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991.
The turbulent wall shear stress can be influenced through the introduction of spanwise velocity components in the near-wall flow field. The underlying physical mechanisms for the drag reduction still remains to be fully understood. Two distinct wave configurations are analyzed and compared to an unactuated turbulent boundary layer to obtain further inside of the drag reducing mechanism using the dynamic mode decomposition. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
A variety of descent and major-index statistics have been defined for symmetric groups, hyperoctahedral groups, and their generalizations. Typically associated to a pair of such statistics is an Euler–Mahonian distribution, a bivariate polynomial encoding the statistics; such distributions often appear in rational bivariate generating-function identities. We use techniques from polyhedral geometry to establish new multivariate identities generalizing those giving rise to many of the known Euler–Mahonian distributions. The original bivariate identities are then specializations of these multivariate identities. As a consequence of these new techniques we obtain bijective proofs of the equivalence of the bivariate distributions for various pairs of statistics. 相似文献
993.
Matthias Makowski 《Calculus of Variations and Partial Differential Equations》2013,46(1-2):213-252
Let N be a (n + 1)-dimensional globally hyperbolic Lorentzian manifold with a compact Cauchy hypersurface ${\mathcal{S}_{0}}$ and F a curvature function, either the mean curvature H, the root of the second symmetric polynomial ${{\sigma}_{2}=\sqrt{H_{2}}}$ or a curvature function of class (K*), a class of curvature functions which includes the nth root of the Gaussian curvature ${{\sigma}_{n}= K^{\frac{1}{n}}}$ . We consider curvature flows with curvature function F and a volume preserving term and prove long time existence of the flow and exponential convergence of the corresponding graphs in the C ∞-topology to a hypersurface of constant F-curvature, provided there are barriers. Furthermore we examine stability properties and foliations of constant F-curvature hypersurfaces. 相似文献
994.
We consider the mixed boundary value problem, or Zaremba’s problem, for the Laplacian in a bounded Lipschitz domain Ω in R n , n?≥?2. We decompose the boundary $ \partial \Omega= D\cup N$ with D and N disjoint. The boundary between D and N is assumed to be a Lipschitz surface in $\partial \Omega$ . We find an exponent q 0?>?1 so that for p between 1 and q 0 we may solve the mixed problem for L p . Thus, if we specify Dirichlet data on D in the Sobolev space W 1,p (D) and Neumann data on N in L p (N), the mixed problem with data f D and f N has a unique solution and the non-tangential maximal function of the gradient lies in $L^p( \partial \Omega)$ . We also obtain results for p?=?1 when the data comes from Hardy spaces. 相似文献
995.
996.
Matthias Degroote 《The European physical journal. Special topics》2013,218(1):1-70
The Faddeev Random Phase Approximation (FRPA) is a Green’s function method which couples collective degrees of freedom to the single particle motion by resumming an infinite number of Feynman diagrams. The Faddeev technique is applied to describe the two-particle-one-hole (2p1h) and two-hole-one-particle (2h1p) Green’s function in terms of non-interacting propagators and kernels for the particle-particle (pp) and particle-hole (ph) interactions. This results in an equal treatment of the intermediary pp and ph channels. In FRPA both the pp and ph phonons are calculated on the random phase approximation (RPA) level. In this work the equations that lead to the FRPA eigenvalue problem are derived. The method is then applied to atoms, small molecules and the Hubbard model, for which the ground state energy and the ionization energies are calculated. Special attention is directed to the RPA instability in the dissociation limit of diatomic molecules and in the Hubbard model. Several solutions are proposed to overcome this problem. 相似文献
997.
Matthias Egg 《Foundations of Physics》2013,43(9):1124-1135
Delayed-choice experiments in quantum mechanics are often taken to undermine a realistic interpretation of the quantum state. More specifically, Healey has recently argued that the phenomenon of delayed-choice entanglement swapping is incompatible with the view that entanglement is a physical relation between quantum systems. This paper argues against these claims. It first reviews two paradigmatic delayed-choice experiments and analyzes their metaphysical implications. It then applies the results of this analysis to the case of entanglement swapping, showing that such experiments pose no threat to realism about entanglement. 相似文献
998.
999.
Indranil Biswas Steven B. Bradlow Adam Jacob Matthias Stemmler 《Annals of Global Analysis and Geometry》2013,44(3):257-268
Let $X$ be a compact connected Riemann surface and $G$ a connected reductive complex affine algebraic group. Given a holomorphic principal $G$ -bundle $E_G$ over $X$ , we construct a $C^\infty $ Hermitian structure on $E_G$ together with a $1$ -parameter family of $C^\infty $ automorphisms $\{F_t\}_{t\in \mathbb R }$ of the principal $G$ -bundle $E_G$ with the following property: Let $\nabla ^t$ be the connection on $E_G$ corresponding to the Hermitian structure and the new holomorphic structure on $E_G$ constructed using $F_t$ from the original holomorphic structure. As $t\rightarrow -\infty $ , the connection $\nabla ^t$ converges in $C^\infty $ Fréchet topology to the connection on $E_G$ given by the Hermitian–Einstein connection on the polystable principal bundle associated to $E_G$ . In particular, as $t\rightarrow -\infty $ , the curvature of $\nabla ^t$ converges in $C^\infty $ Fréchet topology to the curvature of the connection on $E_G$ given by the Hermitian–Einstein connection on the polystable principal bundle associated to $E_G$ . The family $\{F_t\}_{t\in \mathbb R }$ is constructed by generalizing the method of [6]. Given a holomorphic vector bundle $E$ on $X$ , in [6] a $1$ -parameter family of $C^\infty $ automorphisms of $E$ is constructed such that as $t\rightarrow -\infty $ , the curvature converges, in $C^0$ topology, to the curvature of the Hermitian–Einstein connection of the associated graded bundle. 相似文献
1000.
Esther von Grotthuss Felix Nawa Michael Bolte Hans-Wolfram Lerner Matthias Wagner 《Tetrahedron》2019,75(1):26-30
The 9,10-dimethyl-9,10-dihydro-9,10-diboraanthracene dianion salt Li2[1] instantaneously reacts with the dichalcogens O2(tBu)2, S2Me2, S2(pTol)2, Se2Ph2, and Te2Ph2 under reductive cleavage of the chalcogen–chalcogen bonds to give lithium chalcogenides and neutral 1. In solution, the products are involved in rapid association/dissociation equilibria. In the crystalline state, 1 and Li[O(tBu)] form a diadduct, whereas Li[SMe] gives a B?B-bridged monoadduct. In the three remaining cases, the crystal lattices contain monoadducts of 1 with one tri- and one tetracoordinate boron atom. 相似文献