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991.
992.
993.
Paul S. Wesson 《Foundations of Physics Letters》2006,19(3):285-291
NAbstract Following fresh attempts to resolve the problem of the energy density of the vacuum, we reconsider the case where the cosmological
constant is derived from a higher-dimensional version of general relativity, and interpret the gauge-dependence of Λ as a
dynamical effect. This leads to a relation between the change in Λ and the line element (action) which is independent of gauge
choices and fundamental constants: dΛds2 = −6. This implies that the (classical) vacuum is unstable, with implications for particle production. 相似文献
994.
We study (relative) zeta regularized determinants of Laplace type operators on compact conic manifolds. We establish gluing formulae for relative zeta regularized determinants. For arbitrary self-adjoint extensions of the Laplace-Beltrami operator, we express the relative ζ-determinants for these as a ratio of the determinants of certain finite matrices. For the self-adjoint extensions corresponding to Dirichlet and Neumann conditions, the formula is particularly simple and elegant. 相似文献
995.
Paul Fabel 《Topology and its Applications》2007,154(3):635-638
With a certain natural topology, the fundamental group of a locally path connected metric space X becomes discrete if and only if X is semilocally simply connected. We include some related material and offer a counterexample to a similar result. 相似文献
996.
Dan Archdeacon C. Paul Bonnington Joanna A. Ellis-Monaghan 《Discrete and Computational Geometry》2007,38(3):573-594
Steinitz's theorem states that a graph is the 1-skeleton of a convex polyhedron if and only if it is 3-connected and
planar. The polyhedron is called a geometric realization of the embedded graph. Its faces are bounded by convex polygons whose
points are coplanar. A map on the torus does not necessarily have such a geometric realization. In this paper we relax the
condition that faces are the convex hull of coplanar points. We require instead that the convex hull of
the points on a face can be projected onto a plane so that the boundary of the convex hull of the projected points is the
image of the boundary of the face. We also require that the interiors of the convex hulls of different faces do not intersect.
Call this an exhibition of the map. A map is polyhedral if the intersection of any two closed faces is simply connected. Our
main result is that every polyhedral toroidal map can be exhibited. As a corollary, every toroidal triangulation has a geometric
realization. 相似文献
997.
Two problems in projectiles are discussed which generate interestingloci. 相似文献
998.
This paper examines the steady state behaviour of a batch arrival queue with two phases of heterogeneous service along and Bernoulli schedule vacation under multiple vacation policy, where after two successive phases service or first vacation the server may go for further vacations until it finds a new batch of customer in the system. We carry out an extensive stationary analysis of the system, including existence of stationary regime, queue size distribution of idle period process, embedded Markov chain steady state distribution of stationary queue size, busy period distribution along with some system characteristics. 相似文献
999.
Russell G Evans Oleksiy V Klymenko Paul D Price Stephen G Davies Christopher Hardacre Richard G Compton 《Chemphyschem》2005,6(3):526-533
Measurements on the diffusion coefficient of the neutral molecule N,N,N',N'-tetramethyl-para-phenylenediamine and the radical cation and dication generated by its one- and two-electron oxidation, respectively, are reported over the range 298-348 K in both acetonitrile and four room temperature ionic liquids (RTILs). Data were collected using single and double potential step chronoamperometry at a gold disk electrode of micrometer dimension, and analysed via fitting to the appropriate analytical expression or, where necessary, to simulation. The variation of diffusion coefficient with temperature was found to occur in an Arrhenius-type manner for all combinations of solute and solvent. For a given ionic liquid, the diffusional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow. In acetonitrile supported with 0.1 M tetrabutylammonium perchlorate, the ratio in diffusion coefficients of the radical cation and dication to the neutral molecule were calculated as 0.89 +/- 0.05 and 0.51 +/- 0.03, respectively. In contrast, amongst the ionic liquids the same ratios were determined to be on average 0.53 +/- 0.04 and 0.33 +/- 0.03. The consequences of this dissimilarity are considered in terms of the modelling of voltammetric data gathered within ionic liquid solvents. 相似文献
1000.