Note on: "Domain wall universe in the Einstein--Born--Infeld theory" Phys. Lett. B 679 (2009) 160

The interaction between bulk and dynamic domain wall in the presence of a linear / non-linear electromagnetism make energy density, tension and pressure on the wall all variables, depending on the wall position. In [1] this fact seems to be ignored.Comment: 4 pages, 1 figur

Dynamics of abelian subgroups of GL(n, C): a structure's Theorem

In this paper, we characterize the dynamic of every abelian subgroups $\mathcal{G}$ of GL($n$, $\mathbb{K}$), $\mathbb{K} = \mathbb{R}$ or $\mathbb{C}$. We show that there exists a $\mathcal{G}$-invariant, dense open set $U$ in $\mathbb{K}^{n}$ saturated by minimal orbits with $\mathbb{K}^{n}- U$ a union of at most $n$ $\mathcal{G}$-invariant vectorial subspaces of $\mathbb{K}^{n}$ of dimension $n-1$ or $n-2$ on $\mathbb{K}$. As a consequence, $\mathcal{G}$ has height at most $n$ and in particular it admits a minimal set in $\mathbb{K}^{n}-\{0\}$.Comment: 16 page

Evaluating Adaptability in ASD Classrooms: Study conducted in Egypt

87% of children on the Autism Spectrum display signs of sensory abnormalities thus interact differently with the built environment. To create better environments, guidelines suggest designing adaptable spaces to better correlate with the students’ needs yet there is no set system to evaluate adaptability. This paper aims to develop an adaptability evaluation metric for classrooms that accommodate for students on the spectrum. Drawing upon the definition of adaptability, recommendations from the literature are compiled and verified by teachers in order to understand what aspects should be adaptable and how. Once the points are defined the evaluation metric is developed. Following BREEAM’s variable weighting system, the weighting system for this guideline is based on teachers’ responses on the seriousness and impact of classroom features on the occupants and teaching process. The results from the weighting questionnaire show that lights have the most impact followed by furniture, layout and surfaces. However, the difference between the aspect with highest weighting and aspect with lowest weighting was only 5% meaning that all aspects should be attended to. Following the pre-processing, 5 centres accommodating for ASD students and 1 classroom with only neurotypicals (NT) are evaluated to test the metric and see where it lacks. The NT classroom achieved 46% and the highest classroom achieved 71%. Although no centre had advanced lighting controls, the rest of the criteria were present in at least 1 centre. Finally, interviews with 3 heads of centres were undertaken to understand what aspects they believe this metric would help with. The main benefit from this guideline, as explained by the heads is the recommendations for improvement, therefore the results presented are set as potential for improvement rather than awarding excellence. This paper presents a draft adaptability metric that needs further improvement by increasing number of criteria and verifying weighting values

Resource targets for advanced underground coal extraction systems

Resource targets appropriate for federal sponsorship of research and development of advanced underground coal mining systems are identified. A comprehensive examination of conventional and unconventional coals with particular attention to exceptionally thin and thick seams, steeply dipping beds, and multiple seam geometry was made. The results indicate that the resource of primary importance is flat lying bituminous coal of moderate thickness, under moderate cover, and located within the lower 48 states. Resources of secondary importance are the flat lying multiple seams and thin seams (especially those in Appalachia). Steeply dipping coals, abandoned pillars, and exceptionally thick western coals may be important in some regions of subregions, but the limited tonnage available places them in a position of tertiary importance

Recovering Classical Dynamics from Coupled Quantum Systems Through Continuous Measurement

We study the role of continuous measurement in the quantum to classical transition for a system with coupled internal (spin) and external (motional) degrees of freedom. Even when the measured motional degree of freedom can be treated classically, entanglement between spin and motion causes strong measurement back action on the quantum spin subsystem so that classical trajectories are not recovered in this mixed quantum classical regime. The measurement can extract localized quantum trajectories that behave classically only when the internal action also becomes large relative to ħ

Ground State H-Atom in Born-Infeld Theory

Within the context of Born-Infeld (BI) nonlinear electrodynamics (NED) we revisit the non-relativistic, spinless H-atom. The pair potential computed from the Born-Infeld equations is approximated by the Morse type potential with remarkable fit over the critical region where the convergence of both the short and long distance expansions slows down dramatically. The Morse potential is employed to determine both the ground state energy of the electron and the BI parameter.Comment: 4 pages, 1 figure, final version to appear in Foundation of Physic

Subwavelength atom localization via amplitude and phase control of the absorption spectrum

We propose a scheme for subwavelength localization of an atom conditioned upon the absorption of a weak probe field at a particular frequency. Manipulating atom-field interaction on a certain transition by applying drive fields on nearby coupled transitions leads to interesting effects in the absorption spectrum of the weak probe field. We exploit this fact and employ a four-level system with three driving fields and a weak probe field, where one of the drive fields is a standing-wave field of a cavity. We show that the position of an atom along this standing wave is determined when probe field absorption is measured. We find that absorption of the weak probe field at a certain frequency leads to subwavelength localization of the atom in either of the two half-wavelength regions of the cavity field by appropriate choice of the system parameters. We term this result as sub-half-wavelength localization to contrast it with the usual atom localization result of four peaks spread over one wavelength of the standing wave. We observe two localization peaks in either of the two half-wavelength regions along the cavity axis.Comment: Accepted for publication to Physical Review

Modeling active electrolocation in weakly electric fish

In this paper, we provide a mathematical model for the electrolocation in weakly electric fishes. We first investigate the forward complex conductivity problem and derive the approximate boundary conditions on the skin of the fish. Then we provide a dipole approximation for small targets away from the fish. Based on this approximation, we obtain a non-iterative location search algorithm using multi-frequency measurements. We present numerical experiments to illustrate the performance and the stability of the proposed multi-frequency location search algorithm. Finally, in the case of disk- and ellipse-shaped targets, we provide a method to reconstruct separately the conductivity, the permittivity, and the size of the targets from multi-frequency measurements.Comment: 37 pages, 11 figure