Search results for "classical"
showing 10 items of 2294 documents
Translationally invariant coupled cluster method in coordinate space for nuclei
2002
We study a formulation of the translationally invariant coupled cluster method in coordinate space for finite nuclei. The new formulation remedies convergence problems that plagued previous calculations in configuration space. The method is applied to light nuclei using semi-realistic central interactions.
Calculated Line Broadening Coefficients in the nu2 Band of CH3D Perturbed by Helium
2003
International audience; Line broadening coefficients have been calculated, at room temperature, for lines in the P and R branches of the nu2 band of monodeuterated methane. A properly symmetrized semiclassical model with parabolic relative trajectories has been used. Two interaction potential models have been considered. The first is a Lennard-Jones type atom-atom potential, while the second one was derived from ab initio calculations. The calculated line widths were compared to the available experimental data and a satisfactory agreement was found, although the model contains no other adjustable parameters than the four atomic Lennard-Jones ones. Nonetheless, failures of calculations have …
Attenuation of the fourth sound in liquid helium II via extended thermodynamics
2004
Abstract This work continues a study begun in previous works, where a non-standard model of liquid helium II is proposed, in which a small entropy transfer is associated with the superfluid component. In this work the influence of this superfluid entropy on the propagation of the fourth sound is analyzed. From experimental data for velocities and attenuations of the first and second sound, the model provides speed and attenuation coefficient of the fourth sound in a porous medium as a function of the ratio ss/s between the superfluid entropy ss and the total entropy s. These values are determined in the two limiting cases ss/s=0 and =0.02, for various values of temperature and pressure.
London equation of state for a quantum-hard-sphere system
1994
The London analytical interpolation equation between zero and packing densities for the ground-state energy of a many-boson hard-sphere system is corrected for the reduced mass of a pair of particles in a ``sphere-of-influence'' picture. It is thus brought into good agreement with computer simulations and with experimental results extrapolated out to close packing.
Hydrodynamical and Emission Simulations of Relativistic Jets: Stability and Generation of Superluminal and Stationary Components
2001
We present 2D hydrodynamical and emission simulations of the jet stabilityafter the introduction of strong perturbations on a relativistic jet. These simulations show that the interaction of a single strong perturbation with the underlying jet results in the formation of multiple conical shocks with very specific observational properties.
Electron Induced Massive Dynamics of Magnetic Domain Walls
2019
We study the dynamics of domain walls (DWs) in a metallic, ferromagnetic nanowire. We develop a Keldysh collective coordinate technique to describe the effect of conduction electrons on rigid magnetic structures. The effective Lagrangian and Langevin equations of motion for a DW are derived. The DW dynamics is described by two collective degrees of freedom: position and tilt-angle. The coupled Langevin equations therefore involve two correlated noise sources, leading to a generalized fluctuation-dissipation theorem (FDT). The DW response kernel due to electrons contains two parts: one related to dissipation via FDT, and another `inertial' part. We prove that the latter term leads to a mass …
Shears Mechanism in theA∼110Region
1999
Lifetimes of states in a rotational-like $M1$ band in ${}^{110}\mathrm{Cd}$ have been determined through a Doppler-shift attenuation method measurement performed with the Gammasphere array. The deduced $B(M1)$ values, which agree well with the predictions of the tilted axis cranking model, clearly confirm that it has the character of a shears band. Using a semiclassical scheme of the coupling of two long $j$ vectors we deduce information on the strength and form of the effective interaction between the constituent nucleons. These results are the first definitive evidence of the shears mechanism and ``magnetic rotation'' in this mass region.
Dynamics of a flexible magnetic chain in a rotating magnetic field.
2004
The model of an elastic magnetic rod is applied for a study of a behavior of the flexible magnetic particle chain in a rotating magnetic field. By numerical simulation it is shown that behavior of a flexible magnetic chain is characterized by the existence of a critical frequency beyond which the dynamics of the rod is periodic with subsequent stages of bending and straightening. The value of the critical frequency found is explained by a simple model. Below the critical frequency the chain is bent and rotates synchronously with a field. It is illustrated that in particular cases the considered model reproduces phenomena observed experimentally and numerically for the magnetic particle chai…
Longitudinal and Transverse Correlation Functions in the 4 Model below and near the Critical Point
2010
We have extended our method of grouping Feynman diagrams (GFD theory) to study the transverse and longitudinal correlation functions G⊥(k) and G‖(k) in φ model below the critical point (T < Tc) in the presence of an infinitesimal external field. Our method allows a qualitative analysis without cutting the perturbation series. The long-wave limit k → 0 has been studied at T < Tc, showing that G⊥(k) a k−λ⊥ and G‖(k) b k−λ‖ with exponents d/2 < λ⊥ < 2 and λ‖ = 2λ⊥−d are the physical solutions of our equations at the spatial dimensionality 2 < d < 4, which coincides with the asymptotic solution at T → Tc as well as with a nonperturbative renormalization group (RG) analysis provided in our paper…
Mechanical energy states during running.
1978
Changes in total mechanical work and its partitioning into different energy states (kinetic, potential and rotational) during a step cycle of running were investigated on six well trained athletes who ran at the test speeds of 40, 60, 80, and 100% (9.3 +/- 0.3 m/s) of maximum. Cinematographic techniques were utilized to calculate the mechanical energy states as described by Norman et al. (1976), using a 13 segment mechanical model of a runner as the basis for the computations. The data showed that both the kinetic and rotational energy increased parabolically but the potential energy decreased linearly with increases in running velocity. The calculated power of the positive work phase incre…