Search results for "Model theory"
showing 10 items of 681 documents
On the Age, Spectral Type, Orbit, and Comparison to Evolutionary Models of AB Dor C
2005
Structural, electronic, and magnetic properties of tetragonalMn3−xGa: Experiments and first-principles calculations
2008
This work reports on the electronic, magnetic, and structural properties of the binary intermetallic compounds ${\mathrm{Mn}}_{3\ensuremath{-}x}\mathrm{Ga}$. The tetragonal ${\mathrm{DO}}_{22}$ phase of the ${\mathrm{Mn}}_{3\ensuremath{-}x}\mathrm{Ga}$ series, with $x$ varying from 0 to 1.0 in steps of $x=0.1$, was successfully synthesized and investigated. It was found that all these materials are hard magnetic, with energy products ranging from $10.1\phantom{\rule{0.3em}{0ex}}\mathrm{kJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}3}$ for low Mn content $(x\ensuremath{\rightarrow}1)$ to $61.6\phantom{\rule{0.3em}{0ex}}\mathrm{kJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensurema…
Coupled-cluster Theory
2002
Interpretation of KPFM Data with the Weight Function for Charges
2018
The KPFM signal for systems containing local charges can be expressed as a weighted sum over all local charges. The weight function for charges quantifies the contribution of each charge, depending on its position. In this chapter, we evaluate the KPFM weight function for charges by analyzing several application-relevant model systems. The intention of this chapter is to provide insights into the KPFM contrast formation in order to facilitate the KPFM data interpretation. For this, we concentrate on three model systems: (A) a conductive sample in ultra-high vacuum, (B) a dielectric sample in ultra-high vacuum, and (C) a dielectric sample in water. We calculate the weight function for charge…
Covariant determination of the Weyl tensor geometry
2001
We give a covariant and deductive algorithm to determine, for every Petrov type, the geometric elements associated with the Weyl tensor: principal and other characteristic 2-forms, Debever null directions and canonical frames. We show the usefulness of these results by applying them in giving the explicit characterization of two families of metrics: static type I spacetimes and type III metrics with a hypersurface-orthogonal Killing vector. PACS numbers: 0240M, 0420C
On the invariant symmetries of the D-metrics
2007
We analyze the symmetries and other invariant qualities of the $\mathcal{D}$-metrics (type D aligned Einstein Maxwell solutions with cosmological constant whose Debever null principal directions determine shear-free geodesic null congruences). We recover some properties and deduce new ones about their isometry group and about their quadratic first integrals of the geodesic equation, and we analyze when these invariant symmetries characterize the family of metrics. We show that the subfamily of the Kerr-NUT solutions are those admitting a Papapetrou field aligned with the Weyl tensor.
Dissipative solitons and their interactions
2007
Coupled soliton pairs in nonlinear dissipative systems can exist in various forms. They can be stationary, or they can pulsate periodically, quasi-periodically or chaotically, as is the case for single solitons. Each type is stable in the sense that a given bound state exists in the same form inde.nitely. Single solitons can be perfectly stable for a given set of parameters. However, this does not mean that a bound state formed from them is either stationary or stable. Moreover, their relations can be highly complicated. Such is the life of dissipative solitons. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Soliton complexes in dissipative systems: Vibrating, shaking and mixed soliton pairs
2007
We show, numerically, that coupled soliton pairs in nonlinear dissipative systems modeled by the cubic-quintic complex Ginzburg-Landau equation can exist in various forms. They can be stationary, or they can pulsate periodically, quasiperiodically, or chaotically, as is the case for single solitons. In particular, we have found various types of vibrating and shaking soliton pairs. Each type is stable in the sense that a given bound state exists in the same form indefinitely. New solutions appear at special values of the equation parameters, thus bifurcating from stationary pairs. We also report the finding of mixed soliton pairs, formed by two different types of single solitons. We present …
Impact of a temporal sinusoidal phase modulation on the optical spectrum
2018
International audience; We discuss the effects of imparting a temporal sinusoidal phase modulation to a continuous wave on the frequency spectrum. While a practical analytical solution to this problem already exists, we present here a physical interpretation based on interference processes. This simple model will help the students better understand the origin of the oscillatory structure that can be observed in the resulting spectrum and that is characteristic of Bessel functions of the first kind. We illustrate our approach with an example from the field of optics.
Light bullets and dynamic pattern formation in nonlinear dissipative systems
2005
In the search for suitable new media for the propagation of (3+1) D optical light bullets, we show that nonlinear dissipation provides interesting possibilities. Using the complex cubic-quintic Ginzburg-Landau equation model with localized initial conditions, we are able to observe stable light bullet propagation or higher-order transverse pattern formation. The type of evolution depends on the model parameters. ©2005 Optical Society of America.