arXiv subjects
Publications and source records attributed to C. Y. Wong.
The excitation function for the 7 alpha de-excitation of $^{28}$Si nuclei excited to high excitation energies in the collisions of 35 MeV/nucleon $^{28}$Si with $^{12}$C reveals resonance structures that may indicate the population of high spin toroidal isomers such as those predicted by a number of recent theoretical calculations. This interpretation is supported by extended theoretical analyses.
The dynamical origin of opinion polarization in the real world is an interesting topic physical scientists may help to understand. To properly model the dynamics, the theory must be fully compatible with findings by social psychologists on microscopic opinion change. Here we introduce a generic model of opinion formation with homogeneous agents based on the well-known social judgment theory in social psychology by extending a similar model proposed by Jager and Amblard. The agents' opinions will eventually cluster around extreme and/or moderate opinions forming three phases in a two-dimensional parameter space that describes the microscopic opinion response of the agents. The dynamics of this model can be qualitatively understood by mean-field analysis. More importantly, first-order phase transition in opinion distribution is observed by evolving the system under a slow change in the system parameters, showing that punctuated equilibria in public opinion can occur even in a fully connected social network.
Co(x nm, x=10nm or 40nm)/Cu(5nm)/Co(2.5nm) layers were deposited between copper electrodes in SiO2 vias. Magnetic states, and the corresponding resistance states, of these devices were switched by electric currents perpendicular to the layers. The I-V loops show asymmetric behavior with hysteresis. When electrons flow in the direction from thick to thin Co layer (positive current), multiple switches were observed on increasing current up to a chosen maximum positive I(write). On decreasing current from I(write), the I-V curve was smooth and characterized by considerably lower resistance. Under reverse current, an abrupt switch to the high resistance state occurred at the current value I(erase)~ -0.9*I(write). Resistance had a maximum at zero current in both states, where the ratio R(high)/R(low) could be as high as factor of four.
In this contribution we summarize experimental information and theoretical results for the dissociation cross sections of charmonium by light hadrons. Theoretical predictions for these RHIC-related processes differ by orders of magnitude over the physically relevant energy range. The results found by the author and collaborators using a constituent interchange model, which predicts cross sections in the mb region near threshold, are discussed in more detail.
We study the Anderson localization in a weakly coupled multilayer system with a strong magnetic field perpendicular to the layers. The phase diagram of 1/3 flux quanta per plaquette is obtained. The phase diagram shows that a three-dimensional quantum Hall effect phase exists for a weak on-site disorder. For intermediate disorder, the system has insulating and normal metallic phases separated by a mobility edge. At an even larger disorder, all states are localized and the system is an insulator. The critical exponent of the localization length is found to be $ν=1.57\pm0.10$.