Luther-Emery Phase and Atomic-Density Waves in a Trapped Fermion Gas

The Luther-Emery liquid is a state of matter that is predicted to occur in one-dimensional systems of interacting fermions and is characterized by a gapless charge spectrum and a gapped spin spectrum. In this Letter we discuss a realization of the Luther-Emery phase in a trapped cold-atom gas. We study by means of the density-matrix renormalization-group technique a two-component atomic Fermi gas with attractive interactions subject to parabolic trapping inside an optical lattice. We demonstrate how this system exhibits compound phases characterized by the coexistence of spin pairing and atomic-density waves. A smooth crossover occurs with increasing magnitude of the atom-atom attraction to a state in which tightly bound spin-singlet dimers occupy the center of the trap. The existence of atomic-density waves could be detected in the elastic contribution to the light-scattering diffraction pattern.Comment: 10 pages, 3 figures, 1 Table, submitted to Phys. Rev. on July 25th 200

Diffraction in time of a confined particle and its Bohmian paths

Diffraction in time of a particle confined in a box which its walls are removed suddenly at $t=0$ is studied. The solution of the time-dependent Schr\"{o}dinger equation is discussed analytically and numerically for various initial wavefunctions. In each case Bohmian trajectories of the particles are computed and also the mean arrival time at a given location is studied as a function of the initial state.Comment: 8 pages, 6 figure

Disclosing hidden information in the quantum Zeno effect: Pulsed measurement of the quantum time of arrival

Repeated measurements of a quantum particle to check its presence in a region of space was proposed long ago [G. R. Allcock, Ann. Phys. {\bf 53}, 286 (1969)] as a natural way to determine the distribution of times of arrival at the orthogonal subspace, but the method was discarded because of the quantum Zeno effect: in the limit of very frequent measurements the wave function is reflected and remains in the original subspace. We show that by normalizing the small bits of arriving (removed) norm, an ideal time distribution emerges in correspondence with a classical local-kinetic-energy distribution.Comment: 5 pages, 4 figures, minor change

Companion modelling for exploring natural resource management strategies in Palawanm, The Philippines

This paper reports experiences and lessons of a continuing study on the use of a contemporary analytical tool, Multi-agent Systems (MAS), to study the dynamics and complex interactions among stakeholders in the management of common renewable resources. In the MAS model, a renewable resource management system is represented with different autonomous entities, called agents, that are able to act, interact with other agents, and be affected by objects in the environment. In this study, the MAS model is developed using the Companion Modelling (ComMod) approach, a collaborative development of a MAS model between the stakeholders and researchers which places primary importance on the quality of process to ensure that the tools developed are acceptable and used with confidence. This approach involves the development and application of computer simulations and role-playing games (RPGs) to validate the MAS model as well as learn from it. Inferences are drawn from the learning and negotiation processes that the stakeholders and researchers undergo in the collaborative development of the MAS model and the techniques used to realize this model, i.e. computer simulation and RPG, as well as the development of a unified resource management plan for three villages. For the community, having acknowledged the RPG as a reliable representation of their reality, they see these tools as vehicles to reach the appropriate stakeholders and communicate their concerns about their livelihoods and resources. For local government agencies and non-government organizations, these tools serve as eye-openers about the dire livelihood conditions of the community. Furthermore, local governments see the RPG and computer simulation as effective techniques to inform and educate people about their plans or programs for the management of resources and livelihood for the community. The stakeholders also agree that these tools are useful in coming together and discussing issues pertaining to the management of their natural resources and livelihood activities. Given the benefits that could be derived from ComMod and MAS modelling in NRM, these techniques display a great potential in plantation management for increasing the financial returns