Dynamical Casimir effect in curved spacetime

A boundary undergoing relativistic motion can create particles from quantum vacuum fluctuations in a phenomenon known as the dynamical Casimir effect. We examine the creation of particles, and more generally the transformation of quantum field states, due to boundary motion in curved spacetime. We provide a novel method enabling the calculation of the effect for a wide range of trajectories and spacetimes. We apply this to the experimental scenario used to detect the dynamical Casimir effect, now adopting the Schwarzschild metric, and find novel resonances in particle creation as a result of the spacetime curvature. Finally, we discuss a potential enhancement of the effect for the phonon field of a Bose-Einstein condensate.Comment: 17 pages, 0 figures, 2 appendice

Additions, combinations, and synonyms for the Bolivian moss flora

Fifty-five mosses are newly recorded for Bolivia. Additional collection data are given for twelve mosses considered little known or rare in the country. Six new synonyms are recognized, five from Bolivia, one from Brazil: Hookeria scabripes Müll. Hal. [Callicostella scabripes (Müll. Hal.) Broth.] = Callicostella pallida (Hornsch.) Ångstr.; Leucobryum fragile Herzog = Leucobryum subobtusifolium (Broth.) B.H. Allen; Macromitrium pinnulatum Herzog = Macromitrium microstomum (Hook. & Grev.) Schwägr.; Schlotheimia vesiculata Herzog [Macromitrium vesiculatum (Herzog) Herzog] = Macromitrium stellulatum (Hornsch.) Brid.; Cyclodictyon breve Herzog = Cyclodictyon albicans (Hedw.) Kuntze; and from Brazil: Callicostella paludicola Broth. = Callicostella merkelii (Hornsch.) A. Jaeger. Three new combinations are proposed: Entosthodon subaloma (Herzog) S.P. Churchill (Goniobryum subaloma Herzog), Syntrichia xerophila (Herzog) S.P. Churchill (Tortula xerophila Herzog), Thamniopsis lepidopiloides (Herzog) S.P. Churchill (Hookeriopsis lepidopiloides Herzog)

Inelastic collisions in an exactly solvable two-mode Bose-Einstein Condensate

Inelastic collisions occur in Bose-Einstein condensates, in some cases, producing particle loss in the system. Nevertheless, these processes have not been studied in the case when particles do not escape the trap. We show that such inelastic processes are relevant in quantum properties of the system such as the evolution of the relative population, the self trapping effect and the probability distribution of particles. Moreover, including inelastic terms in the model of the two-mode condensate allows for an exact analytical solution. Using this solution, we show that collisions favor the generation of entanglement between the modes of the condensate as long as the collision rate does not exceed the natural frequency of the system

Are constant loop widths an artifact of the background and the spatial resolution?

We study the effect of the coronal background in the determination of the diameter of EUV loops, and we analyze the suitability of the procedure followed in a previous paper (L\'opez Fuentes, Klimchuk & D\'emoulin 2006) for characterizing their expansion properties. For the analysis we create different synthetic loops and we place them on real backgrounds from data obtained with the Transition Region and Coronal Explorer (\textit{TRACE}). We apply to these loops the same procedure followed in our previous works, and we compare the results with real loop observations. We demonstrate that the procedure allows us to distinguish constant width loops from loops that expand appreciably with height, as predicted by simple force-free field models. This holds even for loops near the resolution limit. The procedure can easily determine when loops are below resolution limit and therefore not reliably measured. We find that small-scale variations in the measured loop width are likely due to imperfections in the background subtraction. The greatest errors occur in especially narrow loops and in places where the background is especially bright relative to the loop. We stress, however, that these effects do not impact the ability to measure large-scale variations. The result that observed loops do not expand systematically with height is robust.Comment: Accepted for publication in Ap

Continuous Forest Fire Propagation in a Local Small World Network Model

This paper presents the development of a new continuous forest fire model implemented as a weighted local small-world network approach. This new approach was designed to simulate fire patterns in real, heterogeneous landscapes. The wildland fire spread is simulated on a square lattice in which each cell represents an area of the land's surface. The interaction between burning and non-burning cells, in the present work induced by flame radiation, may be extended well beyond nearest neighbors. It depends on local conditions of topography and vegetation types. An approach based on a solid flame model is used to predict the radiative heat flux from the flame generated by the burning of each site towards its neighbors. The weighting procedure takes into account the self-degradation of the tree and the ignition processes of a combustible cell through time. The model is tested on a field presenting a range of slopes and with data collected from a real wildfire scenario. The critical behavior of the spreading process is investigated

Firm Strategy and Foreign Direct Investment: An Examination of the Economic Performance of U.S. Multinational Firms

International Relations/Trade, Production Economics,

Body image distortions following spinal cord injury

Background: Following spinal cord injury (SCI) or anaesthesia, people may continue to experience feelings of the size, shape, and posture of their body, suggesting that the conscious body image is not fully determined by immediate sensory signals. How this body image is affected by changes in sensory inputs from, and motor outputs to the body remains unclear. Methods: We tested paraplegic and tetraplegic SCI patients on a task that yields quantitative measures of body image. Participants were presented with an anchoring stimulus on a computer screen and told to imagine that the displayed body part was part of a standing mirror image of themselves. They then identified the position on the screen, relative to the anchor, where each of several parts of their body would be located. Veridical body dimensions were identified based on measurements and photographs of participants. Results: Compared to age-matched controls, paraplegic and tetraplegic patients alike perceived their torso and limbs as elongated relative to their body width. No effects of lesion level were found. Conclusions: The common distortions in body image across patient groups, despite differing SCI levels, imply that a body image may be maintained despite chronic sensory and motor loss. Systematic alterations in body image follow SCI, though our results suggest these may reflect prolonged changes in body posture and wheelchair use, rather than loss of specific sensorimotor pathways. These findings provide new insight into how the body image is maintained, and may prove useful in treatments that intervene to manipulate the body image

Sum-of-squares of polynomials approach to nonlinear stability of fluid flows: an example of application

With the goal of providing the first example of application of a recently proposed method, thus demonstrating its ability to give results in principle, global stability of a version of the rotating Couette flow is examined. The flow depends on the Reynolds number and a parameter characterising the magnitude of the Coriolis force. By converting the original Navier-Stokes equations to a finite-dimensional uncertain dynamical system using a partial Galerkin expansion, high-degree polynomial Lyapunov functionals were found by sum-of-squares-of-polynomials optimization. It is demonstrated that the proposed method allows obtaining the exact global stability limit for this flow in a range of values of the parameter characterising the Coriolis force. Outside this range a lower bound for the global stability limit was obtained, which is still better than the energy stability limit. In the course of the study several results meaningful in the context of the method used were also obtained. Overall, the results obtained demonstrate the applicability of the recently proposed approach to global stability of the fluid flows. To the best of our knowledge, it is the first case in which global stability of a fluid flow has been proved by a generic method for the value of a Reynolds number greater than that which could be achieved with the energy stability approach

2D kinematics of the edge-on spiral galaxy ESO 379-G006

We present a kinematical study of the nearly edge-on galaxy ESO 379-G006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H-alpha, we study the kinematics of ESO 379-G006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-G006 as well as the kinematic asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar Diffuse Ionized Gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that the extraplanar gas could lag in rotation velocity with respect to the midplane rotation.Comment: 61 pages, 15 figures. Accepted for publication in A