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101.
We study the quark mass expansion of the magnetic moments of the nucleon in a chiral effective field theory including nucleons,
pions and delta-resonances as explicit degrees of freedom. We point out that the usual power counting applied so far to this
problem misses important quark mass structures generated via an intermediate isovector M1 nucleon-delta transition. We propose a modified power counting and compare the resulting chiral extrapolation function to
available (quenched) lattice data. The extrapolation is found to work surprisingly well, given that the lattice data result
from rather large quark masses. Our calculation raises the hope that extrapolations of lattice data utilizing chiral effective
field theory might be applicable over a wider range in quark masses than previously thought, and we discuss some open questions
in this context. Furthermore, we observe that within the current lattice data uncertainties the extrapolations presented here
are consistent with the Padé fit ansatz introduced by the Adelaide group a few years ago.
Received: 23 April 2002 / Accepted: 18 July 2002 / Published online: 17 December 2002
RID="c"
ID="c"e-mail: themmert@physik.tu-muenchen.de
RID="d"
ID="d"e-mail: weise@ect.it
Communicated by A. Sch?fer 相似文献
102.
S. J. Liao 《国际流体数值方法杂志》1992,15(5):595-612
Based on regular boundary element method and a kind of linearity invariance under homotopy, a kind of numerical scheme of 2D steady-state Navier-Stokes equation in streamfunction-vorticity formulation is described. The flow inside a square cavity is used to illustrate this numerical scheme. 相似文献
103.
Li Huishi 《数学年刊B辑(英文版)》1994,15(4):463-468
It is proved that for a left Noetherian z-graded ring A,if every finitely generated graded A-module has finite projective dimension(i.e-,A is gr-regular)then every finitely generated A-module has finite projective dimension(i.e.,A is regular).Some applications of this result to filtered rings and some classical cases are also given. 相似文献
104.
对重氢原子进入钯或钛晶体中可能引起常温核聚变的机理探讨与实验研究结果,已在文献[1]中作了报导。后来又对钛阴极材料,在使用前后进行了X射线结构分析。发现在电解过程中发生过“过热”现象的钛阴极材料的晶体结构由原来的密排六方结构转变为立方结构,而没有发生“过热”现象的钛阴极材料的晶体仍然保持电解前的密排六方结构 相似文献
105.
Xie Xiangyun 《东北数学》1995,(3)
OnLattice-orderedReesMatrixSemigroups¥(谢祥云)XieXiangyun(DepartmentofMathematics,LanzhouUniversity,Lanzhou,730000)Abstract:Thep... 相似文献
106.
B. N. Onwuagba 《Il Nuovo Cimento D》1993,15(7):937-944
Summary The attractive short-range component of the interatomic potential screens the conventional Born-Mayer potential in the framework
of the resonance pseudopotential model. The elastic constants are evaluated at the long-wavelength limit of the phonon spectrum
and the obtained results are compared with previous experimental values. The numerical calculations show that the attractive
component of the potential explains the soft modes in this body-centred cubic (b.c.c.) alkaline-earth metal barium. 相似文献
107.
P-正则半群的双序集 总被引:1,自引:0,他引:1
本文刻划了双序集E为某P-正则半群的幂等元双序集的充要条件.所得定理不仅推广了D.Easdown关于带的双序集的结论,而且导出了正则*-半群的幂等元双序集的一个刻划.进而还对P-正则半群的若干特殊情形及向非正则半群的推广进行了讨论. 相似文献
108.
The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe). 相似文献
109.
There are two main contributions influencing the relative line intensities in a hyperfine pattern of a polycrystalline material:
1) Lattice vibrational anisotropy-Goldanskii-Karyagin effect (GKE) and 2) preferred orientation of the crystallites (texture).
We present the results of experiments and computer calculations of the line-intensity ratios for various orientation distributions.
The two competing effects are hard to distinguish from an experimental point of view, and this evaluation should enable one
to appreciate the magnitude of their respective contributions. A variety of textures is selected and discussed: For instance,
the interesting case where the GKE and the texture produce the same effect on the relative line intensities. Generally speaking,
it seems that in many qualitative discussions of quadrupole line asymmetries the influence of texture is underestimated, especially
for small deviations from randomness. Conversely, the asymmetry in the spectra is often explained by making the ad hoc assumption
of a GKE without realizing that this would require an unrealistic lattice vibration anisotropy.
This work was done in partial fulfillment of the requirement for the degree “Dr. rer. nat.”. 相似文献
110.
We present a regular class of exact black hole solutions of the Einstein equations coupled with a nonlinear electrodynamics source. For weak fields the nonlinear electrodynamics becomes the Maxwell theory, and asymptotically the solutions behave as the Reissner–Nordström one. The class is endowed with four parameters, which can be thought of as the mass m, charge q, and a sort of dipole and quadrupole moments and , respectively. For 3, 4, and |q|2s
c
m the corresponding solutions are regular charged black holes. For = 3, they also satisfy the weak energy condition. For = = 0 we recover the Reissner–Nordström singular solution and for = 3, = 4 the family includes a previous regular black hole reported by the authors. 相似文献