Plasma kinetics issues in an ESA study for a plasma laboratory in space

A study supported by the European Space Agency (ESA), in the context of its General Studies Programme, performed an investigation of the possible use of space for studies in pure and applied plasma physics, in areas not traditionally covered by ‘space plasma physics’. A set of experiments have been identified that can potentially provide access to new phenomena and to allow advances in several fields of plasma science. These experiments concern phenomena on a spatial scale (101–104 m) intermediate between what is achievable on the ground and the usual solar system plasma observations. Detailed feasibility studies have been performed for three experiments: active magnetic experiments, largescale discharges and long tether–plasma interactions. The perspectives opened by these experiments are discussed for magnetic reconnection, instabilities, MHD turbulence, atomic excited states kinetics, weakly ionized plasmas,plasma diagnostics, artificial auroras and atmospheric studies. The discussion is also supported by results of numerical simulations and estimates

Pseudogap formation of four-layer BaRuO3_3 and its electrodynamic response changes

We investiaged the optical properties of four-layer BaRuO$_{3}$, which shows a fermi-liquid-like behavior at low temperature. Its optical conductivity spectra clearly displayed the formation of a pseudogap and the development of a coherent peak with decreasing temperature. Temperature-dependences of the density $n$ and the scattering rate $1/\tau$ of the coherent component were also derived. As the temperature decreases, both $n$ and $1/\tau$ decrease for four-layer BaRuO$_{3}$. These electrodynamic responses were compared with those of nine-layer BaRuO$_{3}$, which also shows a pseudogap formation but has an insulator-like state at low temperature. It was found that the relative rates of change of both $n$ and $1/\tau$ determine either metallic or insulator-like responses in the ruthenates. The optical properties of the four-layer ruthenate were also compared with those of other pseudogap systems, such as high $T_{c}$ cuprates and heavy electron systems.Comment: 7 figures. submitted to Phys. Rev.

The influence of the viewpoint in a self-avatar on body part and self-localization

The goal of this study is to determine how a self-avatar in virtual reality, experienced from different viewpoints on the body (at eye- or chest-height), might influence body part localization, as well as self-localization within the body. Previous literature shows that people do not locate themselves in only one location, but rather primarily in the face and the upper torso. Therefore, we aimed to determine if manipulating the viewpoint to either the height of the eyes or to the height of the chest would influence self-location estimates towards these commonly identified locations of self. In a virtual reality (VR) headset, participants were asked to point at sev- eral of their body parts (body part localization) as well as "directly at you" (self-localization) with a virtual pointer. Both pointing tasks were performed before and after a self-avatar adaptation phase where participants explored a co-located, scaled, gender-matched, and animated self-avatar. We hypothesized that experiencing a self-avatar might reduce inaccuracies in body part localization, and that viewpoint would influence pointing responses for both body part and self-localization. Participants overall pointed relatively accurately to some of their body parts (shoulders, chin, and eyes), but very inaccurately to others, with large undershooting for the hips, knees, and feet, and large overshooting for the top of the head. Self-localization was spread across the body (as well as above the head) with the following distribution: the upper face (25%), the up- per torso (25%), above the head (15%) and below the torso (12%). We only found an influence of viewpoint (eye- vs chest-height) during the self-avatar adaptation phase for body part localization and not for self-localization. The overall change in error distance for body part localization for the viewpoint at eye-height was small (M = –2.8 cm), while the overall change in error distance for the viewpoint at chest-height was significantly larger, and in the upwards direction relative to the body parts (M = 21.1 cm). In a post-questionnaire, there was no significant difference in embodiment scores between the viewpoint conditions. Most interestingly, having a self-avatar did not change the results on the self-localization pointing task, even with a novel viewpoint (chest-height). Possibly, body-based cues, or memory, ground the self when in VR. However, the present results caution the use of altered viewpoints in applications where veridical position sense of body parts is required

Randomness Increases Order in Biological Evolution

n this text, we revisit part of the analysis of anti-entropy in Bailly and Longo (2009} and develop further theoretical reflections. In particular, we analyze how randomness, an essential component of biological variability, is associated to the growth of biological organization, both in ontogenesis and in evolution. This approach, in particular, focuses on the role of global entropy production and provides a tool for a mathematical understanding of some fundamental observations by Gould on the increasing phenotypic complexity along evolution. Lastly, we analyze the situation in terms of theoretical symmetries, in order to further specify the biological meaning of anti-entropy as well as its strong link with randomness

Milagro limits and HAWC sensitivity for the rate-density of evaporating Primordial Black Holes

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On the sensitivity of the HAWC observatory to gamma-ray bursts

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles