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1.
C. Waldtmann H.-U. Everts B. Bernu C. Lhuillier P. Sindzingre P. Lecheminant L. Pierre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):501-507
We study the exact low energy spectra of the spin 1/2 Heisenberg antiferromagnet on small samples of the kagomé lattice of up to N=36 sites. In agreement with the conclusions of previous authors, we find that these low energy spectra contradict the hypothesis
of Néel type long range order. Certainly, the ground state of this system is a spin liquid, but its properties are rather
unusual. The magnetic () excitations are separated from the ground state by a gap. However, this gap is filled with nonmagnetic () excitations. In the thermodynamic limit the spectrum of these nonmagnetic excitations will presumably develop into a gapless
continuum adjacent to the ground state. Surprisingly, the eigenstates of samples with an odd number of sites, i.e. samples with an unsaturated spin, exhibit symmetries which could support long range chiral order. We do not know if these
states will be true thermodynamic states or only metastable ones. In any case, the low energy properties of the spin 1/2 Heisenberg
antiferromagnet on the kagomé lattice clearly distinguish this system from either a short range RVB spin liquid or a standard chiral spin liquid. Presumably
they are facets of a generically new state of frustrated two-dimensional quantum antiferromagnets.
Received: 27 November 1997 / Accepted: 29 January 1998 相似文献
2.
We present a stratification by “normal flatness” associated to an analytic mapping, analogous to Hironaka's classical result for analytic spaces. Our construction is based on a generic normal flatness theorem for mappings, proved using techniques concerning the variation of modules of meromorphically parametrized formal power series [1]. The existence of such a stratification was announced by Hironaka [13], but the other claims made in [13] are false. Counterexamples are also presented here. 相似文献
3.
Pierre Angles 《Advances in Applied Clifford Algebras》2005,15(2):291-316
This paper, self-contained, deals with the study of Clifford Algebras associated with n-dimensional skew-hermitian spaces
over the skew field H. The different structures associated with the spaces S of corresponding spinors are given and the natural imbeddings of associated
spinor groups are revealed. 相似文献
4.
This paper is dedicated to the determination of topological S parameters in the transmission line networks. We are especially interested in ideal junctions which consist of short circuit connections. For this type of junctions, it is impossible to deduce the S parameters from the usual impedance or admittance matrices which are not defined in this case. We suggest a method allowing a direct calculation of S. This procedure is described and then carried out for a two wire fork. At last, an experimental application is given for this model. 相似文献
5.
Let Λ be a smooth Lagrangian submanifold of a complex symplectic manifold X. We construct twisted simple holonomic modules along Λ in the stack of deformation-quantization modules on X. 相似文献
6.
We consider Sinai’s random walk in random environment. We prove that infinitely often (i.o.) the size of the concentration neighborhood of this random walk is bounded almost surely. We also get that i.o. the maximal distance between two favorite sites is bounded almost surely. 相似文献
7.
Bissessur H. Charlet G. Gohin E. Simonneau C. Pierre L. Idler W. 《Electronics letters》2003,39(2):192-193
By transmitting 40 channels over 300 km of TeraLight fibre, it is shown that optical differential phase shift keying can be used in 100 GHz-spaced 40 Gbit/s systems, with direct detection and a simple receiving filter. Chromatic dispersion tolerance around 300 ps/nm is also measured, compared to 70 ps/nm for NRZ. 相似文献
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10.
The determination of the enantiomeric purity of 2 or 3-substituted cyclanones, particularly cyclohexanones, is conveniently achieved by derivatisation into cyclic aminals with commercially available (R, R)-1,2-diphenylethylenediamine. The derivatisation procedure is directly done into the NMR tube, instantaneously, and 13C NMR allows an accurate measure of the ee. 相似文献