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91.
T. A. Larsson 《Communications in Mathematical Physics》2000,214(2):469-491
Let the DRO (Diffeomorphism, Reparametrization, Observer) algebra?DRO(N) be the extension of diff(N)⊕ diff(1) by its four inequivalent Virasoro-like cocycles. Here diff(N) is the diffeomorphism algebra in N-dimensional spacetime and diff(1) describes reparametrizations of trajectories in the space of tensor-valued p-jets. DRO(N) has a Fock module for each p and each representation of gl(N). Analogous representations for gauge algebras (higher-dimensional Kac–Moody algebras) are also given. The reparametrization
symmetry can be eliminated by a gauge fixing procedure, resulting in previously discovered modules. In this process, two DRO(N) cocycles transmute into anisotropic cocycles for diff(N). Thus the Fock modules of toroidal Lie algebras and their derivation algebras are geometrically explained.
Received: 29 October 1998 / Accepted: 2 May 2000 相似文献
92.
93.
Gaowa Naren Wera Larsson Carlos Benitez-Martin Shiming Li Ezequiel Prez-Inestrosa Bo Albinsson Joakim Andrasson 《Chemical science》2021,12(20):7073
A water soluble diarylethene (DAE) derivative that displays exceptionally intense fluorescence from the colorless open form has been synthesized and characterized using UV/vis spectroscopy and fluorescence microscopy. We show that the bright emission from the open form can be rapidly switched using amplitude modulated red light, that is, by light at wavelengths longer than those absorbed by the fluorescent species. This is highly appealing in any context where undesired background fluorescence disturbs the measurement, e.g., the autofluorescence commonly observed in fluorescence microscopy. We show that this scheme is conveniently applicable using lock-in detection, and that robust amplitude modulation of the probe fluorescence is indeed possible also in cell studies using fluorescence microscopy.A water soluble diarylethene derivative displaying exceptionally bright fluorescence in the open isomeric form has been used for emission amplitude-modulation. We apply this scheme in fluorescence microscopy, aiming to suppress undesired background. 相似文献
94.
95.
S. Rosén R. Peverall J. ter Horst G. Sundström J. Semaniak O. Sundqvist M. Larsson M. de Wilde W.J. van der Zande 《Hyperfine Interactions》1998,115(1-4):201-208
A microchannel plate/CCD-camera particle detector is described that utilises gold strips deposited upon the surface of a MCP
to provide particle arrival time information. The uncertainty in the timing is assessed to be ∼500 ps (FWHM) for a measured
time interval between adjacent strips. The main contribution of which is the result of the slow response time of the CFD compared
to the signal. The application of timing measurement is shown to be of particular benefit in the accurate determination of
product state branching ratios from the dissociative recombination of diatomic ions. Finally, the possibilities of such a
detector are assessed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
96.
A comparison is made between calculations performed nonrelativistically and relativistically for W, Re, Os, Ir, Pt, Au and Hg as substitutional impurities in silicon. The calculations were carried out using the relativistic extended Hückel method. The direct and indirect relativistic effects upon the 5d-like levels and band-gap levels are analysed. 相似文献
97.
T. Björnstad M.J.G. Borge P. Dessagne R.-D. Von Dincklage G.T. Ewan P.G. Hansen A. Huck B. Jonson G. Klotz A. Knipper P.O. Larsson G. Nyman H.L. Ravn C. Richard-Serre K. Riisager D. Schardt G. Walter 《Nuclear Physics A》1985,443(2):283-301
Delayed proton and gamma emissions following the β-decay of 32Ar have been studied. The half-life of 32Ar is 98 ± 2 ms, and the T = 2 analogue state in 32Cl lies at the excitation energy 5036 ± 12 keV. From the intensity of the feeding to this state the proton intensities can be converted to an absolute scale leading to a total proton branching ratio of (43 ± 3)%. From proton-gamma coincidence measurements it emerges that (1.9 ± 0.2)% of the protons lead to the first-excited state in 31S. A level scheme up to 8.75 MeV excitation in 32Cl has been constructed and the Gamow-Teller strength function has been deduced. The result is a renormalization of the axial-vector strength to (49 ± 5)% of the free-nucleon value. 相似文献
98.
Andreas Westerlund Maud Göthe-Lundgren Torbjörn Larsson 《Operations Research Letters》2006,34(3):275-282
We study a class of graph problems which includes as special cases the Held and Karp 1-tree problem, and the minimum spanning tree problem with one degree constraint studied by Glover and Klingman. For another special case, we note a mistake in a paper by Ramesh, Yoon and Karwan. 相似文献
99.
Andreas Westerlund Maud Göthe-Lundgren Torbjörn Larsson 《Discrete Applied Mathematics》2006,154(15):2212-2238
Given an undirected graph with edge costs and both revenues and weights on the vertices, the traveling salesman subtour problem is to find a subtour that includes a depot vertex, satisfies a knapsack constraint on the vertex weights, and that minimizes edge costs minus vertex revenues along the subtour.We propose a decomposition scheme for this problem. It is inspired by the classic side-constrained 1-tree formulation of the traveling salesman problem, and uses stabilized column generation for the solution of the linear programming relaxation. Further, this decomposition procedure is combined with the addition of variable upper bound (VUB) constraints, which improves the linear programming bound. Furthermore, we present a heuristic procedure for finding feasible subtours from solutions to the column generation problems. An extensive experimental analysis of the behavior of the computational scheme is presented. 相似文献
100.