Time variation of the fine structure constant in decrumpling or TVSD model

Within the framework of a model universe with time variable space dimension (TVSD), known as decrumpling or TVSD model, we study the time variation of the fine structure constant. Using observational bounds on the present time variation of the fine structure constant, we are able to obtain the present time variation of spatial dimensions.Comment: 10 pages, accepted for publication in Int.J.Mod.Phys.

Some Remarks about Variable Mass Systems

We comment about the general argument given to obtain the rocket equation as it is exposed in standard textbooks. In our opinion, it can induce students to a wrong answer when solving variable mass problems.Comment: 2 page

Sommerfeld's image method in the calculation of van der Waals forces

We show how the image method can be used together with a recent method developed by C. Eberlein and R. Zietal to obtain the dispersive van der Waals interaction between an atom and a perfectly conducting surface of arbitrary shape. We discuss in detail the case of an atom and a semi- infinite conducting plane. In order to employ the above procedure to this problem it is necessary to use the ingenious image method introduced by Sommerfeld more than one century ago, which is a generalization of the standard procedure. Finally, we briefly discuss other interesting situations that can also be treated by the joint use of Sommerfeld's image technique and Eberlein-Zietal method.Comment: To appear in the proceedings of Conference on Quantum Field Theory under the Influence of External Conditions (QFEXT11

Matter Wave Scattering and Guiding by Atomic Arrays

We investigate the possibility that linear arrays of atoms can guide matter waves, much as fiber optics guide light. We model the atomic line as a quasi-1D array of s wave point scatterers embedded in 2D. Our theoretical study reveals how matter wave guiding arises from the interplay of scattering phenomena with bands and conduction along the array. We discuss the conditions under which a straight or curved array of atoms can guide a beam focused at one end of the array.Comment: Submitted to Phys. Rev.

Approximate Analytic Solution for the Spatiotemporal Evolution of Wave Packets undergoing Arbitrary Dispersion

We apply expansion methods to obtain an approximate expression in terms of elementary functions for the space and time dependence of wave packets in a dispersive medium. The specific application to pulses in a cold plasma is considered in detail, and the explicit analytic formula that results is provided. When certain general initial conditions are satisfied, these expressions describe the packet evolution quite well. We conclude by employing the method to exhibit aspects of dispersive pulse propagation in a cold plasma, and suggest how predicted and experimental effects may be compared to improve the theoretical description of a medium's dispersive properties.Comment: 17 pages, 4 figures, RevTe

Diffractive orbits in isospectral billiards

Isospectral domains are non-isometric regions of space for which the spectra of the Laplace-Beltrami operator coincide. In the two-dimensional Euclidean space, instances of such domains have been given. It has been proved for these examples that the length spectrum, that is the set of the lengths of all periodic trajectories, coincides as well. However there is no one-to-one correspondence between the diffractive trajectories. It will be shown here how the diffractive contributions to the Green functions match nevertheless in a ''one-to-three'' correspondence.Comment: 20 pages, 6 figure

Biosafety and risk assessment in the use of genetically modified mosquitoes for disease control

The development and implementation of the release of genetically modified mosquitoes (GMM) for interrupting pathogen transmission represent a major challenge, despite the fact that several achievements have been made about Anopheles and Aedes mosquitoes. There are major biotechnology challenges remaining about the improvement of the stability of a gene construct and its expression for a robust and complete interruption of pathogen transmission and the devise of safe means of spreading foreign antipathogen genes through mosquito populations in the wild. The implementation obstacles to overcome include proper risk assessment and management, conduct of studies to ensure safety for humans and the environment, devise of appropriate control strategies based on sound gene-driving systems, address properly ethical, legal and social implications of the release of GMM and public concerns. Although the development of GMM as disease-control tool is technically feasible, for proper implementation no field release must be undertaken until clear scientific proof of safety for humans and the environment and efficacy is provided and ELSI concerns and public acceptance are properly addresse