An attractive nucleon-nucleon spin-orbit force from skyrmions with dilatons

Within the skyrmion approach for the nucleon-nucleon force, difficulties have been experienced in obtaining an isoscalar attractive spin-orbit potential, in parallel to the problems of finding attraction in the isoscalar central potential. We here study the spin-orbit force using a skyrmion with four- and six-derivative stabilizing terms in the lagrangian as well as with the crucial addition of a dilaton. With these features present the spin-orbit force proves to be attractive as does the central potential. In the absence of the dilaton, attraction can also be found for the spin-orbit potential but only at the expense of a greatly over-emphasized term with six derivatives and a continuing absence of attraction in the central potential.Comment: 8 pages plus 5 figures in uuencoded tar-compressed for

Changes in the radius of a nucleon in interaction with another nucleon

We consider a two-nucleon system described by two different skyrmion models that provide attraction for the central NN potential. One of these models is based on the product ansatz and the other on dilaton coupling. Within these models we ask the question, To what degree does the nucleon swell or shrink when the internucleon separation distance is appropriate to attraction or repulsion? We find typically swelling of 3 to 4 percent for central attraction of some 40 to 50 MeV.Comment: Nine pages of plain TeX plus two uuencoded figure

The breakdown of the Nagaoka phase in the 2D t-J model

In the limit of weak exchange, J, at low hole concentration, the ground state of the 2D t-J model is believed to be ferromagnetic. We study the leading instability of this Nagaoka state, which emerges with increasing J. Both exact diagonalization of small clusters, and a semiclassical analytical calculation of larger systems show that above a certain critical value of the exchange, Nagaoka's state is unstable to phase separation. In a finite-size system a bubble of antiferromagnetic Mott insulator appears in the ground state above this threshold. The size of this bubble depends on the hole concentration and scales as a power of the system size, N

Hot nuclear matter with dilatons

We study hot nuclear matter in a model based on nucleon interactions deriving from the exchange of scalar and vector mesons. The main new feature of our work is the treatment of the scale breaking of quantum chromodynamics through the introduction of a dilaton field. Although the dilaton effects are quite small quantitatively, they affect the high-temperature phase transition appreciably. We find that inclusion of the dilaton leads to a metastable high-density state at zero pressure, similar to that found by Glendenning who considered instead the admixture of higher baryon resonances.Comment: 10 pages, LaTeX with equation.sty (optional) and epsfig.sty, 11 figures packed with uufiles. Final, published version (small changes from original preprint

Higher-level goals in the processing of human action events

The concept of a goal critically separates dynamic events involving humans from other events. Human behaviours are motivated by goals, which are known to the actor but typically inferred on the part of the observer. Goals can be hierarchical in nature, such that a collection of sub-goals (e.g., getting a mug, boiling water) can be nested under a higher-level goal (e.g., making tea), which can be further nested under an even higher-level goal (e.g., making breakfast). The diverse set of talks in this symposia all highlight the foundational role that goals play in action processing and representation. Eisenberg et al. detail how online prediction of others’ goals shapes observers’ sampling of information during action observation. Howard and Woodward provide evidence that children’s memory for non-human events can be facilitated by priming children with their own goal-directed actions. Loucks and Meltzoff highlight the importance of goal structure in children’s memory for complex action sequences. Finally, Cooper presents a computational model to explain the emergence of goal-directed action hierarchies

Proton spin content from skyrmions

It is well known that in lowest order the skyrmion model of the nucleon gives vanishing spin content. With new data indicating a proton spin content $\Delta\Sigma = 0.22\pm 0.14,$ it is an increasing challenge to find ways in which the skyrmion can move away from the null result. We show here that a particular term in the skyrmion lagrangian in SU(3) involving six derivatives of the field can, with plausible parameters, yield a spin content consistent with present experiment.Comment: 8 page

Pathological Behavior in the Spectral Statistics of the Asymmetric Rotor Model

The aim of this work is to study the spectral statistics of the asymmetric rotor model (triaxial rigid rotator). The asymmetric top is classically integrable and, according to the Berry-Tabor theory, its spectral statistics should be Poissonian. Surprisingly, our numerical results show that the nearest neighbor spacing distribution $P(s)$ and the spectral rigidity $\Delta_3(L)$ do not follow Poisson statistics. In particular, $P(s)$ shows a sharp peak at $s=1$ while $\Delta_3(L)$ for small values of $L$ follows the Poissonian predictions and asymptotically it shows large fluctuations around its mean value. Finally, we analyze the information entropy, which shows a dissolution of quantum numbers by breaking the axial symmetry of the rigid rotator.Comment: 11 pages, 7 figures, to be published in Phys. Rev.

Meaningful engagement: computer-based interactive media art in public space.

Interactive technologies, including electronic devices are increasingly being utilized as a medium for artistic expression and have been placed in freely accessible public environments with mixed results. When audiences encounter computer-based interactive media arts in a public space they are drawn by various interactivities, to play and experiment with them. However, whether the audience is able to gain a meaningful experience through those physical interactivities has remained an issue of both theoretical and practical debate. This paper will focus on these aspects, most specifically through the study of interactive art in freely accessible public space. The author proposes four new conceptual/analytical tools for examining the subject. It is anticipated that this paper will provide possible alternative strategies for both artists and art researchers in this field with a purpose to enhance intellectual engagement with their audiences, so as to succeed in leading interactors to obtain meaningful experience and rewards