4,676 research outputs found
Spatially Resolved NMR Relaxation Rate in a Noncentrosymmetric Superconductor
We numerically study the spatially-resolved NMR around a single vortex in a
noncentrosymmetric superconductor such as CePt3Si.
The nuclear spin-lattice relaxation rate 1/T1 under the influence of the
vortex core states is calculated for an s+p-wave Cooper pairing state.
The result is compared with that for an s-wave pairing state.Comment: 2 pages; submitted to Proc. of SCES'0
Nuclear Magnetic Relaxation Rate in the Vortex State of a Chiral p-Wave Superconductor
The site-selective nuclear spin-lattice relaxation rate T1^{-1} is
theoretically studied inside a vortex core in a chiral p-wave superconductor
within the framework of the quasiclassical theory of superconductivity. It is
found that T1^{-1} at the vortex center depends on the sense of the chirality
relative to the sense of the magnetic field. Our numerical result shows a
characteristic difference in T1^{-1} between the two chiral states, k_x + i k_y
and k_x - i k_y under the magnetic field.Comment: 2 pages, 2 figures; To be published in Physica C; Proc. of LT23,
Hiroshima (Japan), 20-27 Aug. 200
Effects of mass renormalization on the surface properties of heavy-ion fusion potential
We discuss the effects of fast nuclear excitations on heavy-ion fusion
reactions at energies near and below the Coulomb barrier. Using the fusion of
two Ca nuclei as an example and the inversion method, we show that the
mass renormalization induced by fast nuclear excitations leads to a large
surface diffuseness in the effective potential for heavy-ion fusion reactions.Comment: 13 pages, Late
Sparse Learning over Infinite Subgraph Features
We present a supervised-learning algorithm from graph data (a set of graphs)
for arbitrary twice-differentiable loss functions and sparse linear models over
all possible subgraph features. To date, it has been shown that under all
possible subgraph features, several types of sparse learning, such as Adaboost,
LPBoost, LARS/LASSO, and sparse PLS regression, can be performed. Particularly
emphasis is placed on simultaneous learning of relevant features from an
infinite set of candidates. We first generalize techniques used in all these
preceding studies to derive an unifying bounding technique for arbitrary
separable functions. We then carefully use this bounding to make block
coordinate gradient descent feasible over infinite subgraph features, resulting
in a fast converging algorithm that can solve a wider class of sparse learning
problems over graph data. We also empirically study the differences from the
existing approaches in convergence property, selected subgraph features, and
search-space sizes. We further discuss several unnoticed issues in sparse
learning over all possible subgraph features.Comment: 42 pages, 24 figures, 4 table
Electronic structure and spontaneous internal field around non-magnetic impurities in spin-triplet chiral p-wave superconductors
The electronic structure around an impurity in spin triplet p-wave
superconductors is studied by the Bogoliubov-de Gennes theory on a
tight-binding model, where we have chosen -wave
or -wave states which are
considered to be candidates for the pairing state in SrRuO.
We calculate the spontaneous current and the local density of states around
the impurity and discuss the difference between the two types of pairing.
We propose that it is possible to discriminate the two pairing states by
studying the spatial dependence of the magnetic field around a pair of
impurities.Comment: 4 pages, 4 figure
A two-channel Kondo impurity in the spin-1/2 chain: Consequences for Knight shift experiments
A magnetic impurity in the spin-1/2 chain is a simple realization of the
two-channel Kondo problem since the field theoretical descriptions in the
spin-sector are identical. The correlation functions near the impurity can be
calculated. Using a modified version of the numerical transfer matrix DMRG, we
are able to accurately determine local properties close to the impurity in the
thermodynamic limit. The local susceptibilities (Knight-shifts) show an
interesting behavior in a large range around the impurities. We are able to
make quantitative experimental predictions which would allow to observe
two-channel Kondo physics for the first time directly by doping of spin-1/2
chain compounds.Comment: 2 pages in revtex format including 2 embedded figures (using epsf
Iterative Deconvolution of Quadrupole Split NMR Spectra
We propose a simple method to deconvolute NMR spectra of quadrupolar nuclei
in order to separate the distribution of local magnetic hyperfine field from
the quadrupole splitting. It is based on an iterative procedure which allows to
express the intensity of a single NMR line directly as a linear combination of
the intensities of the total experimental spectrum at a few related
frequencies. This procedure is argued to be an interesting complement to
Fourier transformation since it can lead to a significant noise reduction in
some frequency ranges. This is demonstrated in the case of the 11B-NMR spectrum
in SrCu2(BO3)2 at a field of 31.7 T, where a magnetization plateau at 1/6 of
the saturation has been observed.Comment: 4 pages, 2 figure
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