Isospin singlet (pn) pairing and quartetting contribution to the binding energy of nuclei

Isospin singlet (pn) pairing as well as quartetting in nuclei is expected to arise near the symmetry line $N=Z$. Empirical values can be deduced from the nuclear binding energies applying special filters. Within the local density approximation, theoretical estimates for finite nuclei are obtained from results for the condensation energy of asymmetric nuclear matter. It is shown that the isospin singlet condensation energy drops down abruptly for |N-Z|~4 for medium nuclei in the region A=40. Furthermore, alpha-like quartetting and the influence of excitations are discussed.Comment: 19 pages, 19 figures, submitted to PR

Chaoticity and Dissipation of Nuclear Collective Motion in a Classical Model

We analyze the behavior of a gas of classical particles moving in a two-dimensional "nuclear" billiard whose multipole-deformed walls undergo periodic shape oscillations. We demonstrate that a single particle Hamiltonian containing coupling terms between the particles' motion and the collective coordinate induces a chaotic dynamics for any multipolarity, independently on the geometry of the billiard. The absence of coupling terms allows us to recover qualitatively the "wall formula" predictions. We also discuss the dissipative behavior of the wall motion and its relation with the order-to-chaos transition in the dynamics of the microscopic degrees of freedom.Comment: LateX, 11 pages, 7 figures available on request, to appear in the Proceedings of XXXIV Winter Meeting on Nuclear Physics, Bormio 22-27 January, 199

Pairing correlations of cold fermionic gases at overflow from a narrow to a wide harmonic trap

Within the context of Hartree-Fock-Bogoliubov theory, we study the behavior of superfluid Fermi systems when they pass from a small to a large container. Such systems can be now realized thanks to recent progress in experimental techniques. It will allow to better understand pairing properties at overflow and in general in rapidly varying external potentials

Fermion Condensation and Non Fermi Liquid Behavior in a Model with Long Range Forces

The phenomenon of the so called Fermion condensation, a phase transition analogous to Bose condensation but for Fermions, postulated in the past to occur in systems with strong momentum dependent forces, is reanalysed in a model with infinite range interactions. The strongly non Fermi Liquid behavior of this system is demonstrated analytically at $T=0$ and at $T\neq 0$ in the superconducting and normal phases. The validity of the quasiparticle picture is investigated and seems to hold true for temperatures less than the characteristic temperature $T_f$ of the Fermion condensation.Comment: 22 LaTeX pages, 6 figures can be obtained from [email protected]

BEC-BCS Crossover and the Liquid-Gas Phase Transition in Hot and Dense Nuclear Matter

The effect of nucleon-nucleon correlations in symmetric nuclear matter at finite temperature is studied beyond BCS theory. Starting from a Hartree-Fock description of nuclear matter with the Gogny effective interaction, we add correlations corresponding to the formation of preformed pairs and scattering states above the superfluid critical temperature within the in-medium T-matrix approach, which is analogous to the Nozieres-Schmitt-Rink theory. We calculate the critical temperature for a BEC superfluid of deuterons, of a BCS superfluid of nucleons, and in the crossover between these limits. The effect of the correlations on thermodynamic properties (equation of state, energy, entropy) and the liquid-gas phase transition is discussed. Our results show that nucleon-nucleon correlations beyond BCS play an important role for the properties of nuclear matter, especially in the low-density region.Comment: 11 pages, 12 figures; v2: minor modifications of the text, references adde

Academic Achievement Motivation in Hispanic Students

There is a lack of research on academic achievement motivation in Hispanic students, and instruments which measure achievement motivation have not been validated with Hispanic students. Fifteen regular-education teachers rated 67 third through fifth grade Hispanic students on the Teacher Rating of Academic Achievement Motivation (TRAAM). Students completed the Achievement Motivation Scale (AMS). Construct validity was investigated by examining the relationship of the TRAAM with the AMS. Criterion-related validity was established by examining the relationship of the TRAAM with Stanford Achievement Test (SAT) scores and grades. The TRAAM, AMS, Otis-Lennon School Ability Test (OLSAT) scores, and grades were used to predict academic achievement. Pearson product-moment correlations indicate that the TRAAM is a valid measure of academic achievement when used with Hispanic students. Stepwise multiple regression analysis revealed that the TRAAM was the best predictor of grades and it accounted for a significant portion of variance in standardized achievement scores

Academic Achievement Motivation in Hispanic Students

There is a lack of research on academic achievement motivation in Hispanic students, and instruments which measure achievement motivation have not been validated with Hispanic students. Fifteen regular-education teachers rated 67 third through fifth grade Hispanic students on the Teacher Rating of Academic Achievement Motivation (TRAAM). Students completed the Achievement Motivation Scale (AMS). Construct validity was investigated by examining the relationship of the TRAAM with the AMS. Criterion-related validity was established by examining the relationship of the TRAAM with Stanford Achievement Test (SAT) scores and grades. The TRAAM, AMS, Otis-Lennon School Ability Test (OLSAT) scores, and grades were used to predict academic achievement. Pearson product-moment correlations indicate that the TRAAM is a valid measure of academic achievement when used with Hispanic students. Stepwise multiple regression analysis revealed that the TRAAM was the best predictor of grades and it accounted for a significant portion of variance in standardized achievement scores

Modeling Launch Vehicle Success Using Artificial Neural Networks

Expendable launch vehicles in the United States currently have a reliability of 92%. The failures that do occur cost millions of dollars in spacecraft replacement, lost revenue, and other expenses. These costs are passed on in higher insurance rates and launch vehicle price. If the launch outcome of the launch vehicles could be better predicted, the overall cost of launching payloads into space would decrease. This study used artificial neural networks to model the overall launch outcome of a launch vehicle so that the results of a launch could be predicted. Two neural network architectures--MLP and fuzzy ARTMAP--were trained on historical launch data of Atlas, Delta, and Titan launch vehicles. The networks were then tested on their ability to generalize to new data. Fuzzy ARTMAP performed slightly better than MLP overall, but neither network can be used during launch countdown today. Future application of the networks in real-time during the vehicle launch countdown will require the use of more launch specific data

Alpha-particle condensation in nuclei

A round up of the present status of the conjecture that n alpha nuclei form an alpha-particle condensate in excited states close to the n alpha threshold is given. Experiments which could demonstrate the condensate character are proposed. Possible lines of further theoretical developments are discussed.Comment: 6 page

Cooper pair sizes in superfluid nuclei in a simplified model

Cooper pair sizes are evaluated in a simple harmonic oscillator model reproducing the values of sophisticated HFB calculations. Underlying reasons for the very small sizes of 2.0-2.5 fm of Cooper pairs in the surface of nuclei are analysed. It is shown that the confining properties of the nuclear volume is the dominating effect. It is argued that for Cooper pair sizes LDA is particularly inadapted.Comment: 8 pages, 6 figure