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631.
Properties of an operator representing the dynamical time in the extended parameterization invariant formulation of quantum mechanics are studied. It is shown that this time operator is given by a positive operator measure analogously to the quantities that are known to represent various measurable time operators. The relation between the dynamical time of the extended formulation and the best known example of the system time operator, i.e., for the free one-dimensional particle, is obtained. 相似文献
632.
Isabelle Staude Ivan S. Maksymov Manuel Decker Andrey E. Miroshnichenko Dragomir N. Neshev Chennupati Jagadish Yuri S. Kivshar 《固体物理学:研究快报》2012,6(12):466-468
We realize a new design of tapered Yagi–Uda nanoantennas and experimentally study their far‐field light scattering. We show that in comparison with untapered structures the tapered nanoantennas exhibit broadband resonances featuring a distinct line shape. Our observations are supported by numerical calculations, which further reveal the tapered nanoantenna's wavelength‐dependent optical near‐field confinement. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
633.
Hermite–Hadamard’s type inequalities for convex functions of selfadjoint operators in Hilbert spaces
S.S. Dragomir 《Linear algebra and its applications》2012,436(5):1503-1515
Some Hermite–Hadamard’s type inequalities for convex functions of selfadjoint operators in Hilbert spaces under suitable assumptions for the involved operators are given. Applications in relation with the celebrated Hölder–McCarthy’s inequality for positive operators and Ky Fan’s inequality for real numbers are given as well. 相似文献
634.
Dragomir Ž. Ðoković 《Linear algebra and its applications》2012,437(10):2680-2682
Mirsky proved that, for the existence of a complex matrix with given eigenvalues and diagonal entries, the obvious necessary condition is also sufficient. We generalize this theorem to matrices over any field and provide a short proof. Moreover, we show that there is a unique companion-matrix-type solution for this problem. 相似文献
635.
Sorin Dumitrescu 《Geometriae Dedicata》2012,160(1):71-90
We study locally homogeneous rigid geometric structures on surfaces. We show that a locally homogeneous projective connection on a compact surface is flat. We also show that a locally homogeneous unimodular affine connection ${\nabla}$ on a two dimensional torus is complete and, up to a finite cover, homogeneous. Let ${\nabla}$ be a unimodular real analytic affine connection on a real analytic compact connected surface M. If ${\nabla}$ is locally homogeneous on a nontrivial open set in M, we prove that ${\nabla}$ is locally homogeneous on all of M. 相似文献
636.
Fischer R Träger D Neshev DN Sukhorukov AA Krolikowski W Denz C Kivshar YS 《Physical review letters》2006,96(2):023905
We demonstrate theoretically and experimentally a novel type of localized beam supported by the combined effects of total internal and Bragg reflection in nonlinear two-dimensional square periodic structures. Such localized states exhibit strong anisotropy in their mobility properties, being highly mobile in one direction and trapped in the other, making them promising candidates for optical routing in nonlinear lattices. 相似文献
637.
Bastea S 《Physical review letters》2006,96(2):028305
We present molecular dynamics simulations of aggregation kinetics in a colloidal suspension modeled as a highly asymmetric binary mixture. Starting from a configuration with largely uncorrelated colloidal particles the system relaxes by coagulation-fragmentation dynamics to a structured state of low-dimensionality clusters with an exponential size distribution. The results show that short-range repulsive interactions alone can give rise to so-called cluster phases. For the present model and probably other, more common colloids, the observed clusters appear to be equilibrium phase fluctuations induced by the entropic intercolloidal attractions. 相似文献
638.
Sorin Popa 《Inventiones Mathematicae》2006,165(2):369-408
We consider crossed product II1 factors
, with G discrete ICC groups that contain infinite normal subgroups with the relative property (T) and σ trace preserving actions
of G on finite von Neumann algebras N that are “malleable” and mixing. Examples are the actions of G by Bernoulli shifts (classical and non-classical) and by Bogoliubov shifts. We prove a rigidity result for isomorphisms of
such factors, showing the uniqueness, up to unitary conjugacy, of the position of the group von Neumann algebra L(G) inside M. We use this result to calculate the fundamental group of M,
, in terms of the weights of the shift σ, for
and other special arithmetic groups. We deduce that for any subgroup S⊂ℝ+* there exist II1 factors M (separable if S is countable or S=ℝ+*) with
. This brings new light to a long standing open problem of Murray and von Neumann. 相似文献
639.
We study compact complex 3-manifolds M admitting a (locally homogeneous) holomorphic Riemannian metric g. We prove the following: (i) If the Killing Lie algebra of g has a non trivial semi-simple part, then it preserves some holomorphic Riemannian metric on M with constant sectional curvature; (ii) If the Killing Lie algebra of g is solvable, then, up to a finite unramified cover, M is a quotient Γ\G, where Γ is a lattice in G and G is either the complex Heisenberg group, or the complex SOL group.
S. Dumitrescu was partially supported by the ANR Grant BLAN 06-3-137237. 相似文献
640.
Error bounds in approximating the Riemann-Stieltjes integral in terms of some new generalised trapezoidal rules are given. Applications for approximating the Riemann integral of a two-function product are provided as well. 相似文献