The discovery of high-energy cosmic neutrinos has opened up a new window on the Universe, and led to the dawn of high-energy neutrino astrophysics. Their origin is a new mystery in astroparticle physics, and solving this problem allows us not only to understand the physics of astrophysical sources but also to obtain important clues about the old mystery, the origin of cosmic rays, and to utilize neutrinos as probes of neutrino properties, dark matter, and fundamental physics. I summarize the latest results of IceCube observations and consider their implications for the sources of high-energy cosmic neutrinos. In particular, I show the importance of multi-messenger approaches, and discuss mysterious cosmic particle connections among neutrinos, gamma rays, and cosmic rays.
Experimental quest for the hypothetical “quantum spin liquid” state has recently met several promising candidate materials. We argue that many of these quantum spin liquids, including triangular-lattice organic salts and kagome-lattice herbertsmithite, might be the randomness-induced ones, either of extrinsic origin due to the impurities and defects, or of intrinsic origin spontaneously generated via the coupling between the spin and other degrees of freedom such as the charge. Recent numerical results on the random s=1/2 Heisenberg model on the triangular and kagome-lattices are reviewed. Implications to recent experiments are discussed.
X-ray astronomy satellite Hitomi is briefly described. Results of the measurement of the hot-gas velocity in the Perseus cluster of galaxies are reported. The observed turbulent velocity (164±10 km s-1 in the line of sight) infers that the turbulent pressure is only 4% of the thermodynamic one, and a velocity shear of 150±70 km s-1 over a scale of 200, 000 ly is also observed. The total mass of clusters based on hydrostatic equilibrium would require little correction for turbulent pressure. Even the satellite lost its function in about a month in the orbit, the result shows the power of microcalorimeters and the importance of high-resolution spectroscopy in future X-ray observations.