Microscopic calculations of double and triple Giant Resonance excitation in heavy ion collisions

We perform microscopic calculations of the inelastic cross sections for the double and triple excitation of giant resonances induced by heavy ion probes within a semicalssical coupled channels formalism. The channels are defined as eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective RPA phonons. Therefore, they are superpositions of several multiphonon states, also with different numbers of phonons and the spectrum is anharmonic. The inclusion of (n+1) phonon configurations affects the states whose main component is a n-phonon one and leads to an appreacible lowering of their energies. We check the effects of such further anharmonicities on the previous published results for the cross section for the double excitation of Giant Resonances. We find that the only effect is a shift of the peaks towards lower energies, the double GR cross section being not modified by the explicity inclusion of the three-phonon channels in the dynamical calculations. The latters give an important contribution to the cross section in the triple GR energy region which however is still smaller than the experimental available data. The inclusion of four phonon configurations in the structure calculations does not modify the results.Comment: Revtex4, to be published in PR

Probing the Structure of Halo Nuclei

Our understanding of halo nuclei has so far relied on high-energy scattering and reactions, but a number of uncertainties remain. I discuss in general terms the new range of observables which will be measured by experiments around the Coulomb barrier, and how some details of the reaction mechanisms still need to be clarified.Comment: Proceedings of FUSION97 conference (March 1997), South Durras, Australia. Submitted to J. Physics G: special issue `Heavy ion collisions at near barrier energies'. No figures; uses IOPConf.sty (included

Asymptotically (anti) de Sitter Black Holes and Wormholes with a Self Interacting Scalar Field in Four Dimensions

The aim of this paper is to report on the existence of a wide variety of exact solutions, ranging from black holes to wormholes, when a conformally coupled scalar field with a self interacting potential containing a linear, a cubic and a quartic self interaction is taken as a source of the energy-momentum tensor, in the Einstein theory with a cosmological constant. Among all the solutions there are two particularly interesting. On the one hand, the spherically symmetric black holes when the cosmological constant is positive; they are shown to be everywhere regular, namely there is no singularity neither inside nor outside the event horizon. On the other hand, there are spherically symmetric and topological wormholes that connect two asymptotically (anti) de Sitter regions with a different value for the cosmological constant. The regular black holes and the wormholes are supported by everywhere regular scalar field configurations.Comment: Final versio

¿Qué es una carretera inteligente?

A smart road is the planning of avenues or roads that become advanced intelligent platforms, which allow detailed infrastructure to embody or develop their functions (such as traffic signals and tolls). It allows vehicles to communicate and share an essential information base with deterministic characteristics between a system for receiving and exporting information. In this way, a driver can know in advance if a traffic accident has occurred or if weather conditions are making it difficult for vehicles to pass. This article documents several characteristic aspects of the functioning of each of the parts that make up the intelligent highway.Una carretera inteligente consiste en la planeación de avenidas o caminos que se conviertan en avanzadas plataformas inteligentes, que permiten que la detallada infraestructura plasme o desarrolle sus funciones (como señales de tránsito y peajes). Permite que los vehículos se comuniquen y compartan una base información esencial con características determinantes a los factores, entre un sistema de recepción y exportación de información. De esta manera, un conductor puede conocer con anticipación si se registró un accidente de tránsito o si las condiciones climáticas están dificultando el paso de vehículos. Este articulo documenta varios aspectos característicos del funcionamiento de cada una de las partes que componen a la carretera inteligentes

Energization of charged test particles in magnetohydrodynamic fields: waves vs turbulence picture

Direct numerical simulations of 3D compressible MHD turbulence were performed in order to study the relation between waves modes and coherent structures and the consequent energization of test particles. Moreover, the question of which is the main mechanism of this particle energization is rigorously discussed. In particular, using the same initial conditions, we analyzed the non-linear and linear evolution of a turbulent state along with the case of randomized phases. Then, the behavior of the linear and non-linear simulations were compared through the study of time evolution of particle kinetic energy and preferential concentration. Also, spatio temporal spectra were used to identify the presence of wave modes and quantify the fraction of energy around the MHD modes in linear and non-linear simulations. Finally, the variation of the correlation time of the external forcing is studied in detail along with the effect on the particle energization (and clustering) and the presence of wave modes. More specifically, particle energization tends to decrease when the fraction of linear energy increase, supporting the idea that energization by structures is the dominant mechanism for particle energization instead of resonating with wave modes as suggested by Fermi energization theory

Ga+, In+ and Tl+ Impurities in Alkali Halide Crystals: Distortion Trends

A computational study of the doping of alkali halide crystals (AX: A = Na, K; X = Cl, Br) by ns2 cations (Ga+, In+ and Tl+) is presented. Active clusters of increasing size (from 33 to 177 ions) are considered in order to deal with the large scale distortions induced by the substitutional impurities. Those clusters are embedded in accurate quantum environments representing the surrounding crystalline lattice. The convergence of the distortion results with the size of the active cluster is analyced for some selected impurity systems. The most important conclusion from this study is that distortions along the (100) and (110) crystallographic directions are not independent. Once a reliable cluster model is found, distortion trends as a function of impurity, alkali cation and halide anion are identified and discussed. These trends may be useful when analycing other cation impurities in similar host lattices.Comment: LaTeX file. 7 pages and 2 pictures. Accepted for publication in J. Chem. Phy

Maximizing the Conditional Expected Reward for Reaching the Goal

The paper addresses the problem of computing maximal conditional expected accumulated rewards until reaching a target state (briefly called maximal conditional expectations) in finite-state Markov decision processes where the condition is given as a reachability constraint. Conditional expectations of this type can, e.g., stand for the maximal expected termination time of probabilistic programs with non-determinism, under the condition that the program eventually terminates, or for the worst-case expected penalty to be paid, assuming that at least three deadlines are missed. The main results of the paper are (i) a polynomial-time algorithm to check the finiteness of maximal conditional expectations, (ii) PSPACE-completeness for the threshold problem in acyclic Markov decision processes where the task is to check whether the maximal conditional expectation exceeds a given threshold, (iii) a pseudo-polynomial-time algorithm for the threshold problem in the general (cyclic) case, and (iv) an exponential-time algorithm for computing the maximal conditional expectation and an optimal scheduler.Comment: 103 pages, extended version with appendices of a paper accepted at TACAS 201