is relatively low, with an average total technical efficiency of 44%, pure technical efficiency of 48%, and scale efficiency of 90%. We also find that new energy firms’ investment efficiency is affected by both macroeconomic conditions and firm-specific characteristics. Our results are robust and have significant implications for policy makers and firm managers
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