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Two-fluid temperature-dependent relativistic waves in magnetized streaming pair plasmas
A relativistic two-fluid temperature-dependent approach for a streaming magnetized pair plasma is considered. Such a scenario corresponds to secondary plasmas created at the polar caps of pulsar magnetospheres. In the model the generalized vorticity rather than the magnetic field is frozen into the fluid. For parallel propagation four transverse modes are found. Two are electromagnetic plasma modes which at high temperature become light waves. The remaining two are Alfveacutenic modes split into a fast and slow mode. The slow mode is cyclotron two-stream unstable at large wavelengths and is always subluminous. We find that the instability cannot be suppressed by temperature effects in the limit of large (finite) magnetic field. The fast Alfveacuten mode can be superluminous only at large wavelengths, however it is always subluminous at high temperatures. In this incompressible approximation only the ordinary mode is present for perpendicular propagation. For oblique propagation the dispersion relation is studied for finite and large strong magnetic fields and the results are qualitatively described.Institute for Fusion Studie
Learning Ground Traversability from Simulations
Mobile ground robots operating on unstructured terrain must predict which
areas of the environment they are able to pass in order to plan feasible paths.
We address traversability estimation as a heightmap classification problem: we
build a convolutional neural network that, given an image representing the
heightmap of a terrain patch, predicts whether the robot will be able to
traverse such patch from left to right. The classifier is trained for a
specific robot model (wheeled, tracked, legged, snake-like) using simulation
data on procedurally generated training terrains; the trained classifier can be
applied to unseen large heightmaps to yield oriented traversability maps, and
then plan traversable paths. We extensively evaluate the approach in simulation
on six real-world elevation datasets, and run a real-robot validation in one
indoor and one outdoor environment.Comment: Webpage: http://romarcg.xyz/traversability_estimation
Physics Beyond the Standard Model: Focusing on the Muon Anomaly
We present a model based on the implication of an exceptional E_{6}-GUT
symmetry for the anomalous magnetic moment of the muon. We follow a particular
chain of breakings with Higgses in the 78 and 351 representations. We analyse
the radiative correction contributions to the muon mass and the effects of the
breaking of the so-called Weinberg symmetry. We also estimate the range of
values of the parameters of our model.Comment: 14 RevTeX pages, 5 figure
The Dark Energy Equation of State using Alternative High-z Cosmic Tracers
We propose to use alternative cosmic tracers to measure the dark energy
equation of state and the matter content of the Universe [w(z) & Omega_m]. Our
proposed method consists of two components: (a) tracing the Hubble relation
using HII galaxies which can be detected up to very large redshifts, z~4, as an
alternative to supernovae type Ia, and (b) measuring the clustering pattern of
X-ray selected AGN at a median redshift of z~1. Each component of the method
can in itself provide interesting constraints on the cosmological parameters,
especially under our anticipation that we will reduce the corresponding random
and systematic errors significantly. However, by joining their likelihood
functions we will be able to put stringent cosmological constraints and break
the known degeneracies between the dark energy equation of state (whether it is
constant or variable) and the matter content of the universe and provide a
powerful and alternative route to measure the contribution to the global
dynamics and the equation of state of dark energy. A preliminary joint analysis
of X-ray selected AGN (based on the largest to-date XMM survey; the 2XMM) and
the currently largest SNIa sample (Hicken et al.), using as priors a flat
universe and the WMAP5 normalization of the power-spectrum, provides:
Omega_m=0.27+-0.02 and w=-0.96+-0.07. Equivalent and consistent results are
provided by the joint analysis of X-ray selected AGN clustering and the latest
Baryonic Acoustic Oscillation measures, providing: Omega_m=0.27+-0.02 and
w=-0.97+-0.04.Comment: Different versions of this paper appear in the "Dark Universe"
conference (Paris, July 2009) and in the "1st Mediterranean Conference in
Classical & Quantum Gravity" (invited
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Bioinspired snapping-claw apparatus to study hydrodynamic cavitation effects on the corrosion of metallic samples
A creative low-cost and compact mechanical device that mimics the rapid closure of the pistol shrimp claw was used to conduct electrochemical experiments, in order to study the effects of hydrodynamic cavitation on the corrosion of aluminum and steel samples. Current-time curves show significant changes associated with local variations in dissolved O2 concentration, cavitation-induced erosion and changes in the nature of the surface corrosion products
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