Thin structures and slender structures span more than ten orders of magnitude in scale; the examples include arches, buildings, toys, plants, and, down to micro-scales, membranes, flagella and cilia. Although the solid mechanics to describe such structures has a long history of studies over a few centuries, its new paradigm relevant to form, geometry and functionality is currently growing in physics communities. In this article, we review a modern framework for mechanics of slender structures and recent advances, highlighting the underlying common themes in seemingly disparate fields in physics.
We are searching for a CP-violating rare decay of the neutral kaon: KL0→π0νν(¯) at the Japan Proton Accelerator Research Complex (J-PARC) to explore new physics beyond the Standard Model in the particle physics. Based on the data taken in 2015, we set an upper limit on the branching ratio of 3×10-9 at the 90% confidence level; improving the current world record by an order of magnitude. This is just the first step of our quest for new physics beyond the Standard Model. We will continue exploring uncharted territory by increasing the beam intensity, and by upgrading our detector based on the knowledge obtained at each sensitivity level.
Graphene played a key historical role in the development of topological insulators (TIs)―materials that exhibit an electrically inert interior yet form exotic metals at their boundary. However, realization of the TI state and quantum-spin-Hall effect in graphene devices has remained an outstanding challenge dating back to the inception of the field of TIs. Graphene’s exceptionally weak spin-orbit coupling—stemming from carbon’s low mass―poses the primary obstacle. We experimentally and theoretically study artificially enhanced spin-orbit coupling in graphene via random decoration with dilute Bi2Te3 nanoparticles. Remarkably, multi-terminal resistance measurements suggest the presence of helical edge states characteristic of a quantum-spin-Hall phase; the magnetic-field and temperature dependence of the resistance peaks, X-ray photoelectron spectra, scanning tunneling spectroscopy, and first-principles calculations further support this scenario. These observations highlight a pathway to spintronics and quantum-information applications in graphene-based quantum-spin-Hall platforms.
We study the ΩΩ system in the 1S0 channel on the basis of the (2+1)-flavor lattice QCD simulations using a large volume (8.1 fm)3 and nearly physical pion mass mπ≃146 MeV. The obtained ΩΩ interaction is qualitatively similar to the central potential of the nucleon-nucleon interaction, i.e., the short range repulsion and the intermediate range attraction. We show that the attraction leads to the most strange dibaryon, di-Omega, which is located near the unitary limit. Such a system can be searched experimentally by two-Ω correlation in relativistic heavy-ion collisions.
The atomic nucleus has shell structures for both protons and neutrons with significant energy gaps occurring at particular occupation numbers. These numbers are called “magic numbers”, in analogy to the shell structure of noble gases in atomic physics. The magic numbers, which are 2, 8, 20, 28, 50, 82 and 126 protons or neutrons, suggested by Mayer and Jensen are well established in nuclei on or near the valley of stability. However, far from the valley of stability, these magic numbers can change in nuclei with a large excess of neutrons. The previous researches make it evident that the traditional shell closures at 8, 20, and 28 disappear, and that new ones at 16 and 32 are known to emerge. Here, we report on a study of the emergence of new magic number 34. The magic number 34 was predicted by a nuclear theory that well reproduces an occurrence of the magic number 16. The first experimental indication was reported by in-beam γ-ray spectroscopy of 54Ca. To identify whether magic number 34 emerges, we performed the first direct mass measurements of neutron-rich calcium isotopes beyond neutron number of 34 at the RIKEN RI Beam Factory by using the magnetic-rigidity time-of-flight technique. The atomic mass excesses of 55-57Ca were determined for the first time and provide an energy difference in Ca isotopes between neutron 2p1/2 and 1f5/2 orbitals. The experimental results identify the experimental signature of a sizable energy gap in 54Ca.