Search results for "generalization"
showing 10 items of 250 documents
Phenomenological description of counterflow superfluid turbulence in rotating containers
2004
In this paper a simple equation for the vortex line density describing some of the most relevant observed effects in counterflow superfluid turbulence in ${}^{4}\mathrm{He}$ in the presence of rotation is proposed. This model is based on a generalization of Vinen's equation which incorporates as additional quantity the angular velocity \ensuremath{\Omega}.
Alternative Vinen equation and its extension to rotating counterflow superfluid turbulence
2007
Two alternative Vinen's evolution equations for the vortex line density L in counterflow superfluid turbulence, are physically admissible and lead to analogous results in steady states. In Phys. Rev. B, 69, 094513 (2004) the most used of them was generalized to counterflow superfluid turbulence in rotating containers. Here, the analogous generalization for the alternative Vinen's equation is proposed. Both generalized Vinen's equations are compared with the experimental results, not only in steady-states but also in some unsteady situations. From this analysis follows that the solutions of the alternative Vinen's equation tend significantly faster to the corresponding final steady state val…
Approximate treatment of higher excitations in coupled-cluster theory.
2005
The possibilities for the approximate treatment of higher excitations in coupled-cluster (CC) theory are discussed. Potential routes for the generalization of corresponding approximations to lower-level CC methods are analyzed for higher excitations. A general string-based algorithm is presented for the evaluation of the special contractions appearing in the equations specific to those approximate CC models. It is demonstrated that several iterative and noniterative approximations to higher excitations can be efficiently implemented with the aid of our algorithm and that the coding effort is mostly reduced to the generation of the corresponding formulas. The performance of the proposed and …
Diffusion Process in Quasi-One-Dimensional Structures as Elements of Novel Nanodevices
2012
The effective diffusion coefficient in two-phase one-dimensional model with the periodical distribution of inclusions in the effective medium approximation is calculated and generalization about a quasi-one-dimensional case is formed.
Efficiencies of logical Bell measurements on Calderbank-Shor-Steane codes with static linear optics
2019
We show how the efficiency of a logical Bell measurement (BM) can be calculated for arbitrary Calderbank-Shor-Steane (CSS) codes with the experimentally important constraint of using only transversal static linear-optical BMs on the physical single-photon qubit level. For this purpose, we utilize the codes' description in terms of stabilizers in order to calculate general efficiencies for the loss-free case, but also for specific cases including photon loss. These efficiencies can be, for instance, used for obtaining transmission rates of all-optical quantum repeaters. In the loss-free case, we demonstrate that the important class of CSS codes with identical physical-qubit support for the t…
A generalization of the Carnahan–Starling approach with applications to four- and five-dimensional hard spheres
2018
Abstract Development of good equations of state for hard spheres is an important task in the study of real fluids. In a way consistent with other theoretical results, we generalize the famous Carnahan–Starling approach for arbitrary dimensions and apply it to four- and five-dimensional hard spheres. We obtain simple and integer representations for virial coefficients of lower orders and accurate equations of state. Since theoretically and practically validated, these results improve understanding of hard sphere fluids.
Zur Frage der Charakterisierung stationärer Bewegungen in der Hydrodynamik
1958
Helmholtz andKorteweg propose that the steady motion of a viscous fluid under constant extraneous forces having a single-valued potential dissipates—for any given region and assuming that inertia terms in the dynamic equations can be neglected—less energy than any other motion with the same values of velocity at the boundary.—A generalization of this proposition is here given, and an application discussed. The application deals with the motion of a simple macromolecule model in an inhomogeneous field of flow—a motion caused only by the influence ofStokes' friction.
On the geometry of Killing and conformal tensors
2006
The second order Killing and conformal tensors are analyzed in terms of their spectral decomposition, and some properties of the eigenvalues and the eigenspaces are shown. When the tensor is of type I with only two different eigenvalues, the condition to be a Killing or a conformal tensor is characterized in terms of its underlying almost-product structure. A canonical expression for the metrics admitting these kinds of symmetries is also presented. The space-time cases 1+3 and 2+2 are analyzed in more detail. Starting from this approach to Killing and conformal tensors a geometric interpretation of some results on quadratic first integrals of the geodesic equation in vacuum Petrov-Bel type…
Tree-Loop Duality Relation beyond simple poles
2013
We develop the Tree-Loop Duality Relation for two- and three-loop integrals with multiple identical propagators (multiple poles). This is the extension of the Duality Relation for single poles and multi-loop integrals derived in previous publications. We prove a generalization of the formula for single poles to multiple poles and we develop a strategy for dealing with higher-order pole integrals by reducing them to single pole integrals using Integration By Parts.
Generalization of the Lorenz-Haken model to atomic systems with different relaxation rates for the two laser levels
1995
Abstract The fundamental Lorenz-Haken laser model is generalized to the case of a two-level amplifying medium with different external relaxation rates for the two levels and with internal relaxation. This represents one further degree of freedom, and important quantitative differences in the laser dynamics. i.e., in the stationary solutions, linear stability analysis, and timedependent solutions, are found. No significant qualitative differences, however, are observed.