Energy Functions in Box Ball Systems

The box ball system is studied in the crystal theory formulation. New conserved quantities and the phase shift of the soliton scattering are obtained by considering the energy function (or $H$-function) in the combinatorial $R$-matrix.Comment: 15 pages, LaTeX2e: one paragraph replaced and reference added in Introduction, a paragraph added in Section 2.5, remark 2) after Th 4.6 adde

Observation of an energetic radiation burst from mountain-top thunderclouds

During thunderstorms on 2008 September 20, a simultaneous detection of gamma rays and electrons was made at a mountain observatory in Japan located 2770 m above sea level. Both emissions, lasting 90 seconds, were associated with thunderclouds rather than lightning. The photon spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung gamma rays arriving from a source which is 60 - 130 m in distance at 90% confidence level. The observed electrons are likely to be dominated by a primary population escaping from an acceleration region in the clouds.Comment: 12 pages, 3 figures, accepted for publication in Physical Review Letter

Holographic storage of multiple coherence gratings in a Bose-Einstein condensate

We demonstrate superradiant conversion between a two-mode collective atomic state and a single-mode light field in an elongated cloud of Bose-condensed atoms. Two off-resonant write beams induce superradiant Raman scattering, producing two independent coherence gratings with a different wave vector in the cloud. By applying phase-matched read beams after a controllable delay, the gratings can be selectively converted into the light field also in a superradiant way. Due to the large cooperativity parameter and the small velocity width of the condensate, a high conversion efficiency of $> 70$ % and a long storage time of $> 120$ $\mu$s were achieved.Comment: 5 pages, 4 figure

Polar Perturbations of Self-gravitating Supermassive Global Monopoles

Spontaneous global symmetry breaking of O(3) scalar field gives rise to point-like topological defects, global monopoles. By taking into account self-gravity,the qualitative feature of the global monopole solutions depends on the vacuum expectation value v of the scalar field. When v < sqrt{1 / 8 pi}, there are global monopole solutions which have a deficit solid angle defined at infinity. When sqrt{1 / 8 pi} <= v < sqrt{3 / 8 pi}, there are global monopole solutions with the cosmological horizon, which we call the supermassive global monopole. When v >= sqrt{3 / 8 pi}, there is no nontrivial solution. It was shown that all of these solutions are stable against the spherical perturbations. In addition to the global monopole solutions, the de Sitter solutions exist for any value of v. They are stable against the spherical perturbations when v sqrt{3 / 8 pi}. We study polar perturbations of these solutions and find that all self-gravitating global monopoles are stable even against polar perturbations, independently of the existence of the cosmological horizon, while the de Sitter solutions are always unstable.Comment: 10 pages, 6 figures, corrected some type mistakes (already corrected in PRD version

Abelian Higgs Hair for Rotating and Charged Black Holes

We study the problem of vortex solutions in the background of rotating black holes in both asymptotically flat and asymptoticlly anti de Sitter spacetimes. We demonstrate the Abelian Higgs field equations in the background of four dimensional Kerr, Kerr-AdS and Reissner-Nordstrom-AdS black holes have vortex line solutions. These solutions, which have axial symmetry, are generalization of the Nielsen-Olesen string. By numerically solving the field equations in each case, we find that these black holes can support an Abelian Higgs field as hair. This situation holds even in the extremal case, and no flux-expulsion occurs. We also compute the effect of the self gravity of the Abelian Higgs field show that the the vortex induces a deficit angle in the corresponding black hole metrics.Comment: 22 pages, 16 figures, a section about the vortex self gravity on Kerr black hole added, extremal black holes considered, one figure changed, one reference adde

Cosmic Colored Black Holes

We present spherically symmetric static solutions (a particle-like solution and a black hole solution) in the Einstein-Yang-Mills system with a cosmological constant.Although their gravitational structures are locally similar to those of the Bartnik-McKinnon particles or the colored black holes, the asymptotic behavior becomes quite different because of the existence of a cosmological horizon. We also discuss their stability by means of a catastrophe theory as well as a linear perturbation analysis and find the number of unstable modes.Comment: 12 pages, latex, 4 figures (available upon request

Perturbations of global monopoles as a black hole's hair

We study the stability of a spherically symmetric black hole with a global monopole hair. Asymptotically the spacetime is flat but has a deficit solid angle which depends on the vacuum expectation value of the scalar field. When the vacuum expectation value is larger than a certain critical value, this spacetime has a cosmological event horizon. We investigate the stability of these solutions against the spherical and polar perturbations and confirm that the global monopole hair is stable in both cases. Although we consider some particular modes in the polar case, our analysis suggests the conservation of the "topological charge" in the presence of the event horizons and violation of black hole no-hair conjecture in asymptotically non-flat spacetime.Comment: 11 pages, 2 figures, some descriptions were improve