19,988 research outputs found
On the Application of Gluon to Heavy Quarkonium Fragmentation Functions
We analyze the uncertainties induced by different definitions of the momentum
fraction in the application of gluon to heavy quarkonium fragmentation
function. We numerically calculate the initial fragmentation
functions by using the non-covariant definitions of with finite gluon
momentum and find that these fragmentation functions have strong dependence on
the gluon momentum . As , these fragmentation
functions approach to the fragmentation function in the light-cone definition.
Our numerical results show that large uncertainties remains while the
non-covariant definitions of are employed in the application of the
fragmentation functions. We present for the first time the polarized gluon to
fragmentation functions, which are fitted by the scheme exploited in
this work.Comment: 11 pages, 7 figures;added reference for sec.
Coexistence of coupled magnetic phases in epitaxial TbMnO3 films revealed by ultrafast optical spectroscopy
Ultrafast optical pump-probe spectroscopy is used to reveal the coexistence
of coupled antiferromagnetic/ferroelectric and ferromagnetic orders in
multiferroic TbMnO3 films through their time domain signatures. Our
observations are explained by a theoretical model describing the coupling
between reservoirs with different magnetic properties. These results can guide
researchers in creating new kinds of multiferroic materials that combine
coupled ferromagnetic, antiferromagnetic and ferroelectric properties in one
compound.Comment: Accepted by Appl. Phys. let
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Fault Inductance Based Protection for DC Distribution Systems
The fault protection is a critical element to ensure the reliable and secure operation of DC distribution systems. Most DC distribution systems are tightly coupled systems with low line impedances which may result in fast current increase during a fault. Thus, it is challenging to develop a fast and reliable DC fault protection method. This paper proposes and develops a novel fault inductance based DC protection method without communication between protection units at different locations. The performance of the developed protection algorithm was validated in a Real-Time Hardware-In-the-Loop (RTHIL) test platform. The testing results indicate that the developed inductance based fault location algorithm detects and locates faults with fast speed and high accuracy. Preliminary sensitivity analysis on measurement errors are also conducted to study impacts on accuracy of estimated fault inductance.Center for Electromechanic
Competition of different coupling schemes in atomic nuclei
Shell model calculations reveal that the ground and low-lying yrast states of
the nuclei Pd and Cd are mainly built upon isoscalar
spin-aligned neutron-proton pairs each carrying the maximum angular momentum
J=9 allowed by the shell which is dominant in this nuclear region.
This mode of excitation is unique in nuclei and indicates that the spin-aligned
pair has to be considered as an essential building block in nuclear structure
calculations. In this contribution we will discuss this neutron-proton pair
coupling scheme in detail. In particular, we will explore the competition
between the normal monopole pair coupling and the spin-aligned coupling
schemes. Such a coupling may be useful in elucidating the structure properties
of and neighboring nuclei.Comment: 10 pages, 7 figures, 1 table. Proceedings of the Conference on
Advanced Many-Body and Statistical Methods in Mesoscopic Systems, Constanta,
Romania, June 27th - July 2nd 2011. To appear in Journal of Physics:
Conference Serie
An edge index for the Quantum Spin-Hall effect
Quantum Spin-Hall systems are topological insulators displaying
dissipationless spin currents flowing at the edges of the samples. In
contradistinction to the Quantum Hall systems where the charge conductance of
the edge modes is quantized, the spin conductance is not and it remained an
open problem to find the observable whose edge current is quantized. In this
paper, we define a particular observable and the edge current corresponding to
this observable. We show that this current is quantized and that the
quantization is given by the index of a certain Fredholm operator. This
provides a new topological invariant that is shown to take same values as the
Spin-Chern number previously introduced in the literature. The result gives an
effective tool for the investigation of the edge channels' structure in Quantum
Spin-Hall systems. Based on a reasonable assumption, we also show that the edge
conducting channels are not destroyed by a random edge.Comment: 4 pages, 3 figure
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
For a system with three identical nucleons in a single- shell, the states
can be written as the angular momentum coupling of a nucleon pair and the odd
nucleon. The overlaps between these non-orthonormal states form a matrix which
coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. {\bf
87}, 172501 (2001)]. The propositions they state are related to the eigenvalue
problems of the matrix and dimensions of the associated subspaces. In this
work, the propositions will be proven from the symmetric properties of the
symbols. Algebraic expressions for the dimension of the states, eigenenergies
as well as conditions for conservation of seniority can be derived from the
matrix.Comment: 9 pages, no figur
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