Di-nucleus dynamics towards fusion of heavy nuclei

This work has been first presented at : First Workshop on State of the Art in Nuclear Cluster Physics, 13/16-05-2008 Strasbourg (France)International audienceThe Two-Step Model for fusion of massive systems is briefly recapitulated, which clar- ifies the mechanism of so-called fusion hindrance. Since the neck changes the potential landscape, especially the height of the conditional saddle point, time evolution of the neck degree of freedom plays a crucial role in fusion. We analytically solve time-evolution of nuclear shape of the composite system from di-nucleus to mono-nucleus. The time- dependent distribution function of the neck is obtained, which elucidates dynamics of fusion processes in general, and thus, is useful for theoretical predictions on synthesis of the superheavy elements with various combinations of incident heavy ions

Fusion hindrance of heavy ions: role of the neck

International audienceFusion of heavy ions is largely hindered because of the appearance of an inner barrier between the contact point of the two colliding nuclei and the compound nucleus. But there are still quantitative ambiguities on the size of the barrier and on the role of the dissipation. In this paper we stress the importance of the neck of the composite system on the hindrance of the fusion of heavy nuclei. We show that the \denecking" process is very quick compared to the other collective degrees of freedom as the relative distance. This behavior of the neck will change the potential seen by the relative distance on the way to fusion and its e ective initial value through a dynamical coupling. Both e ects contribute to the hindrance of fusion

Dynamics of massive systems and synthesis of superheavy elements

International audienceFor the synthesis of superheavy elements, it is indisensable to divide process into two steps : overcoming the Coulomb barrier and passing over the conditional saddle or the ridgeline. To facilitate the understanding of the mechanism which explains the fusion hindrance, we first emply an analytic model with an inverted parabola for the saddle. Then, results by realistic calculations are given for the cold fusion. Ambiguities of the model are also discussed for future investigations. Since the model is general, it is applied to incident channels with neutron-rich projectile and/or targets. These are necessary for synthesis of nuclides on so-called superheavy island around Z=114 and N=18

Magnetic properties and switching volumes of nanocrystalline SmFeSiC films

Systematic studies of the effects of Si addition on the magnetic and magnetization reversal properties of SmFeSiC films are presented. The magnetic switching volume and other magnetic parameters (e.g., coercivity) are strongly dependent upon the Si content. Correlations between switching volume, coercivity, and the intergrain interactions are discussed

Parton energy loss in glasma

We study the synchrotron-like gluon emission in $AA$-collisions from fast partons due to interaction with the coherent glasma color fields. Our results show that for RHIC and LHC conditions the contribution of this mechanism to parton energy loss is much smaller than the radiative energy loss in the plasma phase.Comment: 14 pages, 3 figure

Application of Onset Theory to Onset of Transverse Cracking in Fabric Composites

A paper presented at ICCM-19 included a methodology for application of Onset Theory to the prediction of microcracking in the transverse plies of orthogonal [0/90] fabric laminates. This paper applies the methodology to predict damage locations and laminate strains for failure of plain weave fabric specimens manufactured from two material systems – HTS40/RTM6 and T300/CYCOM970. The laminate strains are first dehomogenised to define local strains in the tow architecture of the fabric. This is achieved using meso-mechanical unit cell analysis in which the resin and tows are modelled as continua. For a selection of predefined critical locations in the tow bundles, the strains are further dehomogenised using an identical procedure as the one defined for the uni-directional specimens in the previous applications. The influence of matrix plasticity and temperature dependent mechanical and thermal properties of the RTM6 resin are applied in the dehomogenisation procedure. The Onset theory predictions for damage locations were compared to those obtained from microscopic surveys of partially failed plain weave fabric specimens

Variation of Bar Strength with Central Velocity Dispersion in Spiral Galaxies

We investigate the variation of bar strength with central velocity dispersion in a sample of barred spiral galaxies. The bar strength is characterized by $Q_g$, the maximal tangential perturbation associated with the bar, normalized by the mean axisymmetric force. It is derived from the galaxy potentials which are obtained using near-infrared images of the galaxies. However, $Q_g$ is sensitive to bulge mass. Hence we also estimated bar strengths from the relative Fourier intensity amplitude ($A_{2}$) of bars in near-infrared images. The central velocity dispersions were obtained from integral field spectroscopy observations of the velocity fields in the centers of these galaxies; it was normalized by the rotation curve amplitude obtained from HI line width for each galaxy. We found a correlation between bar strengths (both $Q_g$ and $A_{2}$) and the normalized central velocity dispersions in our sample. This suggests that bars weaken as their central components become kinematically hotter. This may have important implications for the secular evolution of barred galaxies.Comment: To appear in Ap&S

Influence of a classical homogeneous gravitational field on dissipative dynamics of the Jaynes-Cummings model with phase damping

In this paper, we study the dissipative dynamics of the Jaynes-Cummings model with phase damping in the presence of a classical homogeneous gravitational field. The model consists of a moving two-level atom simultaneously exposed to the gravitational field and a single-mode traveling radiation field in the presence of the phase damping. We present a quantum treatment of the internal and external dynamics of the atom based on an alternative su(2) dynamical algebraic structure. By making use of the super-operator technique, we obtain the solution of the master equation for the density operator of the quantum system, under the Markovian approximation. Assuming that initially the radiation field is prepared in a Glauber coherent state and the two-level atom is in the excited state, we investigate the influence of gravity on the temporal evolution of collapses and revivals of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and quadrature squeezing of the radiation field in the presence of phase damping.Comment: 25 pages, 15 figure