Core structure of EAS in 10(15) to 10(17) eV

With the use of Akeno calorimeter, the attenuation of particles in concrete is analyzed as the function of the shower size of 10 to the 5th power to 10 to the 7th power. The attenuation length does not depend much on the shower size but depends a little on the shower age. The average value is approx. 150 g/sq cm for s = 0.5 to 0.85 and approx. 40 g/sq cm for s = 0.85 to 1.15. These values and their fluctuations are consistent with the equi-intensity curves of extensive air showers (EAS)

Scale locality of the energy cascade using real space quantities

The classical energy cascade in turbulence as described by Richardson and Kolmogorov is predominantly a conjecture relying on the locality of interactions between scales of turbulence. This picture is generally accepted and assumes that energy and enstrophy transfers occur between neighbouring scales of turbulence and that vortex stretching plays a major role in the dynamics of this energy cascade. Direct numerical simulation data for Re_λ ranging from 37 to 1131 is used to gather evidence for the cascade by investigating the energy and enstrophy fluxes between scales and the interplay between vorticity at one scale and strain at an adjacent scale. This is achieved by using a bandpass filter to educe the turbulent structures at various length scales allowing one to determine the fluxes between these scales and to interrogate the role of non-local (in physical-space) vortex stretching. It is shown that the structures of a length scale L mostly transfer their energy to structures of size 0.3L and that most of the enstrophy flux goes from structures of scale L to 0.3L. Furthermore, vortical structures of a length scale L_ω are stretched mostly by straining structures of size 3 to 5L_ω and the stretching by eddies of sizes larger than 10L_ω is negligible. The stretching is dominated by the most extensive principal strain rate of the straining structures. These observations are found to be independent of Re_λ for the range investigated in this study. These results provide strong evidence for the classical view of an energy cascade transferring energy from large to small scales through a hierarchy of steps, each step consisting of the stretching of vortices by somewhat larger structures.Qualcomm European Research Studentship Fund in Technolog

Computing Storyline Visualizations with Few Block Crossings

Storyline visualizations show the structure of a story, by depicting the interactions of the characters over time. Each character is represented by an x-monotone curve from left to right, and a meeting is represented by having the curves of the participating characters run close together for some time. There have been various approaches to drawing storyline visualizations in an automated way. In order to keep the visual complexity low, rather than minimizing pairwise crossings of curves, we count block crossings, that is, pairs of intersecting bundles of lines. Partly inspired by the ILP-based approach of Gronemann et al. [GD 2016] for minimizing the number of pairwise crossings, we model the problem as a satisfiability problem (since the straightforward ILP formulation becomes more complicated and harder to solve). Having restricted ourselves to a decision problem, we can apply powerful SAT solvers to find optimal drawings in reasonable time. We compare this SAT-based approach with two exact algorithms for block crossing minimization, using both the benchmark instances of Gronemann et al. and random instances. We show that the SAT approach is suitable for real-world instances and identify cases where the other algorithms are preferable.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Magnetic monopole search by 130 m(2)sr He gas proportional counter

A search experiment for cosmic ray magnetic monopoles was performed by means of atomic induction mechanism by using He mixture gas proportional counters of the calorimeter (130 square meters sr) at the center of the Akeno air shower array. In 3,482 hours operation no monopole candidate was observed. The upper limit of the monopole flux is 1.44 x 10 to the minus 13th power cm-z, sec -1, sr-1 (90% C.L.) for the velocity faster than 7 x 0.0001 c

On the existence of a static black hole on a brane

We study a static black hole localized on a brane in the Randall-Sundrum (RS) II braneworld scenario. To solve this problem numerically, we develop a code having the almost 4th-order accuracy. This code derives the highly accurate result for the case where the brane tension is zero, i.e., the spherically symmetric case. However, a nonsystematic error is detected in the cases where the brane tension is nonzero. This error is irremovable by any systematic methods such as increasing the resolution, setting the outer boundary at more distant location, or improving the convergence of the numerical relaxation. We discuss the possible origins for the nonsystematic error, and conclude that our result is naturally interpreted as the evidence for the nonexistence of solutions to this setup, although an "approximate" solution exists for sufficiently small brane tension. We discuss the possibility that the black holes produced on a brane may be unstable and lead to two interesting consequences: the event horizon pinch and the brane pinch.Comment: 26 pages, 9 figures, submitted to JHE