Vacuum Structure and Dark Energy

We consider that the universe is trapped in an excited vacuum state and the resulting excitation energy provides the observed dark energy. We explore the conditions under which this situation can arise from physics already known. Considering the example of how macroscopic QED fields alter the vacuum structure, we find that the energy scale 1 meV --- 1 eV is particularly interesting. We discuss how dark energy of this form is accessible to laboratory experiments.Comment: 5 pages, 2 figures; recognized for Honorable Mention in 2010 Gravity Research Foundation Awards for Essays on Gravitation, in press with Int. J. Mod. Phys.

A Nonliearly Dispersive Fifth Order Integrable Equation and its Hierarchy

In this paper, we study the properties of a nonlinearly dispersive integrable system of fifth order and its associated hierarchy. We describe a Lax representation for such a system which leads to two infinite series of conserved charges and two hierarchies of equations that share the same conserved charges. We construct two compatible Hamiltonian structures as well as their Casimir functionals. One of the structures has a single Casimir functional while the other has two. This allows us to extend the flows into negative order and clarifies the meaning of two different hierarchies of positive flows. We study the behavior of these systems under a hodograph transformation and show that they are related to the Kaup-Kupershmidt and the Sawada-Kotera equations under appropriate Miura transformations. We also discuss briefly some properties associated with the generalization of second, third and fourth order Lax operators.Comment: 11 pages, LaTex, version to be published in Journal of Nonlinear Mathematical Physics, has expanded discussio

A proof of Jarzynski's non-equilibrium work theorem for dynamical systems that conserve the canonical distribution

We present a derivation of the Jarzynski identity and the Crooks fluctuation theorem for systems governed by deterministic dynamics that conserves the canonical distribution such as Hamiltonian dynamics, Nose-Hoover dynamics, Nose-Hoover chains and Gaussian isokinetic dynamics. The proof is based on a relation between the heat absorbed by the system during the non-equilibrium process and the Jacobian of the phase flow generated by the dynamics.Comment: 12 page

Individual variation in EEG spectral power enhancement and intelligence

This study tested the relationship between short-term neuroplasticity and individual differences in intelligence. Twenty-two participants completed cognitive testing and a visual EEG experiment involving exposures to repeated and novel stimuli. Time-frequency analyses of phase-locked (evoked) and non-phase-locked (induced) power showed a small effect of decreasing evoked/induced theta (4-8 Hz) ratios over stimulus exposures, irrespective of condition. Hypotheses that intelligence would relate to an increase in this ratio over exposures were not supported. However, the magnitude of the ratio positively correlated with intelligence; while the amount of induced gamma (30-50Hz) activation pre- to post-stimulus was highly inversely related to g. Results suggest that transient changes in neural network phase strongly relate to intelligence in physiological measurements acquired over brief intervals

Photon-Photon Interaction in a Photon Gas

Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in non-equilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an application we consider the interaction of photons with the cosmic microwave background radiation.Comment: REVTEX, 7 pages, 1 PostSrcipt figur

The use of high-resolution terrain data in gravity field prediction

Different types of gravity prediction methods for local and regional gravity evaluation are developed, tested, and compared. Four different test areas were particularly selected in view of different prediction requirements. Also different parts of the spectrum of the gravity field were considered

Robotic control of the seven-degree-of-freedom NASA laboratory telerobotic manipulator

A computationally efficient robotic control scheme for the NASA Laboratory Telerobotic Manipulator (LTM) is presented. This scheme utilizes the redundancy of the seven-degree-of-freedom LTM to avoid joint limits and singularities. An analysis to determine singular configurations is presented. Performance criteria are determined based on the joint limits and singularity analysis. The control scheme is developed in the framework of resolved rate control using the gradient projection method, and it does not require the generalized inverse of the Jacobian. An efficient formulation for determining the joint velocities of the LTM is obtained. This control scheme is well suited for real-time implementation, which is essential if the end-effector trajectory is continuously modified based on sensory feedback. Implementation of this scheme on a Motorola 68020 VME bus-based controller of the LTM is in progress. Simulation results demonstrating the redundancy utilization in the robotic mode are presented

Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living supra-specific taxa of Chondrichthyan fishes. Part B: Batomorphii. 4a: Order Rajiformes - Suborder Myliobatoidei - Superfamily Dasyatoidea - Family Dasyatidae - Subfamily Dasyatinae - Genera: <i>Amphotistius, Dasyatis, Himantura, Pastinachus, Pteroplatytrygon, Taeniura, Urogymnus</i> and <i>Urolophoides</i> (incl. supraspecific taxa of uncertain status and validity), Superfamily Myliobatoidea - Family Gymnuridae - Genera: <i>Aetoplatea</i> and <i>Gymnura</i>, Superfamily Plesiobatoidea - Family Hexatrigonidae - Genus: <i>Hexatrygon</i>

Part B of this series, comprising the Batomorphii is continued with taxa of the Myliobatoidei. The tooth morphology of representatives of eight genera (incl. supraspecific taxa of uncertain status and validity) of the family Dasyatidae, two of Gymnuridae and one of Hexatrygonidae is described and illustrated by SEM-photographs. A differential diagnosis for a final conclusions on myliobatoid odontology will be given in a forthcoming issue dealing with the last myliobatoid taxa