Search results for "SIP"
showing 10 items of 1280 documents
Time-optimal control of spin-1/2 particles with dissipative and generalized radiation-damping effects
2013
We analyze the time-optimal control of spin-1/2 particles with bounded field amplitudes in the presence of dissipative and radiation damping effects. Using tools of geometric optimal control theory, we determine different optimal syntheses for specific values of the system parameters. We show the nontrivial role of the effective radiation damping effect on the optimal control law.
Coherent vector pi-pulse in optical amplifiers
2007
We obtain an exact vector solitary solution for the amplification of an optical pulse with a time width short compared with both population and polarization decay time. This dissipative soliton results from the balance between the gain from inverted resonant two-level atoms and the linear loss of the host material. We suppose that the excited state of the active centers is degenerate on the projection of the angular moment. Numerical simulations demonstrate the stability of these vector dissipative solitons in the presence of both linear birefringence and group velocity dispersion of the host material.
Skyrmion Dynamics – from thermal diffusion to ultra-fast motion
2018
Summary form only given. Spintronics promises to be a paradigm shift from using the charge degree of freedom to using the spin degree of freedom. To this end three key requirements are: (i) stable spin structures for long term data retention; (ii) efficient spin manipulation for low power devices and (iii) ideally no susceptibility to stray fields as realized for antiferromagnets. We explore different materials classes to tackle these challenges and explore the science necessary for a disruptive new technology. To obtain ultimate stability, topological spin structures that emerge due to the Dzyaloshinskii-Moriya interaction (DMI), such as chiral domain walls and skyrmions are used. These po…
Coulomb excitation of re-accelerated 208Rn and 206Po beams
2013
In the present study, B( E2; 2(+)-> 0(+) ) values have been measured in the Rn-208 and Po-206 nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at CERN-ISOLDE. The resulting B(E2; 2(+)-> 0(+)) in 208Rn is similar to 0.08 e(2)b(2). These nuclei lie in, or at the boundary of the region where seniority scheme should persist. However, contributions from collective excitations may be present when moving away from the N = 126 shell closure. To date, surprisingly little is known of the transition probabilities between the low-spin states in this region.
Modeling a coronal loop heated by magnetohydrodynamic turbulence nanoflares
2005
We model the hydrodynamic evolution of the plasma confined in a coronal loop, 30,000 km long, subject to the heating of nanoflares due to intermittent magnetic dissipative events in the MHD turbulence produced by loop footpoint motions. We use the time-dependent distribution of energy dissipation along the loop obtained from a hybrid shell model, occurring for a magnetic field of about 10 G in the corona; the relevant heating per unit volume along the loop is used in the Palermo-Harvard loop plasma hydrodynamic model. We describe the results, focusing on the effects produced by the most intense heat pulses, which lead to loop temperatures between 1 and 1.5 MK.
On the effect of damping on dispersion curves in plates
2013
AbstractThis paper presents a study on quantitative prediction and understanding of time-harmonic wave characteristics in damped plates. Material dissipation is modelled by using complex-valued velocities of free dilatation and shear waves in an unbounded volume. As a numerical example, solution of the classical Rayleigh–Lamb problem for a viscoelastic plate is presented to illustrate and discuss the role of dissipation in the cut-off phenomenon and in the phenomenon of veering for dispersion curves. These phenomena are explained in more detail considering a simple model, which allows accurate asymptotic analysis of the perturbation of dispersion curves in the regions of cut-off and veering.
Spin-multipole nuclear matrix elements in thepnquasiparticle random-phase approximation: Implications forβandββhalf-lives
2017
Half-lives for 148 potentially measurable 2nd-, 3rd-, 4th-, 5th-, 6th-, and 7th-forbidden unique beta transitions are predicted. To achieve this, the ratio of the nuclear matrix elements (NMEs), calculated by the proton-neutron quasiparticle random-phase approximation (pnQRPA), ${M}_{\mathrm{pnQRPA}}$, and a two-quasiparticle (two-qp) model, ${M}_{\mathrm{qp}}$, is studied and compared with earlier calculations for the allowed Gamow-Teller (GT) ${1}^{+}$ and first-forbidden spin-dipole (SD) ${2}^{\ensuremath{-}}$ transitions. The present calculations are done using realistic single-particle model spaces and $G$-matrix based microscopic two-body interactions. In terms of the ratio $k={M}_{\m…
Flux expressions and NEMD perturbations for models of semi-flexible molecules
2001
We derive energy and momentum flux expressions, for systems composed of a general class of semi-flexible molecules, in the Ciccotti-Ferrario-Ryckaert linear constraint formalism. According to this formalism, the whole set of Cartesian coordinates is divided into basic (independent) and secondary (dependent) subsets. It is found that energy and momentum flux vectors have a simple and general expression using both basic and secondary coordinates. In the case of non-equilibrium molecular dynamics, we give general and simple heat and shear flow algorithms, deriving the dissipative fluxes in the space of all Cartesian coordinates. In comparison with previous derivations for some models of flexib…
Propagation of Dyakonon Wave-Packets at the Boundary of Metallodielectric Lattices
2013
We rigorously analyze the propagation of localized surface waves that takes place at the boundary between a semi-infinite layered metal-dielectric (MD) nanostructure cut normally to the layers and a isotropic medium. It is demonstrated that Dyakonov-like surface waves (also coined dyakonons) with hybrid polarization may propagate in a wide angular range. As a consequence, dyakonon-based wave-packets (DWPs) may feature sub-wavelength beamwidths. Due to the hyperbolic-dispersion regime in plasmonic crystals, supported DWPs are still in the canalization regime. The apparent quadratic beam spreading, however, is driven by dissipation effects in metal. This work was supported by the Spanish Mini…
Thermodynamic Approach to the Self-Diffusiophoresis of Colloidal Janus Particles
2019
Most available theoretical predictions for the self-diffusiophoretic motion of colloidal particles are based on the hydrodynamic thin boundary layer approximation in combination with a solvent body force due to a self-generated local solute gradient. This gradient is enforced through specifying boundary conditions, typically without accounting for the thermodynamic cost to maintain the gradient. Here, we present an alternative thermodynamic approach that exploits a direct link between dynamics and entropy production: the local detailed balance condition. We study two cases: First, we revisit self-propulsion in a demixing binary solvent. At variance with a slip velocity, we find that propuls…