Fundamental properties of neutrinos such as the Majorana nature and the neutrino mass beyond the standard model are studied by neutrino-less double beta decays (DBD). Properties of astro-neutrinos and supernova neutrino nucleosyntheses are studied by astro-neutrino nuclear reactions (inverse-beta decays). Neutrino nuclear responses for DBDs and astro-neutrinos are crucial for these studies of neutrinos in nuclei. This is a brief review on recent experimental studies of neutrino nuclear responses for DBDs and astro-neutrinos by means of charge-exchange nuclear and leptonic reactions and others. The quenching of the axial-vector response with respect to the QRPA model response is discussed.
Quantum information theory has been successfully applied to various fields of fundamental physics. Relative entropy is one of the central concepts of quantum information theory, which defines a distance measure with nice properties in the space of density matrices. In this article, we review selected examples of the applications of relative entropy to high energy physics, quantum theory of gravity, and nonequilibrium physics.
Thermal conductivity κ of black phorphorus and graphite are investigated. A faster evolution of κ than specific heat is resolved in both systems. We argue that the most important requirement for phonon hydrodynamics is peculiar phonon dispersion which enhances low-energy phonon density-of-states. Thinning of a graphite sample substantially increases the thermal conductivity. The thinnest sample with a few micrometers conducts heat better than diamond. A satisfactory account of this observation is lacking.
Electronic properties of an organic superconductor λ-(BETS)2 GaCl4 were investigated by 13C and 69,71Ga-NMR spectroscopy. We found that the spin-density-wave phase is adjacent to the superconducting (SC) phase. In addition, 69,71Ga-NMR results suggested that the enhancement of (T1T)-1 observed in the SC salt is due to a magnetic origin, confirming the existence of spin-density-wave fluctuation even just above Tc . In the presence of such spin fluctuations, the SC wave function is found to be a spin singlet with line nodes on the SC gap, which can be explained by the d-wave symmetry.
Thorium-229 (Th-229) has the lowest energy excited state of ～8.3 eV among thousands of nuclei. Its energy level is low enough to be excited optically by a laser and thus could be utilized as an ultra-precise “nuclear clock”. Despite of many years research, there was no successful laser excitation so far. This was primarily due to the difficulty in freely accessing the isomeric state. We have developed a novel method of producing the isomeric state using synchrotron radiation X-ray. This method enables us to produce plenty of the isomeric states with a controllable manner, which would accelerate a study towards realization of “nuclear clock”.